synthesis and physico-chemical studies of thesi s · "synthesis and physico-chemical studies...

SYNTHESIS AND PHYSICO-CHEMICAL STUDIES OF TRANSITION METAL COMPLEXES INVOLVING

N AND S DONOR MOIETIES

T H E S I S SUBMITTED FOR THE AWARD OF THE DEGREE OF

Bottor of pjntogopljp IN

CHEMISTRY

BY

MANZOOR AHMAD RATHER

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH ( INDIA)

1998

T5259

THESIS

L^Acc. N

Azad L

1 2 JUL 2000

m& CB£' -S002

nnuj

Who is no more

aUr. Uanir. -At. ^J\nan

M.Sc.,Ph.D.(Alig.)

Fax No. Phone Talex

(0091) 0571-400466 0571(400515)

64-230-AMU-IN

DIVISION OF INORGANIC CHEMISTRY

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY ALIGARH -202002 (INDIA)

es^niviesiis

Certified that the work embodied in this thesis entitled

"Synthesis and Physico-Chemical Studies of Transition

Metal Complexes Involving N and S Donor Moieties" is the

result of original researches carried out by Mr. Manzoor

Ahmad Rather under my supervision and is suitable for

submission for the award of the Ph.D. degree of Aligarh

Muslim University, Aligarh.

( Dr .T.A. Khan )

DIVISION OF INORGANIC CHEMISTRY

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY ALIGARH-202002 (INDIA)

*? express my yrate^ullness cordially and relisAinaly to my

supervisor ^ ^ r . ^ f t h i f c^ \ l* o^h«»n {,or 6is invaluable assiduous

guidance. *t¥is persistent diligence and perseverance with prompt response

was courteous and sympathetic towards me throughout the tenure o£ this

research proaram.

'De^frite the impossibility a/ aivina credit to every one who has dee* o£

help. 0 would li6e to single tut certain people who have &eeu especially

instrumental, directly or indirectly in the completion o£ this work, /he

professional expertise and perspicuity 0^ fjtof. ^YY)> ^ b A f c l f - laced w uh

his keen interest in research, made it a remar&a^le and unfaraetaHe

achievement'.

*) aw privileged to than6 f3t of. *YY). yjlyns, Chairman.

'Department o£ Chemistry far providing necessary research facilities, *i¥is

unparalleled teaching at my post'-graduate level remained ad a. perennial

memory.

0 certainly appreciate the help and cooperation extended 6-y my

stimulating colleagues particularly 6y <&*. y$(*j\.f9* ~\?nvkey, ^fjed

^5. ^ASAo J^h«n ^$. v7slnm and (YQinnat ^hagufta in this endeavour. 1 hope none will fael sliahted &y the physical impossibility o£

listing every name. 1 have enjoyed a lot with my friends ^ A I D A I

1r lanzoor stywiad rCalh

M.Sc.,M.Phil.(Alig.)

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and otAei mem&ei& 0/ t6e family cv£a Aave cmttii&uted mue& tkiouaA t&ei*

innccmetadle tatii^iteA aver the yeatA including love and tufifroit morally a&

well at materially. f4yain at la&t &ut not lea&t 0 Have no <vaid& to exfueM

£o% my elder Ixotker MQt.Q/.IYQ. ^ A t b c r &4<t made me &6at *) am

today.

0 tveuld alia li6e to (6.0.16 "paiaf "TKetimetet (A'/fcfile - "Pie @&mfc ute*&) "pot, CfCvCtty ^Cttal &6a.fic (a tkii ttie&Ci.

MQctnxoor cA' f a t h e r

ABSTRACT

T his work deals with the synthesis and

structural studies of novel macrocyclic

complexes of transition metal ions (Mn", Co",

Ni", Cu"and Zn") and tin-transition metal

heterobimetal l ic complexes. Herein,

introductory chapter [1] embodies a succinct

account of the earlier work described in

literature and present objectives of undertaking

the studies in this area. The chapter [2] deals

AJbstract {'•• | l\

with the instruments used for characterizing the

various complexes. The chapter [3] describes

the basic experimental procedures, reagents used

to perform the synthesis of various metal

complexes and their results and discussion.

The first part [3.1] of the third chapter

deals with the synthesis and characterization of

a new series of heterobimetallic tin-transition

metal complexes: dichloro(l,2-diphenylethane-

1,2-dione bis l,2-diaminoethane)metal(II)-

dichlorotin(IV),[MCl;L'SnCl2]; dichloro(l,2-

diphenylethane-1.2-dione bis 1,3-diamino-

propane)metal(II) dichlorotin(IV), [MC12L2

SnCl2] [M = Mn11. Co", Ni", Cu" and Zn"];

dichloro(l,3-dimethylpropane-l,3-dione bis

1,2-diaminoethane)metal(II) dichlorotin(IV),

[MChL'SnCh] and dichloro(l,3-dimethyl

propane-l ,3-dione bis 1,3-diamino

p r o p a n e ) m e t a l ( I I ) - d i c h l o r o t i n ( I V ) ,

[MCl2L4SnCl2] [M= Mnn, Co11, Nin, Cu11 and

Zn11]. The reactions were carried out by treating

1,2-diaminoethane or 1,3-diaminopropane with

diketones (benzil or 2,4-pentanedione) in

presence of transition metal salts and tin(IV)

chloride in 2:1:1:1 molar ratio. The complexes

are stable to atmosphere at room temperature.

These compounds were characterized by using

a range of techniques including IR, 'H NMR,

EPR, electronic spectral studies, conductivity

and magnetic susceptibility measurements. The

elemental analyses results are acceptable with

the proposed stoichiometry of the complexes.

These adducts have very low solubility in

organic solvents, but are freely soluble in polar

solvents such as dimethylformamide,

dimethylsulphoxide and acetonitrile. All the

complexes gave molar conductance values

consistent with their non-electrolytic nature.

Q

The main feature of IR spectra is the

appearance of a band around 1600 cm'1 which

can be assigned to the azomethine linkage

v(C=N) and is consistent with coordinated imine

bonds. This information along with the absence

of bands due to carbonyl groups strongly support

that the condensation of primary amine with the

carbonyl group has taken place. The position

of another important v(N-H) band around

3170 cm'1 is in support of coordination through

amino nitrogen. The v(M-N) and v(Sn-N) bands

appeared around 450 cm"1 and 3 80 cm"1,

respectively. The complexes exhibit a broad

intense band in the 300-360 cm"1 region, which

may probably be associated with the v(Sn-Cl)

frequencies. The other vibrations appeared at

their expected positions. The 'H NMR spectra

of [ZnCl; (L'-L4)SnCl2] adducts appear to be

more complex and do not show any bands

assignable to primary amino protons. All the

compounds gave two multiplets between 6.08-

6.20 ppm and between 3.18-3.21 ppm which can

'' be assigned to the N-H protons (C-NH, 2H) and

the methylene (CH2-N, 8H) protons of amine

moiety, respectively. The 'H NMR spectra of

central methylene protons of 1,3-diamino-

propane and 2,4-pentanedione, phenyl ring

protons and imine methyls appear at their

respective positions. However, the broadness of

the 2.38 ppm band for the complex

[ZnCl2L4SnCl2] may be due to the overlapping

of middle methylene protons of 2,4-pen

tanedione and 1,3-diaminopropane. The EPR

spectra of copper(II) complexes exhibit g[ and

gx values in the range 2.23-2.28 and 2.10-2.14,

respectively, suggesting a distorted octahedral

structure around copper(II) ion. The spectral and

magnetic moment data support octahedral

Abstract

geometry for rest of the complexes.

The second part [3.2] of the chapter

presents the synthesis and characterization of

tetraoxotetraamide macrocyclic complexes:

dichloro/nitrato(6:7,14:15-dibenzo-5,9,12,16-

t e t r a o x o - l , 4 , 8 , 1 3 - t e t r a a z a c y c l o h e x a -

decane)metal(II), [ML5X2] [M = Mn11, Co", Ni",

Cu11 and Zn"; X = CI or N03] and dichloro/

nitrato(7:8,15:16-dibenzo-6,10,13,17 - tetraoxo

- 1,5,9,14-tetraazacycloheptadecane)metal(II),

[ML6X2] [M = Mn", Co", Ni", Cu" and Zn";

X = CI or NO?]. These complexes were derived

from anthranilic and succinic acids reacted with

1,2-diaminoethane or 1,3-diaminopropane in

presence of transition metal ions in 2:1:1:1 molar

ratio. The complexes are generally coloured and

polycrystalline in nature. They are obtained in

good yield and are stable in solid state. The low

molar conductance values suggest their non-

[[^Abstract ]jj: | l]

electrolytic nature.

The IR spectra of the complexes show a

medium intensity band in 3200-3240 cm'1 region j i ]

assigned to v(N-H) and appearance of a new | j

band in 400-440 cm"1 region ascribed to I

v(M-N) vibration. This plus the absence of bands

corresponding to primary amine and appearance

of amide bands provide strong evidence that the

cyclization has taken place. The ' H NMR spectra

of zinc(II) complexes show a broad signal in

the 8.41-8.46 ppm range assigned to amide

protons. This information along with the absence

of bands corresponding to the carboxylic or

primary amino protons support the

macrocyclization. The room temperature EPR

spectra ofthecopper(II) complexes gave g| and

gj. values in the 2.21-2.26 and 2.11-2.16 regions,

respectively, characteristic of octahedral

geometry having the unpaired electron in the

Abstract

dx2-y2 orbital. The spectral and magnetic

moment data are entirely consistent with six

coordination at the metal centres.

The third part [3.3] of the chapter reports

the synthesis and spectroscopic studies of

tetraiminetetraamide macrocyclic complexes:

dichloro/nitrato(6,7,14,15-tetraoxo-2,3,10,11 -

tetraphenyl-l,4,5,8,9,12,13,16-octaazacyclo-

hexadecane-1,3,9,1 l-tetraene)metal(II), [ML7

X2] [M = Mn", Co". Ni", Cu" and Zn"; X = CI

or NO?] and (6,7,14,15-tetraoxo-2,3,10,11-

tetraphenyl-1,4,5,8,9,12,13,16- octaazacyclo-

hexadecane-1,3.9,1 l-tet-raene)copper(II)

chloride/nitrate [CuL7] X2 [X = CI or N03]. The

complexes have been prepared by the

condensation reaction of 1,2-diphenylethane-

1,2-dione dihydrazone (DPEDDH) with

dimethyl or diethyloxalate followed by metal

templation in 2:2:1 molar ratio. Both starting

materials dimethyl and diethyl oxalate were used

with each metal leading to the identical products.

They are freely soluble in dimethylsulphoxide,

dimethylformamide and exhibit 1:1 metal to

ligand stoichiometry. The molar conductivities

indicate that copper(II) complexes are

electrolytic while others are non-electrolytic in

nature.

The most significant feature of IR

spectra of these complexes is the apprearance

of four characteristic amide bands in the 1680-

1715. 1510-1550, 1225-1255 and 635-670 cm"1

regions. The amide I, v(C=0) band is observed

in the region expected for metal-free amide

group ruling out the possibility of coordination

through amide oxygen. A single sharp secondary

amine band observed in the 3240-3275 cm'1

region, is similar to analogous metal-free

terraaza ligands which indicate that the amide

[j; Abstract , 10

nitrogens do not involve in coordination. The

complexes exhibit a strong intensity band in the

range of 1580-1595 cm"' assignable to the

coordinated v(C=N). There is observed increase

in the v(C=N) band intensity which may be due

to possible transformation of /ram-stucturure of

the free ligand (DPEDDH) into cis

configuration upon complexation. The 'H NMR

spectra of both the zinc(II) complexes showed

the appearance of a band at 8.42, 8.45 ppm

reasonably ascribed to amide (N-NH-C,4H)

protons. This information along with absence

of characteristic peaks corresponding to the

protons of hydrazone and oxalate moieties

further confirm that cyclization has indeed taken

place. The calculated g| and gx values of the

copper(Il) complexes appeared in the 2.31, 2.34

and 2.08, 2.09 regions, respectively, supporting

the contention that dx:-y: may be the ground

I

state of the unpaired electron and the complexes

are of ionic character. The spectral and magnetic

moment data suggest the square-planar geometry

around the copper(II) ions while other

complexes have octahedral geometry.

The fourth part [3.4] of the chapter

presents the synthesis and characterization of

bis(macrocyclic) complexes : dichloro/nitrato

[l,l'-phenylbis(3,6,9,12-tetrahydro-l,3,6,9,12-

pentaazacyclotridecane)metal(II), [M2L8X4]

[M = Mn", Co11, Nin, Cu" and Zn"; X = CI or

N03]; In these complexes two pentaazacyclo-

tetradecane subunits are linked by a biphenyl

group attached to an uncoordinated benzidine

nitrogen atom. The new series of

bis(macrocyclic) complexes have been

synthesized by the template reaction of metal

salt, benzidine, formaldehyde and triethylene-

tetraamine in 1:1:4:2 molar ratio. All complexes

[rAbstract'i,' | 121

are stable to atmosphere and are polycrystalline

in nature. Elemental analyses agree well with

the proposed structure. The molar conductance

values are supportive of non-electrolytic nature.

The most important feature of IR spectra

is that the complexes gave no bands assignable

to primary amino or carbonyl group stretching

modes. In all the complexes, a single sharp band

observed around 3210 cm"1 may be assigned to

v(N-H) of the coordinated secondary amino

group. These data strongly support the formation

of proposed macrocyclic moiety. The bands

around 1170 cm"1 assignable to v(C-N) vibration,

further confirm the suggested structure. The

*H NMR spectra of zinc(II) complexes show two

multiplets in 6.38, 6.41 ppm and 3.34, 3.36 ppm,

regions which correspond to the secondary

amino and methylene protons, respectively.

Another multiplet observed for both the

r

complexes in the 2.43, 2.46 and 7.23, 7.28 ppm

corresponds to the methylene protons of

triethylenetetraamine and aromatic ring

protons, respectively. More interestingly, no

band assignable to aldehydic or primary amino

protons is observed which strongly support the

concluded frame-work. The room temperature

EPR spectra of the copper(II) bis(macrocyclic)

complexes show g| andgi values at 2.25, 2.30

and 2.09, 2.14 respectively. In these

complexes, (gj < 2.3 and G < 4) is indicative of

the covalent nature and considerable exchange

interaction of the complexes. On the basis of

spectral and magnetic moment values an

octahedral geometry is proposed around the

metal ions.

The fifth part [3.5] of the chapter

describes synthesis and spectroscopic studies

of a new series of dithiadiaza macrocyclic

complexes :dichloro/nitrato( 1:2,7:8-dibenzo-

10,13-dioxo-3,6-dithia-9,14-diazacyclo-

tetradecane)metal(II), [ML9X2] [M = Co" or

Zn"; X = CI or N03]; (l:2,7:8-dibenzo-10,13-

d ioxo-3 ,6 -d i th ia -9 ,14-d iazacyc lo te t ra -

decane)metal(II) chloride/nitrate [ML9]X2 [M =

Nin or Cu"; X = CI or N03]; dichloro/nitrato

(1:2,7:8,11:12-tribenzo - 10,13 - dioxo - 3,6-

dithia-9,14-diazacyclotetradecane)metal(II),

[ML10X2] [M = Co" or Zn"; X = CI or N03] and

(1:2,7:8,11:12 - tribenzo - 10,13-dioxo-3,6-

dithia-9,14-diazacyclotetradecane)metal(II),

chloride/nitrate [ML,0]X2 [M = Ni" or Cu";

X = CI or NO:,]. These complexes were obtained

by the template condensation of metal salt,

1,2-ethane dithiol, o-bromoaniline and succinic

or phthalic acid in 1:1:2:1 molar ratio. The

complexes prepared have 1:1 metal to ligand

stoichiometry. The molar conductance values

Abstract [II [ 15

I I

indicate ionic nature of nickel(II) and copper(II)

complexes while cobalt(II) and zinc(II)

complexes exhibit their non-electrolytic nature.

The absence of IR bands characteristic

of thiol or hydroxyi groups and the appearance

of bands corresponding to an amide group

strongly suggest that the proposed ligand

frame-work is formed. In addition to this, bands

in the 395-420 and 330-370 cm"1 regions

assignable to v(M-N) and v(M-S) vibrations,

respectively, further confirm the proposed

structure. The other important vibrations

appeared at their respective positions. The

'H NMR spectra of zinc(II) complexes also show

the absence of carboxylic or thiol protons and

appearance of signals assignable to amide

protons which again confirm the proposed

frame-work. The EPR spectra of polycrystalline

copper(II) samples exhibited a strong single

i

Abstract 16

band with g( and gi values in the 2.32-2.37 and

2.09-2.12 ranges, respectively, indicating ionic

nature, which is well suited for electrolytic

nature of copper. The spectral and magnetic

moment values suggest that complexes derived

from nickel and copper have square-planar

geometry, while octahedral geometry is

proposed for cobalt and zinc complexes.

This project comes to an end with the

chapter [4] which concludes the work done.

LIST OF PUBLICATIONS

1) Spectroscopic studies of heterobimetallic adducts of Tin with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). T.A. Khan, M.A. Rather, S.P. Varkey, S.S. Hasan and M.Shakir, Main Gr. Met. Chem., 1996, 19(4), 225.

2) Tetraoxotetraamide macrocyclic complexes. T.A. Khan, M.A. Rather, N. Jahan, S.P. Varkey and M. Shakir, Transition Met. Chem., 1997 (in press).

3) Metal ion directed synthesis of tetraiminetetraamide macrocyclic complexes derived from 1,2-diphenylethane 1,2-dione dihydrazone. T.A. Khan and M.A. Rather, Supra. Mol. Chem., 1998 (Communicated).

4) Synthesis and characterisation of bis(macrocyclic) complexes based on the 13-membered pentaaza unit. T.A. Khan, M.A. Rather. N. Jahan, S.P. Varkey and M. Shakir, Synth. React. Inorg. Met.-Org. Chem., 1997, 27(6), 843.

5) Synthesis and spectroscopic studies of 14- membered dithiadiaza macrocyclic complexes of transition metal ions. T.A. Khan, M.A. Rather, A.K. Mohamed, K.S. Islam and M. Shakir, Coord. Chem., 1998 (Communicated).

CONTENTS

^CHAPTER FIRST GENERAL INTRODUCTION

1.1 References ^CHAPTER SECOND INSTRUMENTS USED

2.1 IR Spectroscopy 2.2 1H NMR Spectroscopy 2.3 EPR Spectroscopy 2.4 UV-V1S. Spectroscopy 2.5 Magnetic Susceptibility Measurements 2.6 Molar Conductance Measurements 2 7 Elemental Analyses

•* CHAPTER THIRD SYNTHESIS AND CHARACTERIZATION OF NEWLY CONDENSED COMPLEXES

PAGE NO.

1-37

38 52-57

53 54 54 55 55 56 57

58 -153

3.1 Synthesis and Spectoscopic Studies of Hetrobimetallic Complexes.

59

3.1.1 3.1.2 3.1.3 3.1.4

3.2

3.2.1 3.2.2 3.2.3 3.2.4

Introduction Materials and Methods Results and Discussion References

Synthesis and Characterization of Tetraxotetraamide Macrocyclic Complexes. Introduction Materials and Methods Results and Discussion References

59 60 62 78

80

80 81 83 97

PAGE NO.

3.3 Synthesis and Spectroscopic Studies 99 of Tetraiminetetraamide Macrocyclic Complexes.

3.3.1 Introduction 99 3.3.2 Materials and Methods 100 3.3.3 Results and Discussion 102 3.3.4 References 115

3.4 Synthesis and Characterization of 117 Bis(macrocyclic) Complexes.

117 119 119 133

3.5 Synthesis and Spectroscopic Studies 135 of Dithiadiaza Macrocyclic Complexes.

3.5.1 Introduction 135 3.5.2 Materials and Methods 136 3.5.3 Results and Discussion 138 3.5.4 References 151

3.4.1 3.4.2 3.4.3 3.4.4

Introduction Materials and Methods Results and Discussion References

»* CHAPTER FOURTH CONCLUSION 154-157

This chapter elucidates general introduction to the basic information related to the coordination complexes and the previous work done by eminent scholars.

Cfl

GENERAL INTRODUCTION

THVescr ib ing the full historical survey of coordination

J - ^ ^ chemistry which encompasses a great diversity of

substances and phenomena is beyond the limits of this chapter,

but it can be quoted that G.B.Kauffman1"5 has contributed to

this regard through his publications reviewing the pre-werner

theories and post-werner developments in a chronological order.

Although coordination chemistry comprises a large body of

current research in inorganic chemistry, it still presents

stimulating theoretical and practical challenges to an inorganic

chemist. The rapidly developing realm of bioinorganic chemistry is

Chapter 1 General Introduction CD

based on the presence of coordination compounds in living systems.

Many substances in vivo behave as multidentate ligands containing

numerous donor sites and act as metal carriers on complexation. For

example, many enzymes act as catalysts in the biological systems

which control the synthesis and degradation of biologically important

molecules and predominantly depend upon a metal ion for their

activity. Among the metals, molybdenum which achieved prominence

has attracted interest chiefly because of its role in biological

processes and also it shows a great variety of oxidation states and

coordination numbers. The newer types of compounds, mainly

coordination compounds, which have received vast study are

catalytically important (with their ease of oxidative addition and

reductive elimination), are the phthalocyanines, macrocycles, crown

ethers, metal-metal bonded complexes (metal clustures) and the

complexes in which hydrogen, ethylene, organic phosphines and

carbon monoxide behave as ligands. A highly comprehensive volume

has been devoted to the application of several coordination

compounds in various fields of practical importance to mankind.

The coordination complexes of a wide variety of Schiff-base

ligands have been extensively studied and reviewed8"14. The current

interest lies in the synthesis of multidentate ligands because of their

Chapter 1 General Introduction

ability to form mono and bis-species, yielding complexes with

different structural features. The metal derivatives of these ligands

have drawn substantial attention from the researchers for their

biological activities15"22. The molecules of life such as amino acids

have been exploited for the synthesis of Schiff-base ligands and their

23-32 transition metal complexes

The idea that two metal atoms in close proximity could react in

a cooperative manner with substrate molecules gave rise to binuclear

system . A major role in the building of binuclear complexes has

been played by tertiary diphosphines, bis(diphenylphosphino)

methane (dppm) being particulary efficient for this purpose .

Substitution of one of the donor atoms in the dppm skeleton for a

softer (As) or harder (N) centre has been introduced to create

heterobinuclear complexes of the platinum group metals3""39. Such

ligand systems studied by Balch have led to the synthesis of Pt-Rh

complexes having two bridging ligands A large number of

transition metal-gold multimetallic complexes have been prepared

containing transition metals V. Cr. W. Mn, Re, Fe, Ru. Os. Co, Rh,

Ir. Pt and Ag41"4\ On the other hand, the synthesis and

characterization of Pd-Au cluster compound has been reported

because Pd is a catalytically important metal and Au-Pd heterogenous

Chapter 1 General Introduction i CE

catalysts are known and commercially used for oxidation catalysis .

Copper(II) complexes with various ligands derived from oxalates,

oxamidates, oxamates [CuL] are known to act as paramagnetic

ligands towards other metal ions46 . In particular it has been found

that strong antiferromagnetic coupling is operative when CuL is

bound to metal ions (Cu"\ Ni2~ or Mn2T) in a pseudo-octahedral

(square-planar in case of copper) environment47"50. Kahn and co

workers 5 ' have found that CuL can form ferromagnetic chains with

XV and Mn" and that these chains can order magnetically at

sufficiently low temperature. F a b r e t t i " has used CuL as a

paramagnetic ligand which forms with nickel(II) a trinuclear

complex. The peculiarity of this compound is that the central

octahedrally coordinated nickel(II) ion has two water molecules with

c/A-configuration. In the recent past the crystal and molecular

structure of a very interesting binuclear compound, bis [|A-3, 5-bis(21

-pyridyl) pyrazolate- N1 X :X : X"]-bis [dimethanol nickel(II)]

dichloro -dihydrate has been reported54. Two methanol molecules

have been shown to be bonded to each nickel(II) rendering an

octahedral environment.

The chemistry of macrocyclic ligands proves to be a

challenging research area, as these molecules display unique and

Chapter 1 General Introduction |

exciting chemistries due to their function as receptors for substrates

of widely differing physical and chemical properties and upon

complexation can drastically alter these properties. The numerous

work done by countless researchers with thousands of papers,

hundreds of reviews and numerous patents about the chemistry of

macrocyclic complexes can not be confined to few pages. The field

has undergone spectacular growth after the early 1960s due to the

pioneering independent contributions of Curtis55 and Busch56.

The synthesis and applications of macrocyclic moieties

involving aza(N). oxa(O), phospha(P) and sulfa(S) ligating atoms

have been a subject of considerable interest in the recent years. The

designing of new macrocyclic complexes is a current domain of

research due to their use as models for protein metal binding sites of

metalloproteins in biological system"7"60, as therapeutic reagents in

chelate therapy61 '6", as cyclic antibiotics that owe their antibiotic

actions to specific metal complexation63 '65, as models to study the

magnetic exchange phenomena6 6 6 7 and in catalysis6869 . Besides

these, there are a number of important biological processes such as

photosynthesis and dioxygen transport70 in which macrocyclic

complexes are involved.

Chapter 1 General Introduction B

The first macrocyclic compound prepared from a diacid was

dimeric ethylene succinate [1] reported by Vorlander in

V—v° / 6 CK

Fig. 1

1894, subsequently, very little work was done with macrocyclic

diesters untill 1930's when Carothers and co-workers commenced

a study of polyesters including the macrocyclic monomeric and

dimeric carbonates, oxalates etc. The main interest in macrocyclic

diester compounds involved their use in preparation of perfumes

First documented macrocycle possesing a (Pynole) [2]

subheterocyclic ring was synthesized in 1886 by Baeyer 4 via the

condensation of pyrrole and acetone in the presence of mineral acid.

Macrocycles can be synthesized either by template method or

via non-template synthetic routes. The former route is prefered

because of the conformational requirements of the reacting species in

the reaction medium. The metal ion plays an important role in

Chapter 1 General Introduction

H,Cv o •CH,

N 0 H3C

N

CH,

Fig. 2

directing the steric course of the reaction and this effect has been

termed as "metal template effect"75. The exciting aspect of this effect

is that in majority of cases the molecules meet the design criteria

very well. The metal ion may also direct the condensation

preferentially to cyclic rather than polymeric products and there by

increasing the yield of product. The preparation of the free

macrocycle has certain advantages in many cases. Firstly purification

of the organic product may be more readily accomplished than

purification of its complexes and secondly, the characterization by

physical techniques will be more easy. However, the synthesis of a

macrocycle in the free form results in a low yield of the desired

product with side reactions, such as polymerization as predominating

effect. In order to overcome this problem, the ring closure step in the

synthesis may be carried out under conditions of high dilution76.

Chapter 1 General Introduction ] CXI

The multidentate macrocycles give rise to unique, rather cryptic

77 7ft

geometries ' These macrocyclic ligands are cyclic molecules

consisting of an organic framework interspersed with heteroatoms

which are capable of interacting with a variety of species. It is now

well established that macrocyclic molecules containing the biting

centres as [N4], [N6], [N8], [N 40 2] , [N4S2],and [N2S2] display unique

and exciting chemistry in that they can stabilize unusual higher

oxidation states of metal ions. The chemistry of metal complexes

with cyclam or related tetraaza macrocyclic ligands has been

extensively developed . These macrocyclic complexes have proven

to be a topic of continual and growing interest to coordination

chemists. Curt is has demonstrated the template potential of metal

ions in the formation of the isomeric tetraazamacrocyclic complexes

[3 and 4] by treating [Ni(en)3](C104)2 (Scheme 1) with acetone80.

The first example of a deliberate synthesis (Scheme 2) of a

macrocycle [5] using this procedure was described by Thompson and

Busch5 . Much of the early work featured the use of transition

metal ions in the template synthesis of quadridentate macrocycles:the

directional influence of orthogonal d-orbitals was regarded as

instrumental in guiding the synthetic pathway81 . This technique has

\3

H2 H 2

>U N \ /

H2 H 2

VrO

o re ft

O § • ' o

5' 3

Scheme 1. Illustration of the formation of macrocyclic complexes by the metal template method by Curtis.

H 2 N N S

w R^O

R. /"A N .S

\ / Ni

w r^

Br

Br

r\

Scheme 2. The first example of a delibrate synthesis of macrocycle by template method by Thompson and Busch.

Chapter 1 General Introduction an been extended in the last decade by using organotransition metal

derivatives to generate tridentate cyclononane complexes . The

synthesis of macrocyclic complexes by the metal template method

was extended by the use of .v,/?-block cations as template devices to

synthesize penta and hexadentate Schiff-base macrocycles " and a

range of tetraimine Schiff-base macrocyies by the Sheffield

j r» l r . ^ 0 . 9 1 ,

and Belfast research groups.

The template potential of a metal ion in the formation of a

macrocycle depends on the preference of the cations for stereo -

chemistries in which the bonding ^-orbitals are in orthogonal

arrangements. This is exemplified by the observation that neither

CuH nor Ni" act as template for the pentadentate "'1 + 1" macrocycles

[6-8] derived by the Schiff-base condensation of 2.6-

diacetylpyridine with triethyienetetraamine. N,N -bis(3-amino-

propyl) ethylenedia mine or N. N -bis(2-aminoethyl)-1.3-propane-

diamine.respectively. However. M g ' \ Mn" . Fe~\ Fe '". Co" . Zn" .

Cd2 and Hg2 serve as effective templates leading to the

formation of /-coordinate complexes of [6 and 7] and pentagonal

bipyramidal geometries for Mg "". Mn'". Fe '" , Fe^ . Zn2 . Cd" and

6-coordinate pentagonal pyramidal geometries for Co2 . Cd2 and

Hg" ** . The metal ion and the anion are important to the template

Chapter 1 General Introduction 13

Fig. 6 Fig. 7

Fig. 8

process because the balance between the size of the cation and

anion will determine the degree of dissociation of the metal salt in

the reaction medium47.

Chapter General Introduction 14

The formation of "1+1" macrocycle via intramolecular

mechanism or "2+2" macrocycle via the bimolecular mechanism

depends on one or more factors during the synthesis of Schiff-

base macrocycles. They are

1) The insufficient chain length to span the two carbonyl groups

in the diamine will block the formation98 of "1 + 1" macrocycle.

2) A "2+2" condensation may occur" if the template ion is

large with respect to the cavity size of the "1-^1" ring.

3) The electronic nature of the metal ion and the requirement of

a preffered geometry of the complex.

4) The conformation of the "1 + 1" acyclic chelate.

In the synthetic pathway of macrocycles the size of

cation used as the template has proved of much importance. The

compatibility between the radius of the templating cation and "hole"

of the macrocycle contributes to the effectiveness of the synthetic

pathway and to the geometry of the resulting complex. For example,

cations of radii less than - 0.80A0 do not seem to generate complexes

of [8]. Fenton and co-workers 8 S . 8 8 . 9 1 . 0 9 . J 0 0 d e m o n s t r a t e d c a t i o n .

cavity "best fit" in the formation of Schiff-base macrocycles by

synthesizing oxaazamacrocycles using alkaline earth cations as

templating devices. The smaller metal ion favours the formation of

Chapter 1 General Introduction QI

"1 + 1" [9] while the large metal ion favours the formation (Scheme 3)

of "2+2" macrocycle [10]. One of the alkaline earth cations, for

example, only magnesium generates the pentadentate "1 + 1"

macrocycle [9] but it is ineffective in generating the hexadentate

"1 + 1" macrocycle [11] which is readily synthesized in the presence

of large cations such as Ca2 , S r 2 \ Ba2 and pb2+. The preference

for the formation of "1 + 1"" or "2+2" Schiff-base macrocycle in the

metal template condensation depends on the cation radius. There is

an alternate method for the template synthesis of Schiff-base

macrocycle in which the metal free ligands can be synthesized by an

acid-catalysed condensation. Sessler et al.101 have produced pyrrole

containing macrocycles by the acid-catalysed Schiff-base

condensation of diformyltripyrrane with 1,2-diaminobenzene or 1.4-

diaminobutane. When the reaction was carried out in presence of

basic metal salts such as BaCO^ as a potential template, no

macrocycle could be isolated However, final product was obtained in

high yield when the Schiff-base condensation is effected in the

presence of stoichiometric quantities of larger cations such as CIO2"

and Pb~\ provided that an acid catalyst is also employed. The method

of synthesizing novel macrocycles by the acid-catalysed Schiff-base

condensation led to suggest a general "anion template effect".


+ H N 0 0 0 NH 2

S r 2 ; Pb2 '

r\ r-\ / H,N 0 i.' NH2

x—o /o —

Fig. 9

Fig. 11

N N ^

X

Fig. 10

Scheme 3


The Schiff-base condensation of the appropriate diamine and

dicarbonyl precursors in presence of an alkaline earth metal ion,

commonly resulted in the formation of macrocyclic complexes in

good yield87. Some reactions demonstrate the facility and

reversibility of amine exchange (transamination) and its importance

in the metal ion template synthesis of macrocyclic Schiff-base

ligands. Thus it has been observed that excess of free diamine or free

metal ion suppress the formation of macrocycle. The sequence of

reactions involving ring closure by transamination with a concomitant

ring contraction and reduction in ligand denticity and subsequent ring

expansion in the presence of larger metal ions is illustrated in

Scheme 4. Thus it has been described102 that when the metal ion is

too small for the macrocyclic cavity, ring contraction takes place by

transamination with a concomitant reduction in ligand denticity and

ring size. The complex of the ring contracted macrocycle undergoes

ring expansion in the presence of larger metal ions.

Lindoy and co-workers have developed design strategies for

new macrocyclic ligand systems which are able to recognize

particular transition and post-transition metal ions, they have

prepared ' " ? and studied the discrimination of metal ions by


+ r~\"/-\ -#v H2N N NH2 Ca, Ba

C * "D ^ N H

NH HN

2 H2N 3

Co2; Bo2* l s ^ J 2 Cu

2*

Scheme 4


r^ w W

Fig. 12 Fig. 13

ligand and by following the occurence of "structural dislocation"

along a series of closely related [12 and 13] mixed donor ligand

svstem 106-110

Macrocycles containig nitrogen donor atoms have been used as

models to explain metal ion-maci -cycle reactions in biological

systems. Among the poiyaza macrocycles, the tetraaza groups have

been the most extensively studied. Pentaaza and higher

polya7amacrocycles have begun to appear more frequently,

particularly in view of the potential of the larger macrocycles to bind

more than one matal ion. Margerum and co-workers 111-113 have

reported extensive investigations on the interaction of CM" and Ni"

with the macrocycles containing nitrogen donor atoms. The chemistry

of synthetic macrocyclic polyamines and macrocyclic

dioxopolyamines have been drawing much interest114""6. These

macrocycles form much more stable and selective complexes with

Chapter General Introduction W

various transition-metal ions than to open chain analogues having the

same donor arrangement. The metal complexes of the /-/-membered

cyclic tetraamine 1,4,8.1 1-tetraazacylotetradecane [14] represent

1 17 reference svstems in the coordination chemistry of

I I azamacrocyles. The synthesis of ligands [15 - 17] led to the

N N

H? NH

Fig. 14 Fig. 15

^ N H HN

Fig. 17 Fig. 16 J

U" study of their complexes. Studies on their complexes proved that

above [15 - 17] form stable complexes with transition-metal ions ' 1 9

and the Cu" complex of the /-/-membered [16] is the most stable among the three complexes . Majority of nitrogen-donor

macrocycles that have been studied are quadridentate e.g. ligands [14

and 18]. To fully encircle a first row transition-metal ion in a


macrocylic ring size of between 13 and 16 members are required

provided that the nitrogen donors are spaced such that, five, six- or

seven-membered chelate

coordination7 5 1 2 0 1 2 1 .

on rings are produced

A number of larger ring macrocycles

ft r\A/-\ W v w

Fig. 18 Fig. 19

containing more than four donor atoms have also been prepared and

one example of such a large ring ligand12" incorporating more than

one metal ion is shown in fig. 19. Roger Guiiard " and his

associates synthesized new cyclam-based macrobicyclic ligands.

Very recently acid catalyzed rearrangements between J,-/-dihydro-

2H-1, 5-benzooxazocine and benzothiazocine led to the formation of

/6-membered, 2-/-membered. 32-membered macrocyclic ligands 124

Chapter 1 General Introduction QI

Great efforts have been made in the incorporation of

functionalized pendant groups into a saturated macrocyclic structure

to modify conformational and redox properties of its metal

complexes. Recently E. Kimura and co-workers have exported a few

examples of the macrocycle dioxotetraamines bearing functionalized

pendant g roups 1 2 \ Hay and co-workers126 studied tetraaza system

which has pendant primary amine function able to coordinate the

metal centre. Bush and co-workers studied " a macrocycle with a

pendant pyridyl function which is sterically restricted in its binding

to the metal centres. Macrocyclic ligands with pendant donor groups

have received much attention in last few years ' " and in some

cases129 pendant donors have been found to stabilize the trivalent

oxidation state of nickel and destabilize the trivalent oxidation state

of copper.

The amide macrocyclic ligands are of great interest because

their metal complexes can function as porphyrin analogues in

catalyzing organic oxidation reactions1"1'1"". The coordination

chemistry of polyamide macrocycles is of particular interest in veiw

of two potential donor atoms i.e., amide nitogen and oxygen.

However in most of the polyamide macrocytic complexes, amide

nitrogen is engaged in coordination and not the oxygen133. The


formation of an amide is normally carried out after conversion of the

carboxyl component to a more reactive acyl derivative which can

react with the amino component under mild conditions. A number of

macrocyclic tetraamides have been described in the literature. Rybka

and Margerum134 have discussed the chemistry of ligand [20],

which was prepared by the conventional methods employed in

rf . H I I H

0 lCH2>m 0

H i u

/ \

Fig. 20 Fig. 21

peptide synthesis. An American group13" has described a general

method for the synthesis of macrocyclic tetraamide ligands [21] by

aminolysis of the thiazolidine-2-thione amides of dicarboxylic acids

with diamines. Macrocylic tetraamides can be prepared in high yield

bv this route.

Shakir et al. is currently engaged in the synthesis of amide

. They have reported a wide variety of macrocyclic complexes'36"140


/ M \ / M \ _

JIT N N X NN

O - ^ X v ^

H H rN N

CI H H N Nv

H H

0

M

/ | \ N CI

N N ' H H

^ 0

HN-' ^ / M C

N H\_

- X - .

iX

N

M:

N Ilk

Fig 22-26


tetraaza, hexaaza and polyaza macrocyclic [22-26] complexes

bearing amide groups. Most of them were prepared via the template

condensation reaction of (2+2) dicarboxylic acid with di or tri amines

and by self condensation of o-aminobenzoic acid. Very

recently 1 4 1 . 1 4 2 we were successful in synthesizing polyaza-

macrocyclic [27 and 28] complexes incorporated with peptide bonds.

Me

H II CI |„ N N | N N

Fig. 27 Fig. 28

Binucleating macrocyles were first obtained by Pilkington and

Robson *' by 2:2 condensation of 2.6-diformyl-4-methyl phenol and

1.3-diaminopropane The design and synthesis of binuclear

ma crocyclic transition metal complexes remains an important

Chapter 1 General Introduction 1 Q3

objective as potential catalysts due to influence of the two metal

centres on the electronic, magnetic and electrochemical properties of

such closely spaced paramagnetic centres. Binueleating ligands with

dissimilar coordination sites are of particular interest because such

macrocyclic complexes are thermodynamically stabilized and

kinetically retarded with regard to metal dissociation and metal

substitution relative to metal complexes of acyclic ligand.

Bis(macrocyclic) complexes incorporating two metal ions are of

great interest as they act as multi-electron redox agents or catalysts

and can be regarded as models for polynuclear metalloenzymes.

Furthermore they can exhibit interesting physical properties due to

the metal-metal interactions. Consequently, there has been a great

deal of work aimed at synthesizing biomimetic multinuclear models

which may provide insight into the actual structure of the

metalloenzyme or the mechanism of the catalysis. Recently

bis(macrocyclic) diiron and dinickel144 compounds have been

synthesized in which the diiron complex contains a conjugated bridge

between two metalin macrocyles. M.P. suh and co-workers14"

synthesized bis(macrocyclic) Ni(II) and Ni(l) complexes [29] by

template condensation reaction of formaldehyde and primary-


r\» \ N H

N — R — N JO

Fig. 29

diamines. Fenton has reviewed146 this class of compounds

emphasizing their relevances to bioinorganic model system. Some

polyaza macrocyclic complexes have been modified and the reactions

of nickel(II) and iron(II) complexes of 1.4,8,11-

tetraazacyclotetradecane [14] with H 2 0 2 and 0 2 respectively,

H / \ •N N

•N N = H \ /

H N N

N N H

were reported 1 4 7 . 1 4 8

Fig. 30

to produce correspoding complexes of

unsaturated [30] bis(macrocyclic) ligands. Shakir and co-

149 workers synthesized a new series of bis(macrocyclic)

complexes [31] from the template reaction of primary diamines.


vYvH H O M S s N / i N H

Fig. 31

formaldehyde and benzidine followed by the addition of diketones or

phthalaldehyde.

P. Comba and co-workers have also synthesized130 some bis-

(macrocyclic) octaamine dicopper(II) complexes in which they have

found that these dicopper(II) complexes do not exihibit any coupling

in their EPR spectra irrespective of the size of the bridge which is in

contrast to observation with other (CH2):-linked bis(macrocyclic)

dicopper(II) complexes1"1 1?2.

Metal-ion recognition is a fundamental property of many

processes in nature, but the factors influencing such recognition are

often not well understood, especially when substrates incorporating

mixed donor sets are present. The aza-crowns have complexation

Chapter I General Introduction ] Q3

properties that are intermediate between those of all oxygen crowns

and of all nitrogen cyclams. Recent153 studies have proved that

macrocylic thioethers readily bind to transition metal ions to form

stable complexes. Bernardo and co-workers'54 have made a study of

the influence of saturated nitrogen and sulfur donor atoms on the

properties of copper(II/I) macrocyclic polyamino polythiaether ligand

complexes. Many macrocyclic complexes in which the furanyl moiety

is part of the macrocyclic frame-work have been reponed

ear l ier l 5 V l ' 6 . Busch and co-workers7 5 1 2 0 1 5 7 have synthesized several

sulfur-nitrogen containing macrocydes by in situ methods in

presence of metal ions, yielding the metal complex directly.

Metal complexes mainly of nickel(II) and cobalt(II) containing

'wo sulfur and two nitrogen1"8"160, four sulphur and four nitrogen1 ',

two sulfur, four nitrogen and one sulfur and four nitrogen

donors (,~ have been synthesized and in some cases the metal-free

ligand has also been obtained. The complexes with four sulfur and

two nitrogen donors have four sulfur atoms in an equitorial plane and

two nitrogen atoms are at trans positions. However, in two sulfur and

four nitrogen donor atom complexes, the metal is located in a cavity

bound by six donor atoms octahedrally. Funkemeier and


Fig. 32

163 co-workers recently. reported the synthesis of /-/-membered

trans N2S2 dibenzo macrocycle [32]. Very recently, J. Scowen with

other researchers164 reported metal-ion directed synthesis of

novel sufur-based [33 and 34] macrocycles. Reaction forming acid-

stable dittiiadiaza macrocycles proceeded in reasonable yield with

1 *

\

-Xi •W

oc * s

s

N

Fig. 33 Fig. 34

Chapter 1 General Introduction ] QE

carbon acid, even when stoichiometric amount of the carbon was

employed. Evidently, the condensation reaction of forming 13 to 16-

membered macrocycles for N4 donor molecules165"166 transfers readily

to mixed S2N2 donor analogues, with the presence of a pair of cis

disposed primary amine groups being the primary requirment for

condensation.

In recent years1 6 7 1 6 8 considerable attention has been devoted

for the synthesis and characterization of mixed nitrogen, oxygen and

sulfur donor atom macrocyles. L.F.Lindoy and associates

synthesized novel macrocyclic ring [35] incorporating mixed

NH 1

Fig. 35

(O4N2. O2S2N2 and N2S4) donor set and its complexation behaviour

towards copper(II), silver(I) and Lead(II) was also studied. The

behaviour towards silver(I) was of particular interest since inherent

in the design of these systems are structural features which appeared

•9 i>

Chapter 1 General Introduction ] EH

likely to enhance their relative affinity for this ion over other ions of

interest.

The synthesis of novel polythioether macrocyclic ligands and

their studies of coordinating abilities towards transition metal ions

have come into great prominence in last years. In spite of the fact

that the thioethers were formerly considered poor donors to the

transition metal ions1 °. Extensive work has been reported171, mainly

because of their possible use as models for metalloproteins. L.

1 7 ^

Escriche and his associates ' reported the synthesis of a large

macrocycle incorporating six sulfur atoms into the macrocyclic

frame-work and its structure was determined on the basis of x-ray

crystallography. Therefore, a great quantity of chemical and

structural information regarding their complexes may now be found

in the literature.

The observation that transition metal Schiff-base complex

[ML](L = quadridentate Schiff-base) can function as a neutral donor

ligand has led to several investigations of their reaction with tin

Lewis acids and to the isolation of their adducts174 175. In recent years

considerable spectroscopic information has been obtained on the

transition metal-tin complexes176. This not only has provided

additional insight as to the structures of these complexes and the


nature of transition metal-tin bonding, but also has given detailed

information as to the nature and relative amounts of the various

species present in solution. There is emerging greater use of these

species in the catalysis of organic transformations, such as def ine

hydrogenation and isomerization, reductions under water gas shift

conditions, hydroformylations coupling reaction among others.

The coordination chemistry of stannylenes, R^Sn explains a

considerable amount concerning tin-transition metal complexes.

These compounds use two of their p electrons in covalent bonding

and their other two electrons constitute a lone pair that can be used

to form an adduct with a lewis acid. There are also low-lying empty

p and d orbitals, which when used in the hybridization of the orbitals

of tin. create empty orbitals suitable for complex formation. There

sp

I

/ ••Sn— :Sn

sp

i i

:Sn \

sp

i l l

:Sn "Sn

s p 3 d

IV

sp J d '

Fig. 36

are several hybridization geometries177 available [36] for stannylenes.

Chapter 1 General Introduction 1 Ql

The first and fifth structures are uncommon for tin in transition metal

chemistry1 7 7 1 7 8 , while the second, third and fourth are most

important. Stannylenes form stable adducts with hard Lewis bases

such as amines and ethers, soft Lewis bases like halides, hard Lewis

acids1 7 y l 8° like the boron halides and soft Lewis acids like transition

. i 1 7 7 . 1 8 !

metals

The ability of metal salicylaldimine complexes to act as

effective bidentate donor ligands to tin(IV) halides, organo-tin(IV)

halides, pseudohalides and tin(II) halides are well

documented174 1 8 2 1 8 \ B.Clarke and co-workers recently reported184

the crystallographic and tin-119 mossbauer spectroscopic studies of

heterobimetallic complexes of 3-methoxysalicylaldimine ligands.

Many research groups have shown that tin(IV) Lewis acids form 1:1 i n i | i r I R S

adducts with transition metal Schiff-base complexes " and the 1 S f\

structures of many such adducts have been reported . One of the

specific interest in complexes of this type relates to the manner in

which the dioxygen-carrying properties of cobalt salicylaldimine

complexes are altered when they assume the role of donor Uganda,

particularly to t i n 1 8 . Siddiqi and his associates

synthesized188 heterobimetallic complexes of the type

[Cu(TETA)Cl2SnCl2] and [Cu(TETA)Cl2SnPh2] by treating

General Introduction

EtOH

H

r K / ^ H i

Cu

/ L MH,

\r

H + 2HCI \

"V

/ L

Cu Sn

N -A.

VS

C6»5

CI

Scheme 5

Chapter General Introduction f36l

[Cu(TETA)Cl2] (TETA = triethylenetetraamine) with SnCl4 (Scheme

5). Interestingly the interaction of [Cu(TETA)Cl2 SnCl2] with an

exces of KBH4 in THF leads to the formation189 [37] of

[Cu(TETA)(BH4)2Sn(BH4]2. The complexes [38] of

CI

— N

•N

\ I

l\

N

Cu

N

J H

CI

s

Fig. 37 Fig. 38

[Cu(TETA)Cl2 M(TMDTC)2] (M = Si, Ge, Sn, Ti and Zr; TMDTC =

tetramethylene-dithiocarbamate) also appeared in the literature

Metal complexes of tetradentate Schiff-bases can act as bidentate

ligands coordinating to both transition and alkaline earth metal

atoms . I t has been shown that organo-tin(IV)chlorides form

molecular complexes with tetradentate Schiff-bases as well as with

their metal complexes. The bahaviour of bidentate ligand, N, N'-


ethylene bis(Salicylideneiminato) nickel(ll) towards organo-

tin(lV)chlorides resulted in the formation of heterobimetallic adduct

and its structure has been studied through crytallographic studies 192

Cunningham and co-workers have made many spectroscopic

studies187 especially mossbauer investigation of the transition metal

Schiff-base complexes as ligands in tin chemistry. The interesting

chemical and stuctural consequence of replacing one chloride by a

1 8 S

hydroxide or alkoxide ion have also been attempted ".

The chemisty of transition metal-tin and macrocyclic complexes

is an expanding field of research and thus thought worthwhile to

carry out some synthesis of novel heterobimetallic and marocyclic

moieties which may add up to this vast area of knowledge.

Chapter 1 | [ References j | 38

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I Chapter References 40

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Chapter 1 References i an

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CHAPTER-This chapter covers the basic instruments used for characterizing the various complexes.

Chapter 2 Instruments Used | | 53

INSTRUMENTS USED

2.1 IR SPECTROSCOPY

T •he IR spectra (4000-200 cm"1) were recorded as

KBr discs on an IR 408 Shimadzu

spectrophotometer. Some of the important group

frequencies in the IR spectra pertinent to the discussion of

the newly synthesized compounds are:

(i) N-H stretching frequency

(ii) C-N stretching frequency

(iii) C=N stretching frequency

Chapter 2 Instruments Used 54

(iv) Sn-N stretching frequency

(v) M-N stretching frequency

(vi) M-0 stretching frequency

(vii) M-Cl stretching frequency

(viii) M-S stretching frequency

(ix) Amide bands

2.2 *H NMR SPECTROSCOPY

'H NMR spectra in d6 -DMSO using a Bruker AC 200 E and

Bruker FX -100 FT nuclear magnetic resonance spectrometer with

Me4Si as an internal standard were obtained from GNDU, Amritsar

and IIT, New Delhi, India. All the samples were recorded at room

temperature (22-24 °C). All the factors connected with the recording

of the spectra were taken care off. The frerquency used was around

200 MHz.

2.3 EPR SPECTROSCOPY

EPR spectra of all the copper complexes were recorded on a

Jeol JES RE2X EPR spectrometer at room temperature from the

Physics Department, Aligarh Muslim University. Aligarh, India. The

gll , gi and G values were calculated from these spectra.

Chapter 2 Instruments Used QE

2.4 UV - VIS. SPECTROSCOPY

Electronic spectra (10*3 M solution) in DMSO were recorded on

a Pye-Unicam 8800 (Philips, Holland) UV-vis. spectrophotometer at

room temperature from the Instrumentation centre, Aligarh Muslim

University, Aligarh. India.

2.5 MAGNETIC SUSCEPTIBILITY MEASUREMENTS

Magnetic susceptibility measurements were determined at

25°C using a Faraday balance calibrated with Hg[Co(NCS)4] . When

magnetic susceptibility is considered on the weight basis, the gram

susceptibility (xg) is used instead of volume susceptibility. The u.eff

value was calculated from the gram susceptibility multiplied by the

molecular weight and corrected for diamagnetic values as

^ e f f = 2 - 8 4 V X M C , " T . B.M.

Where T is the absolute temperature at which the

experiment is performed. The gram susceptibility is measured by the

formula

_ AW W s t d

W AWstd


where

AW

W

Wstd

^s td

Gram susceptibility

Change in weight of the unknown sample with magnet

on and off.

Weight of the known sample.

AWstd = Change in weight of standard sample with magnet on

and off.

Weight of standard sample.

Gram susceptibility of the standard sample.

2.6 MOLAR CONDUCTANCE MEASUREMENTS

Electrical conductivity data 10" M solutions in DMSO were

obtained with a Systronic type 302 conductivity bridge thermostated

at 25 ± 0 . 1 °C. The molar conductance (Am) which is related to the

conductance value is calculated by

Cell constant x Conductance Ar

Concentration of solute expressed in mol cm"3


2.7 ELEMENTAL ANALYSES

The results of elemental analyses for carbon, hydrogen and

nitrogen were carried out with a Thomas and Coleman analyser,

Carlo Erba 1108 from CDRI, Lucknow, India. Metals and Chloride

were determined volumetrically and gravimetrically, respectively by

standard methods. For the metal estimation a known amount of

complex was decomposed with mixture of nitric, perchloric and

sulphuric acids in a beaker. It was then dissolved in water and made

upto a known volume followed by volumetric titration with standard

EDTA. For Chloride estimation a known amount of the sample was

decomposed in a platinum crucible and dissolved in water with a

little concentrated nitric acid. The solution was then treated with

silver nitrate solution. The precipitate was dried and weighed.

CHAPTER-3 This chapter deals Mith the basic experimental procedures, reagents used to perform the synthesis of various complexes and their results and discussion.

Chapter 3 Heterobimetallic Complexes 59

3.1

SYNTHESIS AND SPECTROSCOPIC STUDIES OF HETEROBIMETALLIC COMPLEXES

3.1.1 INTRODUCTION

There are a variety of synthetic methods available for the

formation of transition metal-tin bonds and several excellent

reviews' 4 have appeared on the studies of transition metal-tin

complexes during the past few years. The complexation behaviour of

tetradentate transition metal chelates to act as effective bidentate

donor ligands to tin(IV) halides, organotin(IV) halides and

pseudohalides are well investigated5"9. One of the specific interest in

1:1 adducts of tin-transition metal Schiff-base complexes lies with


the fact that the dioxygen carrying properties of transition metal

Schiff-base complexes are altered when act as donor ligands to tin .

This part of the chapter describes synthesis of a new series of tin-

transition metal complexes with a view to study the ligating

behaviour of the tetradentate ligands towards transition metal and

non-transition metal ions simultaneously.

3.1.2 MATERIALS AND METHODS

The metal salts, NiCl2 .6H20, CoCl2 .6H20, MnCl2 .4H20,

CuCl 2 .2H 20 and ZnCl2 were of BDH quality. Benzil. 1-2-

diaminoethane, 1,3-diaminopropane, 2,4-pentanedione and tin(IV)

tetrachloride (all E.Merck) were used as received. The solvents,

methanol and dimethylsulphoxide were commercially available pure

samples and were dried before use.

Dichloro(l,2-diphenylethane-l,2-dione bis 1,2-diamino-

ethane)metal(II)-dichlorotin(IV),[MCI2L1SnCl2]; dichloro (1,2-

diphenylethane-1,2-dione bis l,3-diaminopropane)metal(II)-

dichlorotin(IV), [MCI2L2SnCl2] [M = Mn", Co", Ni", Cu11 and

Zn"j.

Chapter 3 Heterobimetallic Complexes ] EH

A mixture of 1,2-diaminoethane or 1,3-diaminopropane (0.67,

0.74 cm ,10 mmol) and benzil (1.05 gm, 5 mmol) in methanol (50

cm ) was taken in a round bottomed flask and stirred with gentle

heating for about 15 min. Then a hot methanolic solution (50 cm ) of

metal(II) chloride (5 mmol) was added followed by the addition of

tin(IV) chloride (1.3 gm. 5 mmol) in methanol (50 cm3). The addition

of tin(IV) chloride showed a gradual change in colour of the solution

either into more light colour or into a new colour. The final mixture

was stirred for another 7 hrs. and the resultant product thus obtained

was filtered, washed several times with methanol and dried in vacuo.

Dichloro(l,3-dimethylpropane-l,3- dione bis 1,2-diamino-

ethane)metal(II)-dichlorotin(IY), |MCl2L3SnCl2]; dichloro(l ,3-

dimethyl-propane-l,3-dione bis l,3-diaminopropane)metal(II)-

dichlorotin(IV), [MCl2L4SnCI2]lM = Mn", Co", Ni", Cu" and

Zn11].

These compounds have been prepared by adopting the same

procedure as described above. Here instead of benzil the diketone

2,4-pentanedione (0.51 cm3. 5 mmol) was employed for the

condensation of the amine moiety, but the addition of tin(lV)

chloride showed a sudden change in colour of the solution.


3.1.3 RESULTS AND DISCUSSION

The reaction of 1,2-diaminoethane or 1,3-dia-

minopropane, with diketones (benziL 2,4-pentanedione) in presence

of transition metal salts and tin(lV) chloride in 2:1:1:1 molar ratio

gave a new series of heterobimetallic complexes exhibiting the

stoichiometry [MCl2LSnCl2] [M = Mn", Co", Ni", Cu11 and Zn11; L

= L! - L4] as shown in Scheme 6. All the complexes are stable to

atmosphere at room temperature. These adducts have very low

solubility in organic solvents but are freely soluble in polar solvents

such as dimethylformamide, dimethylsulphoxide and acetonitrile. All

the complexes were found to give higher yields (53-68%). The

elemental analyses (Table 1) results are acceptable with the proposed

stoichiometry of the adducts. The molar conductance values in

dimethylsulphoxide (DMSO) measured for all the compounds are

found to be low and are consistent11 with the non-electrolytic nature

of these compounds.

The prominent IR spectral results of the compounds are given

in the Table 2. The main feature of the IR spectra is the appearance

of a band around 1600 cm'1 which can be unambiguously assigned to

the azomethine linkage v(C=N) and is consistent12 with coordinated

imine bonds. This information along with the absence

Chapter Heterobimetallic Complexes ] [

z 5

?• r,— z- 5

I A / •z z .

H

X. x a.

A/X x o * o x

c

c

\ / c in

*£ ^

S ^ * ° x

/ \ z z

M x CL a.

\ /

c

.A . C \ ~\ -> £"c * a o x

v/ \y

c

•9 C C!

""3

o U

<s f } «s f» -II II II II -

= = = = II »- •* r- »•

J J J J S

Table 1. % yield, Colour, Melting point, Molar Conductance and Analytical Data for the Compounds.

Found (Calc.)% Compound % Yield Colour Melting Am

Point (cm ft mol ) c H N M Cl Sn

TO

[MnCl 2 L 1 SnCl 2 ] 65 Moon m i s t 300 1 9 . 7 3 9 . 8 4 . 2 1 0 . 7 1 0 . 2 1 3 . 5 2 1 . 7 ( 4 0 . 2 ) ( 3 . 7 ) ( 1 0 . 4 ) ( 1 0 . 2 ) ( 1 3 . 2 ) ( 2 2 . 1 )

[MnCl 2 L 2 SnCl 2 ] 63 G r e y s t o n e 2 4 1 - 2 4 3 1 4 . 5 4 3 . 0 4 . 5 1 0 . 3 9 . 5 1 3 . 0 2 0 . 6 ( 4 2 . 5 ) ( 4 . 3 ) ( 9 . 9 ) ( 9 . 7 ) ( 1 2 . 5 ) ( 2 1 . 0 )

[MnCl 2 L 3 SnCl 2 ] 65 Cream 263 1 9 . 5 2 4 . 9 4 . 2 1 3 . 6 1 3 . 3 1 7 . 0 2 8 . 1 ( 2 5 . 3 ) ( 4 . 3 ) ( 1 3 . 1 ) ( 1 2 . 9 ) ( 1 6 . 6 ) ( 2 7 . 8 )

[MnCl 2 L 4 SnCl 2 ] 62 C o l o u r l e s s 2 6 1 1 6 . 1 2 9 . 5 4 . 5 1 1 . 9 1 1 . 8 1 5 . 9 2 5 . 8 ( 2 9 . 0 ) ( 4 . 9 ) ( 1 2 . 3 ) ( 1 2 . 1 ) ( 1 5 . 6 ) ( 2 6 . 1 )

[ C o C l 2 L J S n C l 2 ] 68 Dim b u r n o u s 252 2 4 . 6 4 0 . 2 4 . 0 1 0 . 1 1 1 . 1 1 2 . 8 2 2 . 1 ( 4 0 . 0 ) ( 3 . 7 ) ( 1 0 . 4 ) ( 1 0 . 9 ) ( 1 3 . 1 ) ( 2 2 . 9 )

[CoCl2L2SnCl2] 67 Lead grebe 231 18.6 42.7 4.1 10.3 10.7 12.3 21.3

(42.2) (4.2) (9.8) (10.3) (12.4) (20.8)

[CoCl2L3SnCl2] 68 Sonore 253 15.5 24.8 4.4 12.7 14.3 17.0 28.1

(25.1) (4.2) (13.0) (13.7) (16.5) (27.6)

[CoCl2L SnCl2] 65 Sponge >340

[NiCl2L1SnCl2] 57 Light green 160 19

[NiCl2L\SnCl2] 54 Light green 258

[NiCl2L SnCl2] 57 Light green 23! 17

[NiCl2L SnCl2] 53 Light green 25! 12

[CuC]2L SnCl2] 59 Sky blue 2 62

[CuCl2L SnCl2] 61 . Aqua green 219 12

[CuCl2L SnCl2] 59 Sky blue 267 10

29.3 5.1 11.8 (28.8) (4.8) (12.2)

40.4 3.8 10.2 (40.0) (3.7) (10.4)

41.8 4.0 10.3 (42.2) (4.2) (9.8)

24.8 4.5 12.5 (2 5.1) (4.2) (13.0)

29.1 4.6 11.8 t28.8) (4.4) (12.2)

40.1 3.5 10.0 (39.6) (3.7) (10.3)

42.0 4.5 10.1 (41.9) (4.2) (9.8)

25.0 4.3 13.2 (24.8) (4.2) (12.9)

13.2 15.5 26. 1 (12.8) (15.4) (25.9)

10.3 12.7 22.3 (10.8) (13.1) (21.9)

9.8 12.8 21.3 (10.3) (12.5) (20.9)

14.0 16.9 27.3 (13.6) (16.5) (27.6)

13.1 15.3 25.4 (12.8) (15.5) (25.9)

12.0 13.3 22.1 (11.6) (13.0) (21.7)

10.6 12.8 20.3 (11.1) (12.4) (20.7)

14.8 15.9 28.0 (14.6) (16.3) (27.5)

[CuCl 2 L 4 SnCl 2 ] 56 O c e a n g r e y 266 1 1 . 4

[ Z n C l 2 L 1 S n C l 2 ] 64 O f f - w h i t e 220 1 0 . 4

[ Z n C l 2 L 2 S n C l 2 ] 62 C o l o u r l e s s >340 7 . 6

[ Z n C l 2 J J3 S n C l 2 ] 65 O f f - w h i t e 2 4 9 2 2 . 0

[ZnCl 2 L S n C l 2 ] 60 O f f - w h i t e 320 2 1 . 0

2 8 . 0 5 . 1 1 1 . 8 ( 2 8 . 5 ) ( 4 . 8 ) ( 1 2 . 1 )

3 9 . 0 3 . 3 1 0 . 5 ( 3 9 . 5 ) ( 3 . 7 ) ( 1 0 . 2 )

4 2 . 1 4 . 4 1 0 . 2 ( 4 1 . 7 ) ( 4 . 2 ) ( 9 . 7 )

2 5 . 0 4 . 5 1 3 . 1 ( 2 4 . 7 ) ( 4 . 1 ) ( 1 2 . 8 )

2 8 . 3 4 . 5 1 1 . 8 ( 2 8 . 4 ) ( 4 . 8 ) ( 1 2 . 0 )

1 4 . 1 1 5 . 6 2 6 . 0 ( 1 3 . 7 ) ( 1 5 . 3 ) ( 2 5 . 6 )

1 2 . 0 1 3 . 1 2 2 . 2 ( l l . ' M ( 1 2 . 9 ) ( 2 1 . 7 )

1 1 . 7 1 1 . 9 2 1 . 0 ( 1 1 . 4 ) ( 1 2 . 3 ) ( 2 0 . 6 )

1 5 . 1 1 5 . 7 2 6 . 8 ( 1 4 . 9 ) ( 1 6 . 2 ) ( 2 7 . 1 )

1 3 . 8 1 4 . 8 2 6 . 1 ( 1 4 . 1 ) ( 1 5 . 2 ) ( 2 5 . 5 )

Table 2 . IR S p e c t r a l Da ta (cm ) f o r t h e Compounds.

Compound v(N-H) V(C-H)

[MnCl2L1SnCl2] 3150 2915

[MnCl;>L2SnCJ2] 3165 2 900

[MnCl2L3SnCl2] 3170 2890

[MnCl2L4SnCl2] 3155 2910

[CoCl2L1SnCl2] 3175 2940

[CoCl2L2SnCl2] 3180 2900

[CoCl2L3SnCl2] 3190 2930

[CoCl2L4SnCl2] 3160 2880

V(C=N) V(C-N) v(Sn-N) V(Sn-Cl

1610 1135 380 32C

1600 1120 360 300

1605 1125 390 340

1600 1130 375 360

1610 1120 380 330

1605 1140 365 350

1605 1130 370 335

1600 1135 380 360

) V(M-C1) V(M-N) Ring vibrations

270 440 1430,1090,730

280 450 1445,1085,745

275 465 -

265 435 -

260 455 1425,1085,740

280 450 1440,1060,735

260 460 -

280 450 -

[NiCl2L SnCl2]

[NiCl2L2SnCl2]

tNiCl2L3SnCl2]

[NiCl2L4SnCl2]

[CuCl2L1SnCl2]

[CuCl2L2SnCl2]

[CuCl2L3SnCl2]

[CuCl2L4SnCl2]

[ZnCl2LiSnCl2]

3170 2910

3185 2890

3165 2880

3180 2900

3160 2900

3180 2910

3190 2905

3175 2895

3170 2910

1610 1125

1600 1120

1595 1135

1605 1125

1610 1120

1615 1130

1600 1120

1605 1125

1600 1130

360 350

370 355

3 8 5 3 4 0

375 335

380 320

390 310

375 350

380 315

390 310

275 455

260 440

270 425

280 4 50

260 440

290 460

280 445

260 435

285 455

1410,1055,740

1430,1045,750

1435,1060,765

1420,1075,750

1450,1070,735

[ZnCl2L SnCl2] 3155 2890 1610 1135 365 320 255 440 14 60,1065,730

[ZnCl2L3SnCl2] 3165 2920 1615 1140 390 300 265 265 -

[ZnCl2L4SnCl2] 3180 2925 1595 1125 380 330 280 445 -

Table 3. H NMR Spectral Data* for the Compounds

Compound N-CH2-C C-CH2-C C-CH3-C=N C-NH-Sn N-C6H5-C=N

[ZnCl2L1SnCl2] 3.18(m) - - 6.08(m) 7.47(m)

[ZnCl2L2SnCl2] 3.21 (m) 2.03 (m) - 6.12 (m) 7.52 (m)

[ZnCl2L3SnCl2] 3.19(m) - 2.38(s) 6.14(m)

[ZnCl2L4SnCl2] 3.20(m) 2.11(m) 2.43(s) 6.20(m)

rChemical shifts (5/ppm) with multiplicities in parenthesis S = singlet and m = multiplet

Table 4. fieff Values, Ligand Field Bands observed in the Electronic Spectra (cm1) , their Assignments and EPR Spectral

Parameters for the Compounds.

Compound

[MnCl2L'SnCI2]

[MnCl2L2SnCl2]

[MnCI2L3SnCI2]

[MnCl2L4SnCI2]

^efT.

(B.M.)

5.79

5.77

5.80

5.77

Band position

(cm" )

18600

22100

18900

21500

18550

21900

19100

21300

Assignments EPR data

*M

6 A A l g

6A A i g

T ,g(p) 4T2g(F)

JA,g -+ 4T]g(P)

Llg

klg

6 A

A|g klg

T 2 g ( F )

> «T,g(P)

-» 4T2g(F)

T .g ( p )

[CoChL'SnCh] 4 54 13700

21500

[CoCl2L2SnCl2] 456 13500

21800

[CoCl2L3SnCl2] 4 57 13900

21400

[CoCl2L4SnCl2] 458 14250

21800

[NiCI^ 'SnCb] 3.14 11500

17900

[NiCl2L2SnCl2] 3.15 11600

17700

[NiCl2L-SnCl2] 3.15 11300

17500

4T,g(F) -> 4T |g(F) >

4T |g(F) -> 4T,g(F) - •

4T]g(F) -4T)g(F) -*

4T,g(F) -4 T , g ( F ) ^

' ^ g -> ?A2g ->

A2g -> V2g -»

\ g "»•

\ g -+

4A2g(F) -4T |g(P)

4A2g(F) -4T lg(P)

4A2g(F) -4T lg(P)

4A2g(F) -4T,g(P)

•T,g(F) -

'T,g(P)

V,g(F) -3T,g(P)

3T,g(P)

v© — O

ir, 00 r--

o T 00

o o 00 (N

o

rr 00

u. a. ^ o ^ o *D

SO (N UJ CQ sj rsi

SO

w r~i

oo rsi

CQ I N

ao 50 fN UJ CQ

r>i rvi

00 oo 7i

UJ CQ IN (N

00

< QO 00 00

< CQ CQ

^v * V p, ^^ ^K ^^

00 00 oo oo CQ CQ CO CQ

<N (N

00 00

CQ CQ

o o r-—

^ o cv

r»

o o r-oo

o o 00 I/",

o o •sD 00

o o (N o

o o —. <?•

o o f<"l vO

o © a 00

o o T \£>

00 ON o 00

o 00

c 00

u c

oo J

rv l

o 3 U^

u c oo

r- i -J

rsj

u 3

u

u c oo

r*". J

<N

u 3 V

u c 00

TJ-J

<N

u 3

u

Chapter 3 Heterobimetallic Complexes | | 74

of bands due to carbonyl groups strongly support that the

condensation of primary amine with the carbonyl groups has taken

place. Another important single band appeared around 3170 cm"

assignable to the v(N-H) of amino group. This band shows a marked

negative shift13 in all the complexes indicating coordination through

amino nitrogen. The appearance of band around 1125 cm" for all

the complexes may be attributed to v(C-N) vibration. The

appearance of a sharp band around 450 cm"1 is attributable14 to v(M

N) vibration. All of the tin(IV) chloride adducts exhibit a broad

intense band in the 300-360 cm'1 region which may probably be

associated with the v(Sn-Cl) frequencies. In the 750-900 cm'1 region

of the spectra, there are absorption bands which should arise from

methylene and methyl rocking vibrations together with symmetric C

N streching. A weak intensity absorption band in all the complexes

identified around 380 cm"1 probably be due to v(Sn-N) vibration \

The other fundamental vibrations appeared at their expected

positions.

The 'H NMR spectra (Table 3) of [ZnCl2LSnCl2] adducts

appear to be more complex and do not show any bands assignable to

primary amino protons. All the compounds gave two multiplets

between 6.08 and 6.20 ppm, and between 3.18 and 3.21 ppm which

Chapter 3 Heterobimetallic Complexes ] d

can be assigned16 '17 to the N-H protons (C-NH,2H) and the methylene

(CH2-N, 8H) protons of amine moiety, respectively. The spectra of

[ZnCl2L2SnCl2] and [ZnCl2L4SnCl2] showed a multiplet at 2.03 and

1 7

2.11 ppm, respectively which may be ascribed to the central

methylene (C-CH2-C,4H) protons of 1,3-diaminopropane portion.

However, the broadness of the 2.38 ppm band for the complex

[ZnCl2L SnCl2] may be due to the overlapping of middle methylene

protons of 2,4-pentanedione and 1,3-diaminopropane. A multiplet

appeared for the complexes [ZnCl2L'SnCl2] and [ZnCl2L2SnCl2] at

7.47 and 7.52 ppm and a sharp singlet observed for the complexes

[ZnCl2L3SnCl2] and [ZnCl2L4SnCl2] at 2.38 and 2.43 ppm may

correspond18 to the phenyl ring protons (C-C6H5,10H] and imine

methyl protons (CH3-C=N,6H), respectively.

The powder sample EPR spectra (Table 4) of [CuCl2LSnCl2]

have been recorded at room temperature which showed a single broad

signal with two g values. The absence of hyperfine splitting in these

complexes indicate that the paramagnetic centres are not diluted. It

has been reported that the values gj and gx have been used to

distinguish unambiguously19 between dx2_v, and the dz2 ground states.

For example, for the dx2_vJ ground state the EPR spectrum should give

8 | > gx and v i c e versa for d , ground state. The heterobimetallic

Chapter 3 Heterobimetallic Complexes | | 76

complexes exhibit g | and g± values in the range 2.23 - 2.28 and 2.10 -

2.14, respectively, which suggest an axially distorted octahedral

structure of copper(II) complexes where the unpaired electron is

present in the d , , orbital with 2B, as a ground state term. It should r x . . y 3 i g o

be noted that for an ionic environment gj > 2.3, while for covalent

environment gy < 2.3. The existance of gj values below 2.3 range

suggest the considerable covalent character of these complexes. The

axial symmetry parameter, G is obtained by the relation (g.,-2)/(gx-2),

which measures the exchange interaction between copper centres in

the crystalline solids. If G > 4 the exhange interaction is negligible

and if G < 4 the exhange interaction is considerable. In these

complexes the G values appeared in the range 1.785-2.800

indicating'1 the possibility of considerable exchange interaction.

The electronic spectra (Table 4) of all heterobimetallic

complexes [MnCl2 LSnCl2] exhibit two bands around 18600 and

22100 cm"1 regions corresponding to the 6 A ] g -> 4 T l g (P) and

A i g ""* ^2g(F) transitions, respectivelty, indicating an octahedral

geometry of manganese(II) complexes. Two ligand field bands for the

cobalt complexes in the 13500 - 14250 and 21400 - 21800 cm"1 may

be assigned to the 4 T l g ( F ) -> 4A2 g(F) and 4T, g (F) -> 4 T l g (P)

Chapter 3 Heterobimetallic Complexes i an

transitions, respectivety corresponding to the octahedral geometry

around cobalt. The nickel(II) complexes gave two distinct bands

around 11600 and 17700 cm"1 ascribed to 3A2g - • 3T,g(F) and

A2g ~* 3 ^ i g ^ ^ transitions, respectivety arising22 from octahedral

geometry of the nickel(ll). The electronic spectra of copper(II)

complexes show two bands in the 18600 - 19100 and 15800-16400

cm" regions which may be ascribed to Bjg -» Eg and Bjg -» B2g

transitions, respectivety, attributable to an octahedral geometry

around copper (II).

All the spectra show very strong intense bands in the ultraviolet

region around 38000 cm"1 which may be assigned to n -» iC

transitions of the ligand. The observed magnetic moment values for

all the complexes [MCl2LSnCl2] are also in accordance with the

proposed octahedral structures.

References \ \ 78

REFERENCES

M.I. Bruce,"Comprehensive Organomelallic Chemistry", G. Wilkinson, F.W. Abel and F.G.A. Stone, 1982, 9, 1209.

M.S. Holt, W.L. Wilson and J.H. Nelson, Chem. Rev., 1989, 89, 11 and the references therein.

M. Shakir, S.P. Varkey, O.S.M. Nasman and A.K. Mohamed, Synth. React. Inorg. Met.-Org. Chem., 1996, 26(3), 509.

M. Shakir, P S . Hameed, F. Firdaus and S.P. Varkey, Transition Met. Chem., 1995, 20, 142.

D. Cunningham, J. Fitzgerald and M. little, J. Chem. Soc. Dalton Trans., 1987, 2261 and the references therein.

D. Cunningham, J.F. Gallagher, T. Higgins, P. McArdle, J. McGinley and M.O'.Gara, J. Chem. Soc. Dalton Trans., 1993, 2183.

L. Pellerito. R. Cefalln, A. Giagnzza and R. barbieri, J. Organomet. Chem., 1974, 70, 303.

D. Cunningham and J. Mchinley, J. Chem. Soc. Dalton Trans., 1992. 1387.

T.N. Srivastava, A.K.S. Chauhan and M. Agarwal, Tranistwn Met. Chem., 1978, 3, 378.

D. Cunningham, T. Higgins, B. Kneafsey, P. McArdle and J. Simmie. J. Chem. Soc. Chem. Commun., 1985,231.

W.J. Geary. Coord. Chem. Rev., 1971, 7, 81.

M. Shakir and S.P. Varkey, Polyhedron 1994, 13, 791.


M. Shakir, S.P. Varkey and T A. Khan, Indian J. Chem., 1995, 34A, 72.

3 References Qi]

A. Varshney and J.P. Tandon, Polyhdedron 1986, 5, 1853.

K. Burgess, D. Lim, K. Kantto and C.Y. Ke, J. Org. Chem., 1994, 59, 2179.

M. Shakir, S.P. Varkey and O.S.M. Nasman, Polyhedron 1995, 14, 1283.

M. Shakir, S.P. Varkey and P.S. Hameed J.Chem. Res., 1993, 11, 442.

M.C. Jain, A.K. Srivastava and P.C. Jain, Inorg. Chim. Acta., 1977, 23, 199.

R.K. Ray and G.B. Kauffman, Inorg. Chim. Acta., 1990, 173, 207.

M. Shakir. S.P. Varkey and P.S. Hameed, Polyhedron 1994, 13, 1355.

A.B.P. Lever, "Inorganic Electronic Spectroscopy", Elsevier, Amsterdam (1984).

Chapter 3 Tetraoxotetraamide Macrocyclic Complexes | [ 80

3.2

SYNTHESIS AND CHARACTERIZATION OF TETRAOXOTETRAAMIDE MACROCYCLIC COMPLEXES

3.2.1 INTRODUCTION

Polyamide macrocycles have received much attention in

view of their biological importance and catalytic applications1"6.

Many of these ligands chelate transition metals as anions via

dissociation of amide protons, giving neutral complexes7"9.Recently

Bu and co-workers have investigated10 the crystal structure of

1,4,7,10 - tetraazacyclotridecane - 11,13 - dione, appended with 8-

methyl-quinolines. and its reactions with copper(II).

Chapter 3 j | Tetraoxotetraamide Macrocyclic Complexes [ \ 81

The structures and properties of macrocyclic dioxotetraamines

are in some respects similar to those of tripeptides. Such ligands

show unique ligating behaviour towards divalent 3d cations with

simultaneous dissociation of two amino groups" . Tripeptides such as

GlyGlyGlyu'u or GlyGIyHis" sh ow similar modes of coordination to

copper through the two terminal donors and the two deprotonated

amide nitrogens in alkaline media. Polyamide macrocycles can in

principle coordinate either through the amide nitrogen or oxygen

atoms. Kaden and Zuberbuhler have concluded15 from potentiometric

studies that the amide nitrogens of GlyHis and HisHis do not co

ordinate to the copper(II) ion. There are other reports' ' which also

indicate that for synthetic peptides, the peptide nitrogens do not

participate in coordination. Following our previous reports on

polyamide macrocycles, this part of the thesis presents the template

synthesis and characterization of novel tetraamide macrocyclic

complexes derived from anthranilic or o-aminobenzoic and succinic

acids with 1,2-diaminoethane and 1,3-diaminopropane.


Succinic acid, anthranilic acid, 1,2-diaminoethane and

Chapter 3 Tetraoxotetraamide Macrocyclic Complexes ] 1 82

1.3-diaminopropane (Merck) were all used as received. MnX2 .4H20,

CoX2 .6H20, NiX 2 .6H 2 0, CuX2 .2H20 (X = CI or N 0 3 ) , Zn(N03)2

6H20 and ZnCl2 (BDH) were used as received. All the solvents were

dried before use.

Dichloro/nitrato(6:7,14 : 15-dibenzo-5,9,12,16-tetraoxo-l,

4,8,13-tetraazacyclohexadecane)metal(II), [ML5X2] [M = Mn1 ,

Co" , Ni" , Cu" and Zn11; X = CI or N 0 3 ] .

A stirred solution of the appropriate metal salt (10 mmol) in

methanol (50 cm3) was treated with a solution of o-aminobenzoic

acid (2.74 gm, 20 mmol) in methanol (65 cm3) and 1,2-diaminoethane

(0.67 cm3, 10 mmol) in methanol (30 cm3), added simultanenously. A

solution of succinic acid (1.18 gm, 10 mmol) in MeOH (50 cm3) was

then added and the reaction mixture was stirred for several hrs. which

led to the precipitation of a solid product. This was filtered off,

washed with MeOH and vacuum dried.

Dichloro/nitrato(7:8,15:16-dibenzo-6,10,13,17-tetraoxo-l ,

5,9,14-tetraazacycloheptadecane)metal(II) , [ML6X2] [M = Mn",

Co" , Ni" , Cu11 and Zn11; X = CI or N 0 3 ) .

The respective metal salt (10 mmol) dissolved in methanol

(50 cm ) was treated with a solution of o-aminobenzoic acid

(2.74 gm, 20 mmol) in methanol (65 cm3) and 1,3-diaminopropane

Chapter 3 Tetraoxotetraamide Macrocyclic Complexes | | 83

(0.74 cm . 10 mmol) in metahnol (30 cm ), added simultaneosuly. A

gradual colour change was observed. Finally a methanolic solution of

succinic acid (1.18 gm, 10 mmol) was added to the mixture, which

was then stirred for several hrs. The resulting solid product was

removed by filtration, washed with methanol and vacuum dried.


A new series of tetraoxotetraamide macrocyclic

complexes have been prepared via the condensation reaction of o-

aminobenzoic acid with 1,2-diaminoethane or 1,3-diamino-propane

and succinic acid in presence of transition metal ions as templates

(Scheme 7). Attempts to prepare metal-free ligands in methanol or

ethanol led to oily products which could not be isolated and

analysed. The elemental analyses of the complexes (Table 5) are

consistent with their suggested stoichiometrics. The complexes are

generally highly coloured and polycrystalline in nature. They are

obtained in a 52-64% yield and are indefinitely

stable in the solid state. The molar conductances of the complexes in

DMSO are low (Table 5), suggesting that they are non-electrolytes20

An examination of the IR spectra (Table 6) of the complexes

[ML X2] and [ML6X2] show a medium intensity band for v(N-H) in

Tetraoxotetraamide Macrocyclic Complexes

CO^H ^ ( C H ? ) n ^

NH, H,N NH,

MX 2

(CH^COjH),

?

^"-l<" TO] PL,,. A

'N.

A L , n = 2 L6, n = 3 M = Mn", Co", Ni", Cu" a n d Z n " X = CI or N 0 3

Scheme 7

Table 5. % Yield, Colour, Melting point, Molar Conductance and Analytical Data for the Compounds.

Compound % Yield Colour Melting Am Found ( C a l c . ) %

P o i n t (cm2Q V s l X) C H N M CI

<°C)

[MnL 5 (N0 3 ) 2 ] 53 O f f - w h i t e 317 2 0 . 5 4 3 . 4 3 . 7 1 4 . 8 1 0 . 1 ( 4 2 . 9 ) ( 3 . 6 ) ( 1 5 . 0 ) ( 9 . 8 )

[MnL5Cl2] 54 A g a t e g r e y 305 2 4 . 0 4 7 . 3 4 . 1 1 0 . 7 1 0 . 4 1 3 . 7 ( 4 7 . 4 ) ( 3 . 9 ) ( 1 1 . 0 ) ( 1 0 . 8 ) ( 1 4 . 0 !

[MnL 6 (N0 3 ) 2 ] 54 Dove g r e y 247 1 5 . 6 4 4 . 1 3 . 9 1 4 . 5 9 . 4 ( 4 3 . 9 ) ( 3 . 8 ) ( 1 4 . 6 ) ( 9 . 5 )

[MnL6Cl2] 52 Shadow grey 287 13.3 47.9 4.1 11.1 10.3 13.3 (48.4) (4.2) (10.7) (10.5) (13.6!

[ C o L 5 ( N 0 3 ) 2 ] 62 G r e y 304 1 7 . 5 4 3 . 0 3 . 5 1 5 . 2 1 0 . 1 ( 4 2 . 6 ) ( 3 . 5 ) ( 1 4 . 9 ) ( 1 0 . 4 )

4 6 . 8 4 . 1 1 1 . 4 1 1 . 3 ( 4 7 . 0 ) ( 3 . 9 ) ( 1 0 . 9 ) ( 1 1 . 5 ) ( 1 3 . 8 )

4 3 . 5 3 . 4 1 4 . 7 1 0 . 3 4 3 . 6 ) ( 3 . 8 ) ( 1 4 . 5 ) ( 1 0 . 2 )

[ C o L 5 C l 2 ] 57 Dim g r e y 318 1 6 . 4 4 6 . 8 4 . 1 1 1 . 4 1 1 . 3 1 4 . 3

t C o L 6 ( N 0 3 ) 2 ] 56 B r i g h t g r e y 248 1 6 . 4 4 3 . 5 3 . 4 1 4 . 7 1 0 . 3

[CoL 6 Cl 2 ] 58 D u l l g r e y 287 1 7 .

[ N i L 5 ( N 0 3 ) 2 ] 64 L i g h t a s h 335 17

[ N i L 5 C l 2 ] 60 Dim a s h 345 12

[ N i L 6 ( N 0 3 ) 2 ] 63 B r i g h t g r e y 2 8 3 12

[ N i L 6 C l 2 J 61 Sky g r e y 314 14

[CuL 5 N0 3 ) 2 ] 58 B r i g h t g r e e n 204 18

[CuL 5 Cl 2 ] 62 Dim g r e e n 234 21

[ C u L 6 ( N 0 3 ) 2 ] 62 B r i g h t g r e e n 339 2 3

[CuL 6 Cl 2 ] 58 Dim g r e e n 248 24

4 7 . 7 : 4 8 . o)

4 . 0 ( 4 . 2 ;

1 0 . 5 ( 1 0 . 6 )

1 1 . 7 ( 1 1 . 2 )

1 3 . 7 ( 1 3 . 5

4 2 . 5 : 4 2 . 6 ;

3 . 7 3 . 5 '

1 5 . 2 14 .91

1 0 . 7 1 0 . 4

4 6 . 8 4 7 . l ;

4 . 1 3 . 9 )

1 1 . 3 1 0 . 9 )

1 1 . 3 1 1 . 5 !

14 (13

4 3 . 5 ; 4 3 . 6 )

3 . 8 ; 3 . 8 )

1 4 . 7 1 4 . 5 1

1 0 . 5 1 0 . 1 )

4 7 . 6 : 4 8 . i ;

4 . 3 : 4 . 2 ;

1 0 . 4 1 0 . 6 ;

1 1 . 5 ( 1 1 . 2 ;

1 3 . 4 1 3 . 5 )

4 2 . 7 4 2 . 2 ;

3 . 7 3 . 5 ]

1 4 . 4 1 4 . 7

1 0 . 7 ( 1 1 . I !

4 6 . 3 4 6 . 6 )

4 . 0 3 . 9 )

1 1 . 1 ( 1 0 . 8

1 2 . 1 1 2 . 3 )

14 (13

0 7]

4 3 . 5 ; 4 3 . 3 ;

3 . 9 ( 3 . 8 )

1 4 . 5 ( 1 4 . 4 )

1 1 . 1 1 0 . 9 )

4 7 . 5 4 7 . 6 !

4 . 3 4 . 1 ;

1 0 . 4 1 0 . 5 ;

1 1 . 8 1 2 . o ;

13 ] 3

7 4)

[ Z n L 5 ( N 0 3 ) 2 ] 54

[ Z n L 5 C l 2 ] 56

[ Z n L 6 ( N 0 3 ) 2 ] 56

[ZnL 6 Cl 2 ] 54

Oyster white 167

Dirty white 199

Dirty white 249

Oyster white 317

20.0 41.9 (42.1)

18.0 46.3 (46.4)

19.0 42.8 (43.1)

18.5 47.6 (47.5)

3.4 14.5 (3.5) (14.7)

4.0 11.1 (3.9) (10.8)

3.6 14.3 (3.7) (14.4)

4.3 10.7 (4.1) (10.5)

.1 ] . 7 (11.4)

12.8 13.4 (12.6) (13.7)

11.3 (11.2)

12.5 13.8 (12.3) (13.3)

Table 6. IR Spectral Data (cm ) for the Compounds.

Compound V(N-H)

I

[ M n L 5 ( N 0 3 ) 2 ]

[ M n L 5 C l 2 ]

[ M n L 6 ( N 0 3 ) 2 ]

[ M n L 6 C l 2 ]

[ C o L S ( N 0 3 ] 2 ]

[ C o L 5 C l 2 ]

[ C o L 6 ( N 0 3 ) 2 ]

[ C o L 6 C l 2 ]

[ N i L 5 ( N 0 3 ) 2 ]

[ N i L 5 C l 2 ]

[ N i L 6 (N0 3 ) 2 ]

3 2 3 0

3 2 3 5

3 2 1 0

3 2 3 0

3 2 1 0

3 2 0 0

3 2 4 0

3 2 1 0

3 2 3 0

3 2 2 0

3 2 1 0

1 6 7 0

1 6 8 0

1 6 9 0

1 6 9 0

16 60

1 6 9 0

1 6 8 0

1 6 8 0

1 6 9 0

1 6 8 0

1 6 8 0

Amide bands V(M-N)

^1 I£I IV

530 1230 660 430

530 1240 670 420

550 1280 650 420

540 1290 670 400

520 1280 665 430

540 1270 675 420

540 1280 670 410

550 1260 665 420

550 1250 680 410

540 1240 660 440

530 1260 670 430

V(M-C1) Ring vibrations

300 1405,1025,725

290 1415,1045,755

285 1420,1060,775

310 1410,1025,750

305 1400,1030,760

310 1420,1020,740

280 1420,1020,740

290 1410,1020,730

300 1410,1060,720

310 1400,1035,735

300 1420,1025,730

m CM

r L D

0 0

o r H

U0

o *r

O LO

r-U0

oo o i—i

L D

I—1

^r

O

CM

r-o X )

O i—(

o i—1

M 1

L O

oo r-o ^ o t-i

o 0 0

«3"

o oo r-i n

ro o <-< o CM

*!*

m ro r o T

o r H

O i—1

^r

o «r r-o <x> o <—( 0 0

CM

•cr

o oo r-o oo o t H

m o ^r

m m r~ o I D

O i - t

o CM

«3*

O Cn CM

oo 0 0 CM

o I—1

0 0

o CM 00

o en CM

o oo CM

i n G\ CM

o en CM

o o 0 0

o T V

o o «3"

o CM

r

o I—1

T

o oo <=r

o CM

r

o r r

o oo T

O i-H

«T

LO X )

X>

0 0

r-X>

o 0 0 IX)

m m 1X1

o r~ 1X3

o r-<x>

o <x> *x>

o CO X )

o CO

<x>

o r-CM

o 0 0

CM

o CM

CM

O

m CM

O i n

CM

O L n

CM

O

r-CM

O

r-CM

o oo CM

o <3"

m

o 0 0 u 0

o m i n

o m m

o X )

i n

o <=r m

o 0 0

m

o ^ T

m

o M*

m

o cn X)

o cn X>

o CO IX

o r-X>

o r-X)

o CO X)

o r-X )

o 0 0 X)

o en X)

o OO

CM 0 0

O 0 0

C\J 0 0

o i—H

CM 0 0

o o CM 0 0

o sr CM

oo

o < CM 0 0

O O

CM 0 0

o CM CM 0 0

O

oo CM

oo

,—, rsi • H

u D H-l • H

X

r o

o 2: --LO

J 3 U

,—, CM i—1

U m

J 3 U

ro

o 2 — ID

J 3 u

, , IN

<-i

u ID

J 3 u

r o

o 2 ~—-

i n

• J

d N

r , CM r—1

U o->

h-5

d CO

ro

o 2

>x> .J d

N

( ! CM

• H

C) >£>

h J

d N

Table 7. H NMR Spectral Data* for the Compounds

Compound NH-C=0 N-CH2 Phenyl ring C-CH2-C C=0-CH2

[ZnL5(N03)2] 8.41(s) 3.13(m) 6.54(m) - 2.86(s)

[ZnL5Cl2] 8.46(s) 3.11(m) 6.52(m) - 2.83(s)

[ZnL6(N03)2] 8.46(s) 3.12(m) 6.62(m) 2.09 (m) 2.83(s)

[ZnL6Cl2] 8.43(s) 3.13(m) 6.60(m) 2.12(m) 2.84(s)

*Chemical shifts (6/ppm) with multiplicities in parenthesis S = singlet and m = multiplet.

Table 8. \ieff Values, Ligand Field Bands observed in the Electronic Spectra (cm1), their Assignments and EPR Spectral


Compound ^eff.

(B.M.)

Band position

(cm1)

Assignments EPR data

8|

[MnL(N03)2] 5.85 28500

20500

24300

Llg Llg

rtlg *T,Q(P)

6A,g -^ 4T,e(F) lgv

l2g<

[MnLXl2]

[MnLf'(NOi)2]

[MnL6CI2]

5.71

5.76

5.78

29000

19800

24500

29100

20000

24200

28700

21000

24100

llg 4 .

Aig >A,g "> T,g(p) "A Alg

6A Alg <(A Alg 6A Alg

6A Alg (,A Alg (,A Alg

—>

->

—»

-»

—>

—»

—>

T2g(

p)

Aig 4T l g(P) 4T 2 g(F)

4A Alg

4T,g(P) 4T2g(F)

oo oo

t t

^oo ""oo

00 00

t T

"^00 ""Bo

A-t t

££ j - r

8 » < H

T T

^00 ""OO

00 00 00 <N — —

H H H r*", c \ c^

t t t 00 00 00

00 00 00 <N — —

H E- H r , r r *v,

T t T 00 00 00

o o I T ) T —

o o VO O (N

O O <N T •—

O o T f

o ( N

O o r< l -3-—

o o I T )

o CN

o o r-~ TT —

O o f S o <N

o o r—i

(N —

O O v£> ON

—

o o o t-~-(N

o o o (N —

o o u- i O N

> — '

O O m c-~ 04

TI-«r> TT

TJ-

^r T T

r<->

c i

O

<-~>

o H J

o U

(NO

- J O

u

CJ O

J o CJ

rr, O z

>/-l

J

z

u -J

z

a-o o*

V/~>

CN NO

NO vO VO

ON NO t~-

CN CN <N CN

CN

CN

CN

CN

CN

CN

r«1 CN

CN

oo âo ôo fN — —

H F- H

T t t SO 5 0 0 0

oo ôo ' T o fN — —

H H H f", r*-. r*-,

T T T oo oo oo CM fN CM

<: < < C", r*\ r*\

00 fN W CQ

t t oo oo

CQ CQ fN fN

00 00 7i

W CQ fN fN

t t 0 0 0 0

OQ CQ fN fN

0 0 fN tU CQ

fN fN

T t oo oo

ffl CQ fN fN

OO fN UJ CQ

fN fN

t t oo oo

CQ CQ fN fN

o o rr CN

O © C"> O

O o r—

r«-

o o o CN

o o •3-&

© o — r-~

o o I T ) 00

o ir> vO i r .

O m NO oo

o o o NO

o o 0 0 0 0

© © m vO

© o m 00

© © ON I T !

NO CN 00 ON oo

© 00

o' z

z

fN

3 -J 3

u

o z 3

u 3

Chapter 3 | Tetraoxotetraamide Macrocyclic Complexes | | 94

the 3200-3240 cm"1 region. This band shows a marked negative shift4

in all the complexes which may be due to the coordination of

nitrogen to the metal atom. This is further supported by the

appearance of a new band for v(M-N) in the 400-440 cm"1 region.

Medium to strong intensity bands observed in the ca. 1690, 1540,

1270 and 660 cm"1 region in the spectra of all the complexes may be

assigned to amide I, amide II, amide III and amide IV vibrations,

respectively. The amide I [v(C=0)] band occurs at almost the same

position as in the analogous metal-free macrocycles21, indicating the

non-involvement of carbonyl oxygen in the complexation. All the

chloro complexes have bands at ca. 300 cm"1 assignable to v(M-Cl)

vibration. The nitrate complexes have bands at ca. 1035, 1290 and

1490 cm"1 assigned to Vi. v2, and v3 of monodentate coordinated

nitrate respectively22. The bands corresponding to the phenyl ring

vibrations are observed at their expected positions.

The H NMR spectra (Table 7) of the zinc complexes in

DMSO-</6 solution showed no signals assignable to the carboxylic or

primary amino protons. All the complexes gave a broad signal in the

8.41-8.46 ppm, range assigned to the amide protons (NHCO, 4H). A

multiplet at 6.52-6.62 ppm. in all of the complexes is characteristic

Chapter 3 Tetraoxotetraamide Macrocyclic Complexes 95

of phenyl ring (C6H4, 8H) protons, whilst a singlet at 2.83-2.86 ppm

may be ascribed to the methylene (COCH2, 4H) protons of succinic

acid moiety. A multiplet observed for all the complexes in the 3.11-

3.13 ppm region may be assigned19 to the (CH2N, 4H) methylene

protons. The complexes of "L6" showed an additional multiplet

around 2.12 ppm attributable to the central methylene protons

(CCH2C, 2H) due to propylene bridge.

The room temperature EPR spectra (Table 8) of the

copper(II) [CuL5X2] and [CuL6X2] complexes gave g ( and gx values in

the 2.21-2.26 and 2.11-2.16 regions, respectively. All complexes

gave similar spectra; the absence of hyperfine splitting indicates that

the paramagnetic centres are not diluted. Copper(II) complexes in

which g| > gx are considered to have the unpaired electron in the

• 23 dx, v, orbital . The G parameters, obtained by the relati on

(g«"2) /(gx-2), were in the 1.625-1.909, range suggesting a

considerable exchange interaction between the copper centres24. The

EPR of the cobalt complexes at room temperature gave only a single

broad signal exhibiting gy and gx around at ca. 2.04 and 2.32

respectively, characteristic of d7 cobalt(II) complexes2 5 2 6 .

The electronic spectra (Table 8) of manganese complexes

exhibit three bands at around 29000, 20000 and 24300 cm"1 regions,

Chapter 3 Tetraoxotetraamide Macrocyclic Complexes | | 96

assignable to 6A, -> 4A, , 6A, -> 4T, (P) and ° lg lg ' !g l g v '

6Aj -> 4T2 (F) transitions, respectively, suggesting24 an octahedral

stereo-chemistry of manganese ion. The ligand field transitions of

cobalt complexes have been recognised at around 14500 and 20400

regions, which may unambiguously be assigned as

4Tj (F) -» 4A2 (F) and 4T, (F) ->• 4Tj (P) transitions, respectively in

octahedral symmetry.

The nickel(II) complexes showed the appearance of three

bands around 12100, 19400 and 27100 cm'1 which may be attributed

to the 3A, -> 3 T, 3A, -> 3T, (F) and 3A2„ -> 3T,„(P) transitions, 2g 2g i 2g l g v ' ^ < s ' e v '

respectively, indicating the octahedral geometry with A ground

state. Copper(II) complexes exhibit two distinct bands centred in the

18300-18800 and 15650-16300 cm"1 regions assignable to 2B, -> 2E

and 2 B, -> 2 B, transitions respectively which is characteristic of an 1 g 2g r J

octahedral geometry.

The magnetic moments obtained from the manganese(II).

cobalt(II), nickel(II) and copper(II) complexes also are entirely

consistent with six-coordination at the metal centres.

References 1 [ 971

REFERENCES

E. Kimura, T. Yatsunami, A. Watanaba, R. Michida, T. Koike, H. Fujioka, Y. Kuramoto, M. Sumomogi, K. Kunimitsu and A. Yamashita, Biochim. Biophys. Acta., 1983, 37, 745.

M.C. Shen, Q.H. Lou, S.R. Zhu, Q.Y. Tu, A.D. Liu, H.C. Gu, F.M. Li and S.J. Di, Chem. J. Chinese Univ. Ser., B, 1990, 6, 354.

R.S. Drago, B.B. Cordon and C.W. Barnes, J. Am. Chem. Soc, 1986, 08, 2453.

M. Shakir and S.P. Varkey. Polyhedron 1995, 14, 1117.

M. Shakir, O.S.M. Nasman, A.K. Mohamed and S.P. Varkey, Polyhedron 1996, 15, 2869.

M. Shakir and S.P. Varkey, Transition Met. Chem., 1994, 19, 606.

E. Kimura, J. Coord. Chem., 1986, 1, 15; E. Kimura, Pure Appl. Chem., 1986, 58, 1461.

M. Kodama and E. Kimura, J. Chem. Soc. Dalton Trans., 1979, 1783.

M. Shionoya, E. Kimura and Y. Litaka, J. Am. Chem. Soc, 1990, 112, 237.

X.H. Bu, D C . An, Y.T. Chem. M. Shionoya and E. Kimura, J. Chem. Soc. Dalton Trans., 1995, 2289.

M. Kodama and E. Kimura, J. Chem. Soc. Dalton Trans., 1979, 325.

Chapter 3 References i cm

12. M.K. Kim and A.E. Martell, J. Am. Chem. Soc, 1966, 88, 914.

13. A.P. Brunatti, M.C. Lim and G.H. Nancollas, J. Am. Chem. Soc, 1968, 90, 5120.

14. R.P. Agarwal and D.P. Perrin, J. Chem. Soc Daiton Trans., 1977, 53.

15. T. Kaden and A. Zuberbuhler, Helv. Chim. Acta., 1966, 49, 2189.

16. P.A. Temussi and A.Vitagoliano, J. Am. Chem. Soc, 1975, 97, 1572.

17. Y. Suguiro, Inorg. Chem., 1978, 17, 2176.

18. T.A. Khan, S.S. Hassan, S.P. Varkey, M.A. Rather and M. Shakir, Transition Met. Chem., 1996, 21, 1.

19. M. Shakir, S.P. Varkey and T.A. Khan, Indian J. Chem., 1995, 34A, 72.

20. W.J. Geary, Coord. Chem. Rev., 1971, 7, 81.

21. K. Nakamoto, "Infrared Spectra of Inorganic and Coordination Compounds", Wiley Interscience, New York, 1970.

22. P.W. Ball and A.B. Blake, J. Chem. Soc, (A), 1969, 1415.

23. M.C. Jain, A.K. Srivastava and P.C. Jain, Inorg. Chim. Acta., 1977, 23, 199.

24. A.B.P. Lever, "Inorganic Electronic Spectorscopy", Elsevier, Amsterdam, 1984.

25. J. Chem. N. Ye, N.W. Alcock and D.H. Busch, Inorg. Chem.. 1993, 32, 904.

26. M.G.B. Drew, F.S. Esho and S.M. Nelson, J. Chem. Soc. Daiton Trans., 1983. 1653.

Chapter 3 Tetraiminetetraamide Macrocyclic Complexes | | 99

3.3

SYNTHESIS AND SPECTROSCOPIC STUDIES OF TETRAIMINETETRAAMIDE MACROCYCLIC COMPLEXES

3.3.1 INTRODUCTION

The polyamide macrocycles deserve special attention as

in some cases these macrocycles have been used for the construction

of the corresponding polyaza macrocyclic complexes1 . In view of the

continued interest in polyamide macrocycles, various macrocyclic

complexes bearing amide groups have been reported recently2 \ from

different reactions. Schiff-base ligands containing N=C-C=N

structural unit, forming a strong chelate ring have been of great

interest, because of electron dereal iza t ion and conjugation of the

Chapter 3 Tetraiminetetraamide Macrocyclic Complexes 1 | 100|

ligand which may affect the nature of the complex formed4. However,

till date only a few complexes with such ligands have been

reported5"7. We have very recently reported the template synthesis of

various polyamide macrocyclic complexes8"1 and have a long term

interest in producing polyamide macrocyclic complexes of a wide

variety. In this study, we report a new series of tetraiminetetraamide

"7 "7

macrocyclic complexes of the type [ML X2] and [CuL ]X2 [M =

Mn", Co11, Ni" and Zn"; X = CI or N0 3 ] obtained by the template

condensation of l ,2-diphenylethane-l,2-dione dihydrazone

(DPEDDH) and dimethyl or diethyloxalate.


The chemicals benzil, hydrazinehydrate (Merck),

dimethyl and diethyloxalate (both Fluka) were used as received. The

metal salts MX2 .6H20 (M = Co" or Ni11), MnX2 .4H20, CuX2 .2H20 (X

= CI or N0 3 ) , ZnCl2 and Zn(N0 3) 2 .6H 20 (all BDH) were

commercially pure samples. l,2-Diphenylethane-l,2-dione

dihydrazone (benzildi-hydrazone) was prepared by the reaction of the

benzil and hydrazinehydrate in methanol in 1:2 molar ratio. Benzil

(1.05 gm, 5 mmol) was dissolved in MeOH (75 cm3) and kept

magnetically stirred in a round-bottomed two-necked flask.

Chapter 3 Tetraiminetetraamide Macrocyclic Complexes | | 1011

Hydrazinehydrate (48 cm3, 10 mmol) was added to the stirred

mixture. The resultant mixture was stirred for 8 hrs. The solid

product was filtered off and washed several times with methanol. The

chalky white product thus obtained was dried over fused CaCl :

Dichloro/nitrato(6,7,14,15-tetraoxo-2,3,10,ll-tetraphenyl-l,

4, 5, 8, 9, 12, 13, 16-octaazacyclohexadecane-l, 3, 9, 11-tetraene)

metal(II), |M L7X2] [M = Mn", Co", Ni", and Zn"; X = CI or

N 0 3 ] and (6, 7, 14, 15-tetraoxo-2, 3, 10, 11-tetraphenyl-l, 4, 5, 8,

9, 12, 13, 16-octaazacyclohexadecane-l, 3, 9, l l-tetraene)copper(lI)

chloride/nitrate ICuL7]X2 [X = CI or N 0 3 ] .

A gradual colour change was observed when a sample (1.191

gm, 20 mmol) of l ,2-diphenylethane-l,2-dione dihydrazone

(DPEDDH), suspended in CH2C12 (150 cm3), was treated with a

methanolic (65 cm3) solution of metal salt (10 mmol) and dimethyl

(0.51 cm3, 20 mmol) or diethyloxalate (0.68 cm3, 20 mmol)

simultaneously. The reaction mixture was stirred for 8 hrs. and then

it was refluxed for 13 hrs. The product obtained was filtered off,

washed with CH2CI2 and dried over fused CaCI2 kept in a desiccator.

Chapter 3 Tetraiminetetraamide Macrocyclic Complexes 102


Novel tetraiminetetraamide macrocyclic complexes

[ML7X2] and [CuL7]X2 [M = Mn", Co", Ni11 and Zn11; X = CI or N0 3 ]

have been prepared by the condensation reaction of 1,2-dip-

henylethane-l,2-dione dihydrazone (DPEDDH) with dimethyl or

diethyloxalate followed by metal templation in 2:2:1 molar ratio

(Scheme 8). Both starting materials dimethyl or diethyloxalate were

used with each metal leading to the identical products. The

complexes examined show poor solubility in solvents like,

chloroform, carbon tetrachloride and water. However, they are freely

soluble in dimethylsulphoxide and warm dimethylformamide The

elemental analyses (Table 9) results agree well with the mononuclear

structure. The molar conductivities in DMSO indicate11 '1 that

copper(II) complexes are electrolytic while others are non-

electrolytic in nature.

The IR spectra (Table 10) of all the complexes are similar but

strikingly different from the spectra of free ligand. The spectra of

free ligand (DPEDDH) shows two strong, medium intensity

prominent bands at 3290, 3210cm"!, assignable to v(N-H) vibrations

of amino groups which occur at slightly lower frequencies than are

usually associated with v(N-H) vibrations of

Chapter 3 Tetraiminetetraamide Macrocyclic Complexes 103

Ph Ph

H o o

IHjN—NH ?

Stirring M»OH

H , M - N

> /

Ph

Ph

X N - N H ?

0 0

M RO OR

RtCH3W C j H 5

Ph Ph

- \ | N N ^ O <W ^ N — N N

H Ph Ph

Ph p

O C7

\ / Cu

M Ph Ph

1 ?•

M = Mn", Co", Ni», and Zn" A = CI or N 0 3

Scheme 8

Table 9. % Yield, Colour, Meiting point, Molar Conductance and Analytical Data for the Compounds.

Compound % Y i e l d C o l o u r M e l t i n g Am — P o i n t (Gm2C2_1mol_1) C <°C)

Found ( C a l c . ) %

H N M CI

DPEDDH 61

[MnL 7 (N0 3 ) 2 ] 4 8

[MnL7Cl2 ; 51

[ C o L 7 ( N 0 3 ) 2 ] 53

White

Pink

167

185

Light pink 193

Bright pink 210

21.5

18.6

19.9

70.8 ;70.5)

50.7 !50.3)

54.6 :54.1)

6.0 [5.9!

3.6 ; 3 . 2 )

3.7 : 3 . 4 )

2 4.0 !23.5)

18.7 [18.3)

16.2 ;i5.8)

7.4 (7.2)

8.2 (7.8)

50.3 3.3 18.5 7.2 (50.0) (3.1) (18.2) (7.6)

10.2 ( 9 . 8 :

[CoL Cl2] 48 Light pink 221 17.5 54.2 : 5 3 . s ;

3.0 :3.4;

16.1 15.7)

7.8 !8.2)

10.3 (9.8)

[NiL (N03)2: 51 Green 195 20.5 50.5 :50.i;

3.5 3.1)

18.7 18.2)

7.3 7.5;

[NiL7Cl2] 51 Dim g r e e n 205 2 1 . 0

[CuL 7 ] (N0 3 ) 2 53 Brown 215 107

[CuL7]Cl2 55 Dark brown 221 98

;ZnL7(N03)2] 54 White 190 19 .4

[ZnL7Cl2] 53 O f f - w h i t e 197 18 .7

* D i m e t h l y o x a l a t e was u s e d a s t h e s t a r t i n g m a t e r i a l

DPEDDH = 1, 2 - d i p h e n y l e t h a n e - 1 , 2 - d i o n e d i h y d r a z o n e

54 . 3 ( 5 4 . 0 )

4 9 . 7 ( 4 9 . 2 )

5 3 . 9 ( 5 3 . 4 )

5 0 . 2 ( 4 9 . 7 )

5 3 . 7 ( 5 3 . 4 )

3 . 1 ( 3 . 4 )

3 . 4 ( 3 . 1 )

3 . 0 ( 3 . 3 )

3 . 5 ( 3 . 1 )

3 . 7 ( 3 . 3 )

1 5 . 3 ( 1 5 . 7 )

1 8 . 4 ( 1 8 . 1 )

1 5 . 3 ( 1 5 . 6 )

1 8 . 5 ( 1 8 . 1 )

1 5 . 2 ( 1 5 . 6 )

7 . 7 ( 8 . 1 )

8 . 4 ( 8 . 2 )

7 . 8 ( 8 . 1 )

8 . 5 ( 8 . 9 )

9 . 3 ( 9 . 0 )

9 . 4 ( 9 . 8 )

-

9 . 3 ( 9 . 7 )

-

1 0 . 2 ( 9 . 7 )

Table 10. IR Spectral Data (cm x) for the Compounds.

Compound V(NH2/NH)

I

DPEDDH 3290 ,3210 -

[MnL 7 (N0 3 ) 2 ] 3250 1690

[MnL 7Cl 2] 3270 1680

[ C o L 7 ( N 0 3 ) 2 ] 3275 1 7 1 0

[ C o L 7 C l ? ] 3 2 7 5 1 6 9 5

[ N i L 7 ( N 0 3 ) 2 ] 3 2 6 5 1 7 0 0

[ N i L 7 C l 2 ] 3240 1 7 1 5

[CuL7] ( N 0 3 ) 2 3250 1 6 9 5

[ C u L 7 ] C l 2 3245 1 6 8 0

Amide b a n d s V(C=N)

I I I I I IV

1 6 1 5

1530 1240 650 1 5 9 5

1510 1 2 5 5 670 1580

1520 1 2 4 5 640 1 5 8 0

1 5 2 5 1230 635 1590

1540 1 2 3 5 665 1 5 9 5

1530 1 2 5 0 650 1 5 8 5

1545 1250 670 1580

1550 1 2 4 5 655 1 5 9 0

V(M-N) R i n g v i b r a t i o n s

1 2 4 5 , 1 0 2 5 , 8 7 5

440 1 2 3 0 , 1 0 1 5 , 8 6 0

425 1 2 3 5 , 1 0 1 0 , 8 5 5

460 1 2 4 0 , 1 0 2 5 , 8 6 5

470 1 2 2 5 , 1 0 3 0 , 8 7 0

450 1 2 4 0 , 1 0 2 0 , 8 4 5

435 1 2 3 0 , 1 0 2 5 , 8 6 0

455 1 2 3 5 , 1 0 1 0 , 8 4 0

450 1 2 2 5 , 1 0 0 5 , 8 7 5

[ Z n L ' ( N 0 3 ) 2 ] 3250 1685

[ZnL C l 2 ] 3265 1690

DPEDDH - 1, 2 - d i p h e n y l e t

1535 1230 655 1595

1520 1225 635 1585

a n e - 1 , 2 - d i o n e d i h y d r a z o n e .

450

445

1230,1015,855

1240,1010,850

Table 11. H NMR Spectral Data* for the Compounds.

Compound

DPEDDH

[ZnL7(N03)2]

[ZnL7Cl2]

N-NH-C

.42 (s;

• 45(s)

N-NH2

4.92 (s;

Phenyl ring protons

7.18(m)

6.90(m)

6.97(m)

emical shifts (5/ppm) with multiplicities in parenthesis s ~ singlet and m = multiplet

Table 12. neff Values, Ligand Field Bands observed i


Compound

fMnL7(NOj)2]

[MnL7CI2]

[CoL7(N03)2]

[CoL7Cl2]

[NiL7(NO,)2]

(B.M.)

5.75

5.70

4.65

4.57

3 18

Band position

-u (cm )

18650 22550

18850

22400

16200 21400

15950

21700

18200 24350

in the Electronic Spectra (cm1), their Assignments and EPR Spectral

Assignments

6A,g -* 4T,g(P) 6Aig -> 4T2g(F)

%g - • 4T,g(P) 6A,g -> 4T2g(F)

4T,g(F) -> 4A2g(F) 4T,g(F) - • 4T,g(P)

4T,g(F) -> 4A2g(F) 4T,g(F) -> 4T,g(P)

A2g(F) 3A2g(F)

Tig(F)

'T,g(P)

8|

EPR data

oo

oo o o

fN

fN

Li. 0 . "so "so

t T

"3D 56 < <

» a „ CM — 6 0

CQ < tU fN fS fN

T T T so so so

CQ 03 CO <N fN fN

5 0 M w , fN — SO

co < to fN fN fN

A .*> /f.

i i T so so so

CO CQ CQ fN fN fN

o I T )

r-00 —

o o (N •—• fN

O i n r-— —

o »o o • o —

o o l/~i

~ (N

o vn T (N —

© O © \D —

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u

Chapter 3 Tetraiminetetraamide Macrocyclic Complexes | | 111]

primary amino groups7. This result is expected because of the high

degree of conjugation in the ligand as the interaction of amino group

lone pair with conjugated groups weakens the N-H bond. The v(C=N)

vibration band appeared at 1615cm"1, which is found to be slightly

negatively shifted than that usually found for the azomethine linkage,

further confirm the dereal izat ion of electrons in the free ligand.

The most singnificant feature of IR spectra of the complexes is

the appearance of four characteristic13 amide bands in the 1680-1715,

1510-1550, 1225-1255 and 635-670 cm"1 regions. The amide I,

v(C=0), is observed in the region expected for the metal-free amide

group ruling out the possibility of coordination through amide

oxygen. The complexes gave a single sharp v(N-H) band in 3240-

3275 cm'1, region, which is found similar to analogous metal-free

tetraaza ligand14. This indicates that the amide nitrogens do not

involve in coordination.

Reported macrocyclic complexes exhibit a strong intensity band

in the range of 1580-1595 cm"1 assignable13 to the coordinated

v(C=N). There is observed increase in the v(C=N) band intensity

which may be due to the possible transformation of trans-structure of

the free ligand (DPEDDH) into cis configuration upon complexation.

The c/5-structure is stabilized by the chelate ring, lowering the

Chapter 3 | [ Tetraiminetetraamide Macrocyclic Complexes | | 112

symmetry which consequently enhances the v(C=N) band intensity.

The bands at 425-470 cm"1, originate from (M-N) vibration. In

addition, the 1R spectra of nitrato complexes exhibit bands at 1280,

1040 and 850 cm'1 which are consistent with the monodentate

nature16 of this group. However, the phenyl ring vibrations appear at

their expected positions.

The ]H NMR spectra (Table 11) of benzildihydrazone

(DPEDDH) and the corresponding zinc complexes have been

recorded and compared. Benzildihydrazone shows a multiplet at 7.18

ppm and a slightly broad signal at 4.92 ppm assignable to the

phenyl ring (C6H5, 10H) and amino (N-NH2, 4H) protons of the

hydrazone moiety. Both the zinc complexes showed the appearance of

a band at 8.42, 8.45 ppm, reasonably ascribed18 to amide (N-NH-

C,4H) protons. A multiplet at 6.90, 6.97 ppm in both complexes is

characteristic of phenyl ring (C6H5, 20H) protons. Absence of

characteristic peaks corresponding to the protons of hydrazone and

oxalate moieties, further confirm that the cyclization has indeed

taken place.

The room temperature EPR spectra (Table 12) of both

polycrystalline Cu(II) complexes exhibit a similar single broad

absorption band. However, no complex is found to give hyperfine

Chapter 3 Tetraiminetetraamide Macrocyclic Complexes j | 113}

splitting. The calculated gj and gi values appeared in the region

2.31, 2.34 and 2.08, 2.09 respectively, which support the contention

that dx2 /2 may be the ground state of the unpaired electron. Both the

complexes studied show g|| > 2.3, indicating appreciable ionic

character19. The g values are related by the expression G = (g|-2)/

(g±-2) and the present complexes [CuL7]X2 [X = CI or N0 3 ] gave

axial symmetry parameter, G at the 3.875, 3.777 region, indicating

considerable exchange interaction among copper(II) ions in these

complexes, as the G values are less than 4.

The electronic spectra (Table 12) of manganese gave two bands

in the 22400-22550 and 18650-18850 cm"1, regions which may be

assigned to 6 A l g -> 4T2g(F) and 6 A l g -> 4T,g(P) transitions

respectively, corresponding to an octahedral environment around the

Mn11 ion. The cobalt complexes exhibit two ligand field bands in the

21400-21700 and 15950-16200 cm"1, regions which may reasonably

correspond to 4T l g(F) -> 4T l g(P) and 4T,g(F) -» 4A2g(F) transitions,

respectively, consistent with octahedral geometry21 around the Co

ion. All the nickel complexes exhibit two electronic bands in

21200 - 24350 and 18200 - 18750 cm"1, regions which may be

ascribed to 3A2g(F) -> 3T l g(P) and 3A2g(F) -> 3T l g(F) transitions,

respectively, suggesting22 an octahedral coordination around the

Chapter 3 | Tetraiminetetraamide Macrocyclic Complexes 114

metal ion. Magnetic moment values are in close agreement with their

electronic spectral.data which further support the proposed geometry.

The observed magnetic moments of Cu(II) complexes fall in the

range 1.87, 1.92. B.M. The electronic spectra of these complexes

show a broad band maximum at 16050 cm"1 which may be assigned to

B l g -» Aig transition. However, two weak shoulders appearing in the

regions 21500-21750 and 11750-12450 cm"1 may be attributed to 2 B l g

7 7 9 T 1

-> 'Eg and B ] g —> B2g transitions, respectively, suggesting a

square-planar geometry around the Cu11 ion.

References | \ 115[

REFERENCES

M. Shakir and S.P. Varkey, Indian J. Chem., 1995, 34A, 355 and the references therein.


M. Shakir, O.S.M. Nasman, A.K. Mohamed and S.P. Varkey, Polyhedron 1996, 15, 2869.

S. Padhye and G.B. Kauffman, Coord. Chem. Rev., 1985, 63, 127.

C. Matsumoto and K.S.N.K. Zasshi, Chem. Abstr., 1967, 88, 340; 1967, 67, 58963.

T.W. Bell and A.T. Papoulis, Angew Chem. Int. Edn. Engl, 1992, 31, 749.

A. Arquero, M.A. Mendiola, P. Souza and M.T. Sevella, Polyhedron 1996, 15, 1657.

T.A. Khan, S.S. Hasan, A.K. Mohamed, K.S. Islam and M. Shakir, Synth. React. Inorg. Met.- Org. Chem., 1997(Accepted).

T.A. Khan, S.S. Hasan, S.P.Varkey, M.A. Rather, N. Jahan and M. Shakir, Transition Met. Chem., 1997, 22, 4.

T.A. Khan, M.A. Rather, N. Jahan, S.P. Varkey and M. Shakir, Transition Met. Chem., 1997 (in press).

W.J. Geary, Coord. Chem. Rev., 1971, 7,82.

M. Shakir, S.P. Varkey and P.S. Hameed, Polyhedron 1994, 13, 1355.


D.H. Cook and D.E. Fenton, Inorg. Chim. Acta., 1977, 25, L95.


15. J. Nelson, B.P. Murphy, M.G.B. Drew, P.C. Yates and S.M. Nelson, J. Chem. Soc. Dalton Trans., 1988, 1001.


17. M. Shakir, A K. Mohamed, S.P. Varkey, O.S.M. Nasman and Z.A. Siddiqi, Polyhedron 1995, 14, 1277.

18. D. Parker, K. Pulukkody, F.C. Smith, A. Batsanov and J.A.K. Howard, J. Chem. Soc. Dalton Trans., 1994, 689.

19. I S . Ahuja and S. Tripathi, Indian J. Chem., 1991, 30A, 1060.

20. I.M. Proctor, B.J. Hathway and P. Nicholls, J. Chem. Soc, (A), 1968, 1678.

21. A.B.P. Lever, "Inorganic Electronic Spectroscopy", Elsevier, Amsterdam (1984).

22. E. Kimura, J. Coord. Chem., 1986, 15, 1.

23. M. Shakir, S.P. Varkey and P.S. Hameed, Polyhedron 1993, 12, 2775.

Chapter 3 Bis(macrocyclic) Complexes | | 117[

3.4

SYNTHESIS AND CHARACTERIZATION OF BIS(MACROCYCLIC) COMPLEXES

3.4.1 INTRODUCTION

Recently, a series of investigations has reported the

introduction of macrocyclic ligands which are able to encapsulate

two metal i o n s ' 2 . Many researchers have prepared numerous

binuclear macrocyclic complexes where one of the metal sites

exhibits coordinative saturation and the other metal is in a

coordinatively unsaturated site 4. Such complexes largely have been

employed for the study of the redox behaviour accompanying

dioxygen binding to metals. The isolation of bis(macrocyclic)

Chapter 3 | | Bis(macrocyclic) Complexes | | 118

nitrogen donor ligands with binuclear coordination sites for transition

metals has attracted much interest and a variety of systems have been

reported5"9 Fenton10 has reviewed this class of compounds

emphasizing their relevance to bioinorganic model systems. Recent

studies on bimetallic bis(cyclam) compounds reveal that many such

compounds can be used as electrocatalysts for the reduction " of

0 2 , C 0 2 or H 2 0 and it was proven that bis(cyclams) containing two

metals are better electrocatalysts than those of the corresponding

mononuclear species. Several articles have been reported in recent

years on the coordination chemistry of bis(macrocyclic) molecules in

which two potentially coordinating tetraaza subunits are linked

together by bridging amine nitrogen or carbon atoms of the ligand's

backbone14"17. In such compounds each tetraaza unit may coordinate a

metal ion and the two metal centres may display independent or

interdependent behaviour based on the length of the bridge joining

the two subunits. This study deals with the synthesis and

characterization of a new series of bis(macrocyclic) complexes

bridged with a benzidine moiety and in this study we are interested

in generating the more unusual situation where the two macrocyclic

rings are far from each other and in which the two encapsulated metal

centres can act as independently as possible.

Chapter 3 Bis(macrocyclic) Complexes


The metal salts, benzidine and formaldehyde were obtained

from E. Merk & Co. Tnethylenetetraamine was obtained from

Aldrich Chemicals.

Dichloro/nitrato[ 1,1-phenyl bis(3,6,9,12-tetrahydro-l,3,6,

Q II

9,12 - pentaazacyclotrldecane))metal(II), IM2L X4] [M = Mn ,

Co", Ni", Cu11 and Zn11 ; X = CI or N0 3 J.

To a stirred methanol (25 cm3) solution of benzidine (0.920

gm, 5 mmol) and 35% aqueous formaldehyde (2 cm3, 20 mmol)

in a two-necked round-bottomed flask was added a methanol (50 cm )

solution of the metal salt (10 mmol) and triethylenetetraamine (0.98

cm3, 10 mmol) simultaneously. The resulting mixture was stirred for

about 7 hrs. and the solid product thus obtained was filtered, washed

with methanol and vaccum dried.


A new series of bis(macrocyclic) complexes, [M2L X4] [M

= Mn11, Co", Ni", Cu" and Zn11; X = CI or N03] have been

synthesized by the template reaction of benzidine, formaldehyde and

triethylenetetraamine in 1:4:2 molar ratio (Scheme 9). All complexes

Chapter 3 Bis(macrocyclic) Complexes | 1 120]

are stable to the atmosphere and are polycrystalline in nature.

Elemental analyses (Table 13) agree well with the bis(macrocyclic)

complexes formulated as shown in Scheme 9. The molar conductance

values in DMSO are supportive of the non-electrolytic nature of all

complexes18.

The important IR spectral results are presented in Table 14. In

all the complexes, a single sharp band observed around 3210 cm"

may be assigned19 to v(N-H) of the coordinated secondary amino

groups. Along with these results, the most important feature is that

the IR spectra of the complexes gave no bands assignable to primary

amino or carbonyl group stretching modes. These data are consistent

with the suggested structure. The bands corresponding to phenyl

group vibrations appear at their expected positions

(Table 14). The IR spectra of all the complexes gave bands around

1170 cm"1 which may be assigned to the v(C-N) vibration. All the

complexes show absorption bands around 2910 and 1450 cm"

corresponding to v (C-H) and 8(C-H) vibrations, respectively. The

chloro complexes display a medium intensity band in the 310-

330 cm region which may be attributable to an M-Cl stretching

vibration. Furthermore, the appearance of a medium intensity band

Bis(macrocyclic) Complexes

H,N NH2 / HCHO

+

1 H2N N H NH 2

H V X / H H \ x / "

M = M n " , C o " , Ni" , C u " and Z n " X = CI or N 0 3

Scheme 9

Table 13. % yield, Colour, Melting point, Molar Conductance and Analytical Data for the Compounds.

Compound % Yield Colour Melting Am Point (cm^'mor1)

(°C)

Found (Calc.)%

H N M CI

[Mn2L8(NO04] 68 Iron grey

[Mn2L8Cl4]

[Co2L8Cl4]

[Ni2L8(NOi)4]

65 Yew green

[Co2L8(NO,)4] 71 Dark brown

62 Off grey

59 Frost grey

310

317

192

239

317

13.0

12.5

13.5

12.5

15.0

37.7 (38.1)

42.8 (43.3)

38.2 (37.7)

43.0 (42.8)

38.1 (37.8)

5.5 (5.4)

6.7 (6.2)

5.2 (5.4)

5.8 (6.1)

5.3 (5.4)

22.7 (22.2)

17.5 (18.0)

21.7 (22.0)

18.3 (17.9)

21.6 (22.0)

11.9 (12.4)

13.5 18.7 (14.0) (18.2)

13.7 (13.2)

13.7 17.5 (14.0) (18.0)

12.7 (13.0)

[Ni2L8Cl4] 58 Castor grey 315 11.5

[Cu2L8(NO.0.,J 75 Slag 327 13.5

[Cu2L*Cl4] 74 Dim green 198 17.5

[Zn2L8(N03)4] 64 Colourless 316 15.5

[Zn2L8CL] 61 Dirty white 191 17.5

42.5 5.7 18.4 15.1 17.8 (42.8) (6.1) (17.9) (14.8) (18.0)

36.9 5.8 22.1 13.8 (37.3) (5.3) (21.7) (14.0)

41.8 5.5 17.5 16.4 18.3 (42.3) (6.0) (17.1) (16.0) (17.8)

36.7 5.6 22.2 13.9 (37.2) (5.3) (21.7) (14.4)

41.6 5.7 18.1 16.6 18.1 (42.1) (6.0) (17.6) (16.2) (17.7)

Table 14 . IR S p e c t r a l Data (cm 1) f o r t h e Compounds.

8

Compound V(N-H) v(C-H) v(C-N) v(M-N) 8(C-H) V(M-Cl) NO3 group vibrations Ring vibrations

[Mn2L (N03)4] 3220 2910 1180 470 1450 - 1060,1300 1410,1030,720

[Mn2L Cl4] 3200 2900 1170 440 1440 310 - - 1430,1050,760

[Co2L (N03)4] 3210 2920 1170 440 1450 - 1050,1300 1410,1060,740

p

[Co2L Cl4] 3210 2890 1170 440 1460 330 - - 1420,1020,780

p

[Ni 2 L (N0 3 ) 4 J 3220 2 9 1 0 1160 430 1 4 4 0 - 1 0 6 0 , 1 2 6 0 1 4 4 0 , 1 0 4 0 , 7 3 0

p

[Ni 2 L C l 4 ] 3210 2 9 0 0 1170 450 1440 310 - - 1 4 2 0 , 1 0 4 0 , 7 3 0

p

[Cu2L (N03)4] 3220 2920 1180 450 1450 - 1060,1290 1440,1060,780

o IT )

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Table 15 . XH NMR S p e c t r a l Data* f o r the Compounds.

Compound N-CH2-N N-CH2-C C-NH-C N- C6H4"N

[Zn2L (N03)4] 3.34(m) 2.43(m) 6.38(m) / .23(m)

[Zn2L8Cl4] 3.36(m) 2.46(m) 6.41(m) 7.28(m)

* C h e m i c a l s h i f t s m "-- mul t i p ] e t

(5 /ppm) w i t h m u l t i p l i c i t i e s i n p a r e n t h e s i s

Table 16. \ieff Values, Ligand Field Bands observed in the Electronic Spectra (cm" ), their Assignments and EPR Spectral Parameters for the Compounds.

Compound n Band position Assignments

(B.M.) (cm"1) g | gj_

[Mn2L*(NO,)4] 5.83 18600 22400

[Mn2L*Cl4] 5.85 18900 22600

[Co2Lg(NO,)4] 4.27 13900

21500

[Co2LKCl4] 4.13 14300

21900

[Ni2L8(NO,)4] 3.11 11200

20000

27500

6A,g -» % g ->

6A,g -> 6A,g ->

4T,g (F) -> 4T,g(F) ->

4T,g(F) - • 4T,g(F) ->

3A2g(F) - • 'A2g(F) -> 3A2g(F) ->

4T,g(P) 4T2g(F)

4T,g(P) 4T2g(F)

4A2g(F) 4T,g(P)

4A2g(F) 4T,g(P)

3T2g 'T,g(F)

3T,g(P)

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Chapter 3 Bis(macrocyclic) Complexes ] uE

in the region 430-470 cm'1 which is assignable to a v(M-N) vibration

further confirm the involvement of the nitrogen in coordination. In

addition to these vibrational bands, two more bands have been

observed in the spectra of the nitrato complexes at around 1060 and

1300 cm ' which may be assigned to the assymmetric and symmetric

stretches vi and v2 of the nitrate group. We conclude that the NO3

group is coordinated in a unidentate manner based on these data and

10

in comparison with similarly bound nitrate groups .

!H NMR spectra (Table 15) of bis(macrocyclic) zinc complexes

recorded in DMSO- d6 show two multiplets in 6.38, 6.41 and 3.34,

3.36 ppm regions which correspond21 22 to the secondary amino (C-

NH-C,8H) and methylene (N-CH2-N,8H) protons, respectively.

Another multiplet observed for both the complexes in the 2.43, 2.46

ppm region may be due to the methylene (N-CH2-C,24H) protons of

the triethylenetetraamine moiety. Another multiplet observed for all

the compounds in the region 7.23 and 7.28 ppm corresponds to the

aromatic ring protons23 and the relative intensity for the biphenyl

protons is expected to show 1:1 ratio. More interestingly, no band is

observed which is assignable to the aldehydic or primary amino

protons which strongly support the concluded ligand frame-work.

Chapter 3 Bis(macrocyclic) Complexes ] [M

The room temperature EPR spectra (Table 16) of the copper(II)

bis(macrocyclic) complexes show a single broad band with two g

values at 2.25. 2.30 and 2.09. 2.14 Gauss, respectively. The absence

of hyperfine splitting signals in these complexes may be due to strong

dipolar and exchange interactions between the copper(II) ions in the

unit cell24. The observed g values indicate25 the presence of an

unpaired electron in the d., , orbital, a phenomenon reported in

many other complexes. The ratio G = (g||-2)/ (gi-2) implies the

possibility of exchange interaction in the copper complexes . When

G > 4. the exchange interaction is negligible and vice versa. In the

present complexes, the value is 2.142 and 2.777 which indicates a

considerable exchange interaction present in these complexes. It has

been reported27 that g|| is a sensitive function for indicating

covalency; for an ionic environment, gp is greater than 2.3 and for a

covalent environment gj is less than 2.3. In the present complexes,

gU < 2.3, is indicative of the covalent nature of the complexes.

The electronic spectra (Table 16) of the manganese complexes

gave two bands in the regions 18600,18900 and 22400,22600 cm"1

which may be assigned28 to 6A l g -> 4T l g(P) and 6A l g -> 4T2g(F)

transitions, respectively, suggesting an octahedral environment

around the manganese(II) ion. However, the spectra of the cobalt

Chapter 3 Bis(macrocyclic) Complexes ] DE

complexes gave two ligand field bands in the regions 13900,14300

and 21500,21900 cm'1 which are assigned to the 4T, , (F) - • 4A3f(F)

and 4Tig(F) -> 4T l g(P) transitions, respectively, consistent with the

octahedral geometry of the cobalt ion. The expected band below

11100 cm"1 could not be recorded as it is beyond the range of the

instrument used. The broad band in the range 11200,11350 cm" and

the two distinct bands in the spectra of the nickel complexes in the

20000,20600 and 27500,27850 cm"1 regions may be attributable

to the 3A2g(F) -> 3T2 g , 3A2g(F) - • 3T l g(F) and 3A2g(F) -+ 3T l g(P)

transitions, respectively. The electonic spectra of the copper

complexes exhibit two bands in the regions 16300,16500 and

19900,20400 cm"1 which unambig-uously may be assigned to the

: B l g -> 2B2 g and 2 B ! g -> 2Eg transitions, respectively, corresponding

to a distorted octahedral geometry of the copper ion. The magnetic

moment values further suggest the proposed geometry. All the

complexes exhibit a high-intensity band around 35000 cm" which

may be due to the charge transfer transition (either metal to ligand,

or ligand to metal). The electronic absorption bands of all the

bis(macrocyclic) binuclear complexes, in comparison with those of

the similar mononuclear complexes reported earlier, do not show

appreciable differences. Furthermore, the magnetic moment values of

Chapter 3 Bis(macrocyclic) Complexes 132

the present complexes agree well with their mononuclear analogues.

This similarity in spectral and magnetic properties suggest that the

metal centres are non-interacting in the present complexes in

solution. However, intermolecular interaction cannot be ruled out in

the solid complexes.

3 References ] run

REFERENCES

S.V. Rosokha, Y D . Lampeka and L.M. Maloshtan, J. Chem. Soc. Daiton Trans., 1993.631.

A. Bilyk and M M . Harding, ./. Chem. Soc. Daiton Trans., 1994, 77.

C. Fraser. R. Ostrander. A.L. Rheingold, C. White and B. Bosnish, Inorg. Chem., 1994, 33, 324.

D.G. McCollum, L. Hall, C. White, R. Ostrander, A. L. Rheingold, J. Whelan and B. Bosnich, Inorg. Chem., 1994, 33, 924.

M. Shakir, S.P. Varkey and O.S.M. Nasman, Polyhedron 1995, 14, 1283.

V.B. Arion, N.V. Gerbelen, V.G. Levitsky, Y. A. Simonov, A. A. Dvorkin and P.N. Bourosh, J. Chem. Soc. Daiton Trans., 1994, 1913.

H.S. Mountford. D.B. MacQueen, A.L. J.W. Otros, M. Calvin, R.B. Frankel and L.O. Spreer, Inorg. Chem., 1994, 33, 1748.

M. Shakir, S.P. Varkey and P.S. Hameed, Polyhedron, 1995, 14, 1355.

M. Shakir and S.P. Varkey, Transition Met. Chem., 1994, 39, 606.

D.E. Fenton, Adv. Inorg. Bioinorg. Mech., 1983, 21, 817.

J.P. Collin, A. Jonaiti and J.P. Sauvage, Inorg. Chem., 1988, 27, 1988.

J.P. Collman, N.H. Hendricks, C. R. Leidener, E. Nagmeni and M.Liter, Inorg. Chem., 1988, 27. 387.

M. Baley, J.P. Collin, R. Ruppert and J.P. Sauvage. J. Am. Chem. Soc, 1986, 108, 7461.

14. L. Fabbrizzi, F. Forlini, A. Perotti and B. Seghi, Inorg. Chem., 1984, 23, 807.

15 E.K. Barefield. D. Chueng, D.G. V. Derveer and F.J. Wagner, J. Chem. Soc Chem. Commun., 1981, 302.

16. A. Buttafare. L. Fabbrizzi, A. Perotti, A. Poggi and B. Seghi, Inorg. Chem., 1984, 23, 3917.

17. M. Cianpolini, M. Micheloni, N. Nardi, F. Vizza, A. Buttafare, L. Fabbrizzi and A. Perotti, J. Chem. Soc. Chem. Commun., 1984, 998.

18. W. J. Geary, Coord. Chem. Rev., 1971, 7, 81 .

19. M. Shakir and S.P. Varkey, Polyhedron 1995, 14, 1117.


21. M. Shakir, S. P. Varkey and P.S. Hameed, J. Chem. Research (M), 1993, 11 ,2969.

22. K. Burgers, D. Lim, K. Kantto and C.Y. Ke, J. Org. Chem., 1995, 59, 2179.

23. M. Shakir and S.P. Varkey, Polyhedron 1 9 9 4 , 1 3 , 9 4 1 .

24. l.S. Ahuja and S. Tripathi, Indain J. Chem., 1991, 30A,1060.

25. B.J. Hathaway and A.A.G. Tomlinson, Coord. Chem. Rev., 1970, 5, 1.

26. I.M. Proctor. B.J. Hathaway and P. Nicholls, J. Chem. Soc, A, 1968, 1678

27. D Kivelson and R. R. Neiman, J. Chem. Phys., 1961, 35,149.

28. A.B.P. Lever. "Inorganic Electronic Spectorscopy", Elsevier, Amsterdam (1984).

Chapter 3 Dithiadiaza Macrocyclic Complexes J [ 135

3.5

SYNTHESIS AND SPECTROSCOPIC STUDIES OF DITHIADIAZA MACROCYCLIC COMPLEXES

3.5.1 INTRODUCTION

The chemistry of macrocyclic compounds is a rapidly

developing research area in view of their various applications' ~,

particularly in the field of catalysis3 4. The metal ion chemistry of

macrocyclic compounds incorporating sulfur and nitrogen or sulfur,

nitrogen and oxygen as donor sites in the ring system have been

studied extensively5"11, but investigation of the effects of

incorporating a soft sulfur donor into a ligand frame-work containing

Chapter 3 Dithiadiaza Macrocyclic Complexes | [ 136|

harder nitrogen atom is of great interest6"12'13. Although sulfides are

generally treated as very poor ligands to transition metal centres ,

recent studies15"17 have proved that macrocyclic sulfides readily bind

to transition metal ions to form stable complexes. It has been noted

that addition of appropriate ring substituents should assist in the pre-

organization of the ligand towards an endo conformation in which the

1 R

lone pairs on the sulfurs are oriented towards the ligand cavity ,

resulting in increased stability constant. In this laboratory, for quite

sometime, we have been engaged in a program aimed at credible

synthesis of macrocyclic complexes10 containing sulfur and nitrogen

donor atoms and in this study we wish to report a new series of

dithiadiaza macrocyclic complexes obtained by the template

condensation of 1, 2-ethanedithiol, o-bromoaniline and succinic or

phthalic acid.


The chemicals o-bromoaniline, 1,2-ethanedithiol (both

Fluka Chemika), succinic acid (Loba Chemie, India), phthalic acid

(S.D. Fine Chemicals, India) were used as received. The metal salts

MX2.6H20 [M = Co" and Ni"; X = CI or N03), CuX2.2H20 [X = CI

Chapter 3 Dithiadiaza Macrocyclic Complexes [ [ 137|

or NO3], Zn(N0.02 and ZnCl2 were BDH quality, available

commercially.

Dichloro/nitrato(l:2,7:8-dibenzo- 10,13- dioxo-3,6-dithia-

9,14-diazacyclotetradecane)metal(II), [ML9X2] [M = Co" or Zn";

X = CI or N0 3 ] and (l:2,7:8-dibenzo-10,13-dioxo-3,6-dithia-9,14-

diazacyclotetradecane)metal(II) chloride/nitrate [ML9]X2 [M =

Ni H or Cu n ; X = CI or NO3].

A mixture of o-bromoaniline (3.44 gm, 20 mmol) and 1,2-

ethanedithiol (0.84 cm3, 10 mmol) in methanol (75 cm3) was taken in

a round bottomed flask and stirred with slight heating for about 35

min. A warm methanolic (50 cm3) solution of the metal salt (10

mmol) was added dropwise followed by the addition of succinic acid

(1.18 gm, 10 mmol) dissolved in MeOH (30 cm3). A brisk colour

change was observed after the addition of metal salt solution. The

resulting mixture was stirred again for 13 hrs. The solid product thus

separated was filtered off, washed several times with methanol then

with ether and dried in vacuo.

Dichloro/nitrato(l:2,7:8,ll:12-tribenzo-10,13-dioxo-3,6-

dithia-9,14-diazacyclotetradecane)metal(II), [ML , 0X2] [M = Co11

or Zn"; X = CI or NO3I and (1:2, 7:8,11:12-tribenzo 10,13 -dioxo-

Chapter 3 Dithiadiaza Macrocyclic Complexes 138

3,6-dithia-9,14-diazacyclotetradecane)metal(II) chloride /nitrate

[M L10] X2 [M = Ni" or Cu11; X = CI or N 0 3 ] .

To a stirred mixture of o-bromoaniline (3.44 gm, 20 mmol) and

1,2-ethanedithiol (0.84 cm3, 10 mmol) in methanol (75 cm3 ) was

added dropwise a warm methanolic (50 cm3 ) solution of metal salt

(10 mmol). This was followed by the addition of phthalic acid (1.66

gm, 10 mmol) dissolved in methanol (30 cm3). A gradual colour

change was observed. The reaction mixture was kept stirring for 13

hrs. and the solid mass was isolated by filtration, washed several

times with methanol and dried in desiccator.


A new series of dithiadiaza transition metal complexes have

been prepared via the condensation reaction of 1,2-

ethanedithiol, o-bromoaniline and succinic or phthalic acid in the

presence of transition metal ions as templates (Scheme 10). Attempts

to prepare metal free ligands in methanol led to oily product, which

could not be isolated and analysed. However, when the condensation

reaction was carried out in the presence of metal ions, solid products

were obtained in good yield (65-85%). The complexes prepared by


\ / ^ N H +

^

M X 2

fa ™ ^

SH SH

OH HO

o s s

X H N |NH

1' " S

L , n = (CH2)2 ; m L10, n = (CH2)2 ; m M = C o u and Z n n

X = CI or N 0 3

(CH2)2

C6H4

L% n = (CH2)2; m L10, n = (CH2)2; m M = Ni n and C u n

(CH2)2

C6H4

Scheme 10

Table 17. % Yield, Colour, Melting point, Molar Conductance and Analytical Data for the Compounds.

Compound % Yield Colour Melting Am Point (cm ft mol ) C <°C)

Found (Calc.)%

H N M CI

[CoL (N03)2] 67 Dark brown 310 21 39. 7 39.9)

3.0 3.3)

10.7 10.3!

10.7 10.9)

12.2 (11.8)

[coi/ci2 : 74 bright brown 319 19 4 4 . 7 4 . 0 5 . 9 1 2 . 5 1 4 . 6 1 3 . 6 4 4 . 3 ) ( 3 . 6 ) ( 5 . 7 ) ( 1 2 . 1 ) ( 1 4 . 3 ) ( 1 3 . 1 1

10 CoL ( N 0 3 ) 2 ] 65

[CoL 1 0 Cl 2 ] 71

Bright brown 309

Blackish brown 327

16 4 5 . 1 ; 4 4 . s :

3 . 3 3 . 0 !

9 . 9 4 . 5 )

9 . 7 ( 1 0 . 0 )

11 . 2 1 0 . 8 '

4 9 . 6 3 . 4 5 . 6 1 1 . 2 1 4 . 2 1 1 . 3 ( 4 9 . 2 ) ( 3 . 3 ) ( 5 . 2 ) ( 1 0 . 9 ) ( 1 3 . 9 ) ( 1 1 . 8 )

[ N i l / ] ( N 0 3 ) 2 65 Blackish brown 312 104 40.2 3.7 10.5 10.4 (39.8) (3.2) (10.2) (10.8;

12.3 (11.9:

[NiL/]Cl2

10

67

[NiL ] (N03)2 72

Dark brown 322

Bright brown 307

98

114

44.7 3.5 6.1 (44.3) (3.7) (5.6)

45.2 ,44.8:

3.3 . 3 . 0 :

9.8 9 . 5 :

12.3 13.8 13.4 (12.0) (14.2) (13.0)

9.6 : 9 . 9 i

11.2 (10.8)

[ N i L 1 0 ] C l 2 76

[CuL9] ( N 0 3 ) 2 79

[ C u L 9 ] C l 2 81

[CuL 1 0 ] (No 3 ) 2 84

[ C u L l 0 ] C l 2 85

[ Z n L 9 ( N 0 3 ) 2 ] 65

[ZnL 9 Cl 2 ] 79

[ Z n L 1 0 ( N O 3 ) 2 ] 75

[ Z n L 1 0 C l 2 ] 68

Dark brown 321

Dim green 323

Dark green 239

Light brown 241

Blackish brown 263

Dim blue 314

Greyish blue 319

Dim blue 325

Bright blue 337

49.6 3.5 (49.2) (3.3)

40.1 3.6 (39.9) (3.2)

44.2 3.2 (43.9) (3.6)

42.7 3.4 (42.2) (3.0)

49.2 3.7 (48.8) (3.3)

39.7 3.0 (39.4) (3.2)

44.2 3.3 (43.8) (3.6)

44.6 3.3 (44.3) (3.0)

48.9 3.5 (48.6) (3.3)

5.5 11.3 (5.2) (10.9)

10.6 11.2 (10.2) (11.6)

5.8 12.7 (5.6) (12.9)

9.7 10.3 (9.4) (10.5)

5.6 12.0 (5.1) (11.7)

10.6 11.4 (10.2) (11.8)

5.6 13.6 (5.2) (13.2)

9.7 11.3 (9.4) (10.9)

5.5 12.4 (5.1) (12.0)

13.6 12.3 (13.2) (11.9)

11.5 (11.7)

14.5 13.3 (14.2) (13.0)

10.3 (10.6)

13.5 11.5 (13.1) (11.8)

12.1 (11.7)

14.5 13.3 (14.1) (12.9)

11.2 (10.7)

13.4 11.4 (13.0) (11.7)

Table 18. IR Spec t ra l Data (cm" ) f o r t h e Compounds.

Compound V(C-H)

I

[CoL 9 (N0 3 ] 2 ]

[CoL 9 Cl 2 ]

[ C o L 1 0 ( N 0 3 ) 2 ]

[CoL 1 0 Cl 2 ]

[ N i L 9 ] ( N 0 3 ) 2

[ N i L 9 ] C l 2

[ N i L 1 0 ] ( N 0 3 ) 2

t N i L 1 0 ] C l 2

[CuL 9 ] ( N 0 3 ) 2

2955

2945

2940

2920

2 8 9 5

2910

2 9 0 5

2920

2 9 3 0

1710

1690

1700

1 7 2 5

1 7 0 5

1 7 1 5

1710

1 7 2 0

1 6 8 5

Amide bands V(M-N)

II I£I IV

1535 1265 650 395

152 0 12 60 655 415

1530 1255 665 420

1520 1260 660 400

1510 1240 645 395

1520 1230 635 400

1530 1235 640 405

1505 1225 650 410

1535 1230 640 395

V(M-S) V(M-C1) Ring vibrations

340 - 1400,1020,720

355 280 1405,1015,725

360 - 1415,1025,735

370 275 1420,1035,740

365 - 1410,1030,730

370 - 1430,1050,720

355 - 1400,1020,750

340 - 1425,1025,735

345 - 1425,1035,740

I D CM

r o n o .—i

o oo M-

o CM

r-o CM

o 1—1

i n C\J

r

IT) L O

r o «a* o 1—1

o o ^T

i n oo r-o r

o i—i

m oo • ^

U0 00

r-o ^T

o I—1

O

oo V

IT) CM

r-m oo o • — 1

m 0 0 <3"

o 0 0

r-U0 CM

o 1—1

o oo *y

c CM

in oo CM

o <=r oo

Ln oo oo

o <X> oo

o T on

c 0", oo

o m n

m T oo

o <3<

m i—i

m o r-H * T

m o T

o o ^

m ^r IX>

oo 00 IX>

o LO \D

m T <X>

O 00 <£>

O

• <X>

m oo >X>

m oo CM

m CM CM

m iX>

CM

m £>

CM

LT,

r-CM

m m CM

O r-CM

o oo m

m i—i

m

m 00 m

o r\j m

oo o 00

o 1—1

m

m tn VX>

o CT^. IX)

o T—1

r-

o CM r~

o in 00 CM

o CM Cft (M

m i—i

CTi CM

m m en CM

o CM

cn CM

OO CM C^, CM

o o CTi CM

o 1—1

(T\ CM

I N

H

u '—' O l

^ 3 U

o 2

. — i

o i - i

^ 3 U

eg .—1

u o ~H

^ 3 u

.—. n

O 2 ~— a-, J C

M

, rg

CJ

o\ .J C N)

m O 2

o , — i

^ C

N]

• H t )

o ,—1

h3 C

Nl

Table 19. 1H NMR S p e c t r a l Data* f o r t h e Compounds

Compound C-NH-CO CO-CH2-CH2-CO S - CH2-C Phenyl r i n g

[ZnL9(N03)2] 8.43(m) 3 . 2 9 ( s ) 3.76(m) 7 .33(m)

[ZnL9 Cl 2 ] 8.36(ra) 3 . 3 3 ( s ) 3.81(m) 7.24(m)

[ZnL10(NO3}2] 8.32 (m) - 3 .78 (m) 7 . 2 1 (m)

[ZnL1 0Cl2] 8.37(m) - 3.87(m) 7.31(m)

^Chemical shifts (5/ppm) with multiplicities in parenthesis s = singlet and m = multiplet

Table 20. \ie{f Values, Ligand Field Bands observed in the Electronic Spectra (cm1), their Assignments and EPR Spectral


Compound K-ff. (B.M.)

Band position

(cm1)

Assignments

g|

EPR data

[CoL9(N03)2]

[CoLTI2]

[CoL,0(NO3)2]

[CoL,0Cl2]

[NiL9](N03)2

[NiL;] Cl2

4.09

4.10

4.08

4.10

16900

21800

16400

21500

16950 21850

16450 21650

16200

20700

15850 19550

g(F g(F

g(F

g(F

g(F g(F

g(F g(F

Aig

Aig

Aig Aig

-> A2g(F)

- • 4Tig(P)

-> A2g(F)

-> 4T|g(P)

-> 4A2g(F)

-> 4T.g(P)

-> 4A2g(F)

-» 4Tig(P)

. 1, B,g A2g

-> 'Big

(N r-<N

r<-i 00 o

I T i l / " j

l/">

1 -T • ^

<N

(N

(N O (N

o ( S

(N (N rsi <N

00 J?

T T oo oo < _ <

00

_CQ

T 00

_<

oo <

t oo <

00 00 — 00 rM

< UJ CQ c>l rN (N

t ! t oo oo oo

CQ CQ CQ <N rsi I N

00 00 — 00 <N

< UJ CQ (N IS IN

t T t oo oo oo

CQ CQ CQ (N fS (N

00 00 — OO <N

< UJ CQ fN rs| fN

t t T oo oo oo

CQ CQ CQ d (N N

oo _„ oo - 50 N

< UJ CQ rJ rsi fN

! I

oo oo oo CQ CQ CQ

IN (N fN

o o o 00 o (N

o o o IT)

o w, >o o

c o (N \ 0

o v/-, r-~

o o I/-)

o o —

o \T\

o o o TT

o v> c->

O o oo

o V i l/~>

o V~>

^-o o r

o ir> rr

oo 00 oc

o z o z o z

-J z

- J 3 3

o -J 3

u

Chapter 3 | [ Dithiadiaza Macrocyclic Complexes 147

the template method have 1:1 metal to ligand stoichiometry. The

molar conductance values (Table 17) of cobalt and zinc complexes

indicate that they are non-electrolytic in nature while other

complexes exhibit19 20 their ionic nature. The overall geometries were

inferred from the various spectroscopic studies discussed below.

The preliminary identification of the synthesized macrocyclic

complexes have been obtained from IR spectra. The main bands and

their assignments are listed in the Table 18. The absence of bands

characteristic of thiol or hydroxyl groups and the appearance of

bands corresponding to an amide group strongly suggests that the

proposed ligand frame-work is formed. The four amide bands

identified in the 1685-1730, 1505-1535, 1225-1275 and 630-665 cm"1

regions may reasonably, be assigned to amide I[v(C=0)], II [v(C-N)

+ S(N-H)], amide III [6(N-H)] and amide IV [<KC=0)] bands,

respectively5. The position of amide I, [v(C=0)] band is in the region

of metal free amide"1 which rules out the possibility of coordination

through amide oxygen. The presence of a sharp band in the region

395-420 cm"1 in all the complexes is due to the v(M-N) vibration22.

Bands in the region 275-290 cm"1 are asssignable to v(M-Cl)

stretching vibrations. A new medium intensity band in the region

330-370 cm"1 may reasonably be assigned to v(M-S). The phenyl ring

Chapter 3 Dithiadiaza Macrocyclic Complexes | | 148|

and other fundamental vibrations23 appeared at their expected

positions.

The ]H NMR spectra (Table 19) of zinc(II) complexes recorded

in DMSO- d6 show two broad signals in the region 8.32-8.43 ppm

which may be assigned to the amide (C-NH-CO,2H) protons24 '25. A

singlet in the region 3.29, 3.33 ppm was observed for the respective

complexes [ZnL9(N03)2] and [ZnL9Cl2], which can be assigned26 to

[CO-(CH2)2 - CO,4H] protons. All the zinc complexes show multiplet

in the region 7.21-7.33 ppm owing to phenyl ring protons21. The 'H

NMR spectra of [ZnL9(N03)2], [ZnL9Cl2], [ZnL10(NO3)2] and

[ZnL Cl2], gave a multiplet in the region 3.76-3.87 ppm

corresponding25 to methylene protons adjacent to sulfur (S-CH2,4H).

However, the absence of thiol or carboxylic protons again further

confirm the proposed frame-work.

The EPR spectra (Table 20) of the polycrystalline samples of

copper(II) complexes were recorded at room temperature and their gj

, gi values have been calculated. The copper(II) hyper-fine line could

not be resolved in any of the complexes at room temperature. This

may be attributed to the strong dipolar and exchange interactions

between copper(II) ions in the unit cell27. A single broad signal with

two g values, consistent with an axial symmetry (g | > g±) in the


molecule, was exihibited. This indicates28 essentially a d , ground

state for the copper(II) ion. All the macrocyclic copper(II) complexes

gave g|| and gj. values in the 2.32-2.37 and 2.09-2.12 range,

respectively. In these complexes gj > 2.3 is indicative of ionic

nature and is well suited for electrolytic nature of copper. In the

axial symmetry the exchange interaction measurements between the

copper centres in the crystalline solids are expressed by Q = (g | . 2)

/(g± - 2). The calculated G values for the complexes appeared in the

range 3.083 to 3.555 which suggest (G < 4)29 a considerable exchange

interaction in these complexes.

The electronic spectra (Table 20) of the complexes derived

from the cobalt(II) showed two bands aroundl6450 and 21650 cm"1

which may reasonably correspond to the 4T l g(F) -» 4A2g(F) and

Tig(F) -> 4T l g(P) transitions, respectively, suggesting an octahedral

geometry for the complexes30. However, the reflectance spectra of the

cobalt complexes exhibited only one band around 15560 cm"1

assigned to the 4A2g(F) -> 4T,g(P) transition, consitent with the

tetrahedral environment of the macrocyclic moiety around the

cobalt(II) species31. The difference in electronic and reflectance

spectral data suggest that there exist different geometries in solution

and solid state.

Chapter 3 Dithiadiaza Macrocyclic Complexes

The macrocyclic complexes of nickel(II) exhibit two bands in

their electronic spectra at around 15900 and 19650 and may be

assigned to !Aig -> 'Big and 'A] g -> 'A^g transitions, respectively,

suggesting a square-planar geometry around the nickel(II) ion.

The electronic spectra of copper(II) complexes showed a broad

band centred at ca. 16200 assignable to B ] g —> A ]g transitions.

However, two weak shoulders appearing around 21700 and

11450 cm"1 may be ascribed to 2B]g -» 2Eg and 2 B ] g ->

'B 2 g transitions, corresponding to a square-planar geometry around

the copper(II) ions.

The magnetic moment values further confirm the above

proposed geometries.

Chapter 3 References ] tm

3.5.4 REFERENCES

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Chapter 3 C References am

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CHAPTER-This chapter concludes the formation, bonding and stereochemistry of newly synthesized complexes.

Chapter 4 1 1 Conclusion | | 15S|

CONCLUSION

r I ^his thesis is a small addition to the coordination

-*- chemistry of transition metal complexes with

multidentate ligands. The main aim behind this study was to

design new macrocyclic ligands and their complexes in view of

their variety of applications. However, an attempt has also been

made to synthesize tin-transition metal heterobimetallic

complexes with a view to provide different environments in the

bimetallic complexes for the metal atoms; one transition (Mn",

Co , Ni", Cu" and Zn") and other non-transition metal have

Chapter 4 Conclusion 156

been choosen for this purpose. The mode of coordination behaviour

of central metal ion is proposed on the basis of available consistent

spectroscopic and physico-chemical data. This project does not

include the various applications, although the synthesis and

characterization of a variety of macrocyclic and heterobimetallic

complexes particularly tetraoxotetraamide, tetraiminetetraamide, bis-

macrocyclic, dithiadiaza and tin-transition metal heterobimetallic

complexes was based on their applications.

The metal templation was the main criterion adopted to

synthesize these complexes. Except in one case, the medium of

reaction was methanol. The attempts to synthesize metal-free

macrocyclic ligands was futile leading to the formation of unstable

oily product, which could not be isolated and analysed. It is an

established fact that templation is an efficient approach to synthesize

macrocyclic complexes with considerable yields without any side

reactions as compared to high dilution technique, which is used to

synthesize complexes from pre-formed ligands. It is, therefore,

concluded that metal ion directs the steric course of the reaction in

the synthesis of macrocyclic complexes to provide better yields.

The complexes obtained were stable to atmosphere in the solid

state and were freely soluble in polar solvents like

Chapter 4 | | Conclusion | | 157

dimethylformamide, dimethylsulphoxide and acetonitrile. The molar

conductance values in DMSO were generally supportive of their non-

electrolytic nature, however, in certain cases complexes of nickel and

copper exhibit their ionic behaviour. The results of spectroscopic

studies, viz. IR, 'H NMR, EPR, electronic spectral and magnetic

susceptibility measurements show that the complexes in general have

octahedral stereochemistries except a few complexes of nickel and

copper which exhibit square-plannar geometries.

synthesis and physico-chemical studies of thesi s · "synthesis and physico-chemical studies...

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