1 msc: f-elements, prof. j.-c. bünzli, 2008. 2 chapter 3 coordination chemistry 3.1properties of...

1MSc: f-Elements, Prof. J.-C. Bünzli, 2008


Chapter 3 Coordination chemistryChapter 3 Coordination chemistry

3.1 Properties of aqueous solutions (4f ions)3.2 Properties of non-aqueous solutions (4f ions)3.3 Properties of aqueous solutions (5f ions)3.4 Macrocyclic complexes

3.4.1 General principles3.4.2 4f complexes3.4.3 Some 5f complexes


3.1 Properties of aqueous solutions (4f ions)

Co-ordination numbers in water

• In the solid state, CN = 9 from La-Lu as shown by the X-ray structures of bromates and ethylsulfates

• In solution, 8 or 9? Change along the series or not?

• Kinetic studies, optical data, NMR data, X-ray diffraction data ,neutron diffraction data:

The CN changes from 9 (La-Nd) to 8 (Dy-Lu)with an intermediate number for Sm-Tb (equilibria)

Chapter 3 Coordination chemistry


9

8

equilibria

0.80 0.85 0.90 0.95 1.007

8

9

10

7

8

9

10

Eu

Lu

La

(ri)-1/(Å)

-1, CN = 9

CN

Rizkalla & Choppin, Handbook on the Physics and Chemistry ofRare Earths, Vol. 15, Ch. 103 (1991).



Hydration enthalpy

0.80 0.85 0.90 0.95 1.00

3300

3400

3500

3600

3700

3800

[Ln(H2O)x]3+

(r)-1/Å-1 (CN=9)

CaII: -1585 kJmol-1

-Hohydr/kJmol-1



Hydrolysis

m [Ln(H2O)x]3+ [Lnm(OH)l(H2O)(n-l)](3m-l)+ + l H+

[Lnm(OH)l (H2O)(n-l ) ](3m-l)+[H+]l

[Ln(H2O)n3+]m

*l,m =

Example Ligand L, LogK1 = 3, pH = 7, Log*11 = -8[L]free = 10-3 M[LnL] : [LnOH] : [Lnaq] = 45 : 45 : 10 %



56 58 60 62 64 66 68 70 72

-9.0

-8.8

-8.6

-8.4

-8.2

-8.0

Z

LnIII hydrolysis

298 K, I = 0.3 M

Lu

Gd

La

Log*11



0.80 0.85 0.90 0.95 1.005.5

6.0

6.5

7.0

7.5

0.80 0.85 0.90 0.95 1.00

5.5

6.0

6.5

7.0

7.5La

CePr

NdSmEuGd

TbDyHoEr

TmYb

LuHydroxide precipitation pH at 298 K

pH

(r)-1/Å-1 (CN=9)



Kinetic aspects

LnIII ions are very labile in water

[Ln(H2O)x]3+ + H2O [Ln(H2O)x-1(H2O)]3+ + H2O

kex for water exchange is in the range 107-109 s-1

It has been measured by:

• EPR (Gd)

• NMR (17O and longitudinal 1/T1 and transverse 1/T2

relaxation times)

• Ultrasonic absorption spectroscopy



D. P. Fay et al., J. Phys. Chem. 1969, 73, 544

[Ln(H2O)x]3+ + SO42-

[Ln(H2O)x-1(SO4)]+ + H2O

0.80 0.84 0.88 0.92 0.967.6

7.8

8.0

8.2

8.4

8.6

8.8

9.0

9.2

La

Ce P

r Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lulo

gk d

iss (298 K

)

r-1 (CN=9) /Å-1



0.90 0.91 0.92 0.93 0.94 0.95 0.96 0.97

7.6

7.8

8.0

8.2

8.4

8.6

8.8

9.0

r-1 (CN=9) /Å-1

[Ln(H2O)x]3+ + H2O [Ln(H2O)x-1(H2O)]3+ + H2O

Ia

Log

kex(2

98 K

)Chapter 3 Coordination chemistry


3.2 Properties of non-aqueous solutions (4f ions)

Acetonitrile

Most counterions are coordinated, at least partially.The solvation has been studied either by NMR or byvibrational spectroscopy (IR/Raman).

Anhydrous perchlorates:

Presence of [Ln(MeCN)x]3+

[Ln(ClO4)(MeCN)x-2]2+

[Ln(ClO4)2(MeCN)x-3]+

Bis (perchlorato) species:La 25 %, Pr 10 %, Tb-Lu 0 %



0.80 0.85 0.90 0.950.50

0.75

1.00

1.25

1.50

1.75

2.00

0.50

0.75

1.00

1.25

1.50

1.75

2.00

nc (C

lO4)

Number of coordinated ClO4-

ions per LnIII ion

La

Pr

Sm

Eu

Gd

Dy

Tb Yb

Nd

Tm

r-1 (CN=9) /Å-1



LogK ’s in acetonitrile

LogK1(ClO4-) LogK3(SO3CF3

-)

Tb 1.9 ± 0.4 2.5

Dy 1.8 ± 0.4 2.6

Ho 1.8 ± 0.3 2.5

Er 2.1 ± 0.4 2.5

Tm 2.7 ± 0.5 2.4

Lu 2.4 ± 0.4 2.3

Di Bernardo et al.Inorg. Chim. Acta1993, 207, 85

Bünzli, Milicic-Tang, Handbook on the Physics and Chemistry ofRare Earths, Vol. 21, Ch. 145 (1995)



0.80 0.85 0.90 0.95 1.006

7

8

9

10

6

7

8

9

10

R = 15

R = 8

Ln(ClO4)3 + R DMSO in MeCN

(ri)-1 / (Å)-1, CN = 9

La

Lu

Perchlorates in presence of dimethylsulfoxide



0.960.970.980.991.001.011.021.036.46.66.87.07.27.47.67.88.08.2

Tb

Dy

Ho

Er

Tm

Yb

Log

kex(2

98 K

)

r-1 (CN=9) /Å-1

Change ofmechanismfrom D toID

Kinetic aspects

[Ln(dmf)8]3+ + dmf [Ln(dmf)7 (dmf)]3+



Id mechanism

Dissociative mechanism D

Activation thermodynamic parametersActivation volume



3.3 Properties of aqueous solutions (5f ions)

Far less data than for Ln ions, and many of them areextrapolated from Ln data.

A trend similar to Ln seems to prevail for An3+:

Am CN = 9.0 Eu CN = 8.3Cm 8.9 Gd 8.2Cf 8.2 Dy 8.0Es 8.0 Ho 7.9

Hydration numbers (first + second coordination spheres)are between 14 and 16

Hydrolysis is also important with Log*11 values between-3.8 for Fm(OH)2+ to -7.4 for Np(OH)2+



Dioxo actinide cations AnO22+

Uranyl solutions contain polymeric species at pH > 2:

[UO2(OH)]+ Log*11 = -5.72[UO2(OH)2] Log*12 = -11.78[(UO2)2(OH)2]2+ Log*22 = -5.89

pH values required to achieve 50 % dimerization:

[AnO2]2+t UO2

2+ NpO22+ PuO2

2+

0.1 M 3.45 3.84 4.76 0.01 M 4.46 4.94 5.87 0.001 M 5.56 6.54 7.51



3.4 Macrocyclic complexes

3.4.1 General principles

Historical outlook

1955-1970Discovery of nonactin (1955), a natural antibiotic

O OO

O Me

Me

OO O

OMe

MeO

O

Me

OO

Me

Me

Me

nonactin



Natural ionophores

• Substances with the ability of transferring an ion from an aqueous phase into a hydrophobic phase

• Essential components of the transport of alkali cation though biological membranes

• 1967: crystal structure of the potassium-nonactin complex

Globular complex with a polar cavity and an externalhydrophobic envelope elegant way to achieve lipidsolubility of cations



C.J. Pedersen, 1967

Serendipity helpsthe discovery ofcrown ethers!

OH

OH

O

Cl

Cl

+

OH

O

O

O

HO

O

O O

O

1 2 -cro w n -41 2 C 4

O

OO

O

O

1 5 -c ro w n -51 5 C 5

O

O

O

OO

O

1 8 -c ro w n -61 8 C 6

b e n zo -1 5 -cro w n -5B 1 5 C 5

O

OO

O

O

d ib e n zo -1 8 -c ro w n -6B 2 1 8 C 6

O

O

O

OO

O

targeted molecule

isolated molecule

La, Ce complexes



J.-M. Lehn, 1969cryptands

N

O O

O

N

OO

O

(2.2.2)

O

N

O

OO

N

O

(2.2.1)(1.1.1)

O

N

O N

O

Porphyrins andphthalocyaninesMid 1965’s

H

N

N

N

N

HRR

R

R

R1

R2 R3

R4

R5

R6R7

R8

Porphyrin

H

N

N

N

N

N

N

N

N

H

Phthalocyanine



Schiff bases, late 1970’s

D

N N

R

D

N

N

R

D

N

N

R

1970-1990

[1+1]

[2+2]

D

O O

+

H2N R NH2

D = N, O, (S)



+NaOH

Calix[n]arenes (Gutsche 1970)

OH HOOHOH

n=4



R R R

R

OHOHOH

OH

wider rim(upper rim)

narrower rim(lower rim)

coneconformation

partial cone

1,3-alternate1,2-alternate



The lock and key principle (E. Fischer, 1894)

++ ++

Pre-organizedReceptor(host)

Pre-organizedReceptor(host)

potentialguestspotentialguests Host-guest complexHost-guest complex

GGrr << GGrr ,, GGrr



• Steric complementarity• Interaction matching (HSAB principle)• Maximizing the number of interaction sites • Maximizing bonding strength

Cation recognition:Size (spherical cations)Stereochemistry (e.g. d-elements)

N+

H

HH

HO

ON

N

O

O

N

NO

OO

ON

N

O

O

N

NO

ON+

H

HH

H



The induced fit concept (Koshland 1958)

Predisposed receptors

flexibility

Finer recognitionClasses of ligands:

- large flexible macrocycles- macrocycles fitted with pendant arms



3.4.2 4f Complexes

For LnIII ions, this principle is difficult to use becausethey are spherical, hard ions with similar properties

Small differences in hardness and sizeDifficult to match the large coordination numbers (8-12)

ri 0.18Å

La Lu

ri 0.015 Å

A. The lock and key principle



LnIII ions and 18C6 ether and Me2(2.2)

[Nd(NO3)2(18C6)]+ [Eu(NO3)2Me2(2.2)]+

O

N

O O

O

NMe Me

O

O

O

OO

O



Some discrimination between larger and smaller ions



Ln(CF3SO3)3 in propylene carbonate

Effect of the donor atom

O

N

O O

O

NH H

OO

O

OOO O

OO

O

O

HN

OO

N

O

H



Rigidifying the ligand induces more discrimination

O

OO

O

O

O

OO

O

O



Simple cryptands

[Pr(2.2.1)(-OH)2Pr(2.2.1)]4+

[Eu(ClO4)(2.2.2)]2+

The receptors are less rigidthan initially planned!The receptors are less rigidthan initially planned!



Stability constants with (2.2.1): solvent influence

dmso < dmf < H2O << MeOH < AN << PC

Thermodynamicconsiderations showthe « recognition » beingmade by the solventand not by the receptor!

Thermodynamicconsiderations showthe « recognition » beingmade by the solventand not by the receptor!

Much smaller stability than edta complexes!

La Pr Sm Eu Gd Dy Er Tm Yb

6

8

10

12

14

16

18

20

water

methanol

propylene carbonate

Log

K1



Stability constants (Ln(CF3SO3)3 in propylene carbonate)

La Pr Sm Eu Gd Dy Er Tm Yb14

15

16

17

18

19

20

(2,2,1)

(2,2,2)

(2,1,1)

Log

K1

Bestreceptorfor LnIII

ions



Bioanalytical applications

- immunoassays with (bpy.bpy.bpy) cryptate as stain

NN

N NN

NN

N

N

Me MeMe

Lbpy

NN

N NN

NN

N

N

Me MeMe

Lbpy

- pH sensor (with ClO4-)

[EuCl3(H2Lbpy)]2+

At pH < 7, H2L2+

(amine chain)

At pH = 7, HL+

At pH > 7, L amine chain coordinates and expels H2O



Me

N

N

-O

O O

Me

N

N

O-

O O

Large macrocycles

may be flexible enough

to wrap around metal ions

as demonstrated by

this ditopic Schiff base

ligand

B. The induced fit principlea) Large macrocycles



p-tert-butylcalix[8]areneH8bCx[8]

Undulated conformation

In presence of a weakbase, KCO3, formation of1:1 complexes withLn(NO3)3

In presence of a strongerbase, Et3N, formation of 2:1 bimetallic complexes

Large calixarenes



[Eu(NO3)(H6bCx[8])(dmf)4][Eu2(H2bCx[8])(dmf)5]

8-coordination:distorted squareantiprism

Eu-Eu : 369 pm



[Eu2(HbCx[4])2(dmf)4]

The smaller unsubstituted calixarenes are not well suited for LnIII coordination:

[Eu2(H2bCx[5])2(dmso)4]


H4bCx[4] H5bCx[5]


[Eu(OH)(H4bCx[6])(dmf)4]

[Eu2(H2bCx[8])(dmso)4]


H6bCx[6]

H8bCx[8]


Calix[8]arene: mechanistic study of the transformationof the 1:1 complex into the 2:1 complex

[Eu(b-H6L)(NO3)(dmf)4]

[Eu(b-H6L)(dmf)4]+ NO3-

Et3N

[Eu(b-H5L)(dmf)4] + Et4NH+ NO3-

Et3N

K’’ K’K

b-H8L + Eu(NO3)3(dmso)x

K2CO3

[Eu2(b-H2L)(dmf)5]

Eu(NO3)3

Et3N

dmf

Eu(NO3)3

Et3N

dmf

A A’

dmf known

to be proven

J.-C. Bünzli et al., PCCP2005, 2191.



2:1 1:1?

0.15

0.55

0.95 -logR’

A

0.015

0.055

0.095

0.115

576 577 578 579 nm

2:1 1:1



0.03

0.06

0.09

0.00

0.12

825 785 745 705 cm-1

NO3(i)

2 NO3(i)

4

A

NO3(b)

6NO3(b)

3

bound dmf

IR spectrum of a solution of 1:1 complex in dmf



1746 m/z1744174217401738

Positive mode

1296 1298 1300 m/z

Negative mode

[Eu(b-H6L)(dmf)4]+

(b-HL7)-

ES-MS spectra

calculated spectrum



Temperature, pressure dependence of electronic spectra

1:1 2:1

intermediates

O O

HOOH

EuOO

N OO O

HOOH

EuOO

N OO O

HOOH

EuOO

N O

A’

O O

HOO

EuO O

HO EuO O

HO Eu

O O

HOO

Eu Eu

OO

OHO

O O

HOO

Eu Eu

OO

OHO

A

O O

HOOH

Eu +

O O

HOOH

Eu +

O O

HOOH

Eu ++

K =410-5 M K =310-4 M K 8



NN

N N

++

NN

N N

b) Ligands with pendant arms

• Derivatized coronands• Cyclen derivatives• Derivatized calixarenes



• Lariat ethersBibracchial lariat coronand

O

O

O

N

OCH3

MeO12C4NNN

O O

O

N OH

N

HO

O

ON

O

N

CO2H

CO2H

O

N

O

O

O

N

CO2H

HO2C

(2.1)DA (2.2)DA

H218C6sdib



LaCe PrNd SmEuGdTbDyHoErTmYbLu6

7

8

9

10

11

12

13

(2.1)DA (2.2)DA (2.2.1)L

og

K1

Stability constants in water (298 K)

Induced fit versus lock-and-key principle !Induced fit versus lock-and-key principle !



NN

O O

O

N OH

N

HO

H218C6sdib

M. González Lorenzo, J.-C. G. Bünzli et al., Inorg. Chem., 2003, 6946

NdIII sensitization



• Cyclen derivatives

NN

N N

R

R

R

R

R = H cyclenR = CO2H H4dota


[Gd(dota)(H2O)]-

Contrastagent,Guerbet SA1988see Ch. 5.8

H4dota wassynthesized by H. Stetterin 1976

NN

N N O

R

O R

O

R

OR

R = NHMe dtma NH2 tcmc

[La(Otf)(EtOH)(tcmc)]2+

Cleavage ofphosphodiesterbridges in rna


[Tb(L1)(H2O)]3+


• Cyclen derivativesO

RH N

O

O

N HR

NN

N N

RH N

O N H R

C O

C O

R =

L1 L2

Chromophoricgroups for sensitizingthe Ln luminescence



• Cyclen derivatives

10

0

20

30 E/103 cm-1

Eu

5D0

7F

Tb

5D4

F7

The ligand 3*state is ofteninvolved in theenergy transfer

21

25

O

O



0

5

10

15

20

25

Sm

0.4

Eu

5.5

Dy

0.05

Tb

23

L2

Sm

0.7

Eu

25

Tb

1.0

Quantum yields(%) in aeratedwater

L1


HOHOOH HO

-O3S SO3-SO3

--O3S

• Extended systems with calixarenes

Taking advantage of the cone conformation and of strongintermolecular interactions:

Crystal packing of p-sulfonato-calix[4]arene

charged groups

H-bond potentiality

Na5[La(L2)(C5H5NO)2]



A. Drljaca et al., Chem. Commun.1999, 1135

O

O

O

OO

O

HOHOOH HO

HO3S SO3HSO3-O2S

-O

La3+

H2O OH2

OH2

+



Micelle-like edifices can begenerated:

OHOH HOOH

SO2O2S SO3-

-O

[Ln(H2O)7]1/3+

-O

[Ln(H2O)7]3+

-O3S

[Ln(H2O)7]3+

HOHOOH HO

O2S SO2SO3--O3S

-O O-

[(H2O)7Ln]1/3+

O

O

O

OO

O

Here crown-6-ether ismaintained in the cavitythrough H-bonds with water moleculesbound to Ln3+

M. J. Hardie, Chem. Commun.2000, 849



N

O

CH3H3C

O

H2N NH2

2

2+

+ La(ClO4)3(H2O)x

NH3C CH3

N N

NH3C CH3

N NLa

OH2

H2O

3+

EtOH, 1h

(ClO4-)3

Backer-Dirks, 1979[La(NO3)3L]

C. The template effect

Radecka-Parizek 1980



OO OH

CH3

3

N

H2NNH2

NH2

2 + + Ln(NO3)3(H2O)x

EtOH, 12h

NO3

Ln

OH

N

N N

N

OHNN

N

OHN

CH3

CH3

2+

(NO3-)2

C. Platas-Iglesias, 1999



D. Porphyrins and phthalocyanines

NH

NH

NH

NH

R R

R R

R

R

R

R

porphyrinogen (R8H4Pg)

H

N

N

N

N

HRR

R

R

R1

R2 R3

R4

R5

R6R7

R8

porphyrin (H2Por)

H

N

N

N

N

N

N

N

N

H

phtalocyanine (H2Pc)

N

NN

N

N R

R

H

texaphyrin (HTx)



triple deckerdouble decker

Stoichiometries evidenced for Ln complexes:

LL

L

L

1:1 1:2

L

L

2:2 2:3



J. W. Buchler, 1986

Octaethyl-porphyrin Et8Por2-

[CeIV(Et8Por)2][(CeIII)3(Et8Por)2]



Chirality transcription (memory effect)

Double-decker CeIV

porphyrinate

S. Shinkai et al.Perkin Trans. I, 1999, 3259



N

N

N

N

Ce

N

N

N

N

Ce

Racemate mixture= Ph(OMe)= Ph(OMe)22



N

N

N

N

Ce

N

N

N

N

Ce

COOHCO

OHBlocked

conformation

chiralchiralguestguest

C C

OH

O O

OH



COOH

CO

OH

N

N

N

N

Ce

N

N

N

N

Ce

COOH

CO

OH

COOH

CO

OH

Optically active diastereomerFacilitated fixationof second guest



N

N

N

N

Ce

COOH

CO

OH

COOH

CO

OH

Guest removal : residual enantiomeric excess (3 h at RT1 year at -37 oC)

N

N

N

N

Ce



Activation of small molecules

N22-

N-N = 1.234(8) Å

Dinitrogen activation

E. Campazzi et al. 1998

Octaetylporphyrinogen

No loss of N2 under vacuum

NH

NH

NH

NH

R R

R R

R

R

R

R

porphyrinogen (R8H4Pg)

Works also with C2H4 and C2H2



Medical applications: Texaphyrins

John Sessler, Texas A&M University, 1993

N

NN

N

N R

R

H

R'

R'

H

H

N

NN

N

N R

R

R'

R'

X

Ln

X

LnX3 ·nH2O

Et3N, MeOH, air



N

NN

N

NO

O

H

OH

OH

OH

OH

texaphyrin (HTex1)

[Gd(NO3) (MeOH)2(Tex1)]+



N

NN

N

NO

O

H

OH

OH

OO

O

OO

O

texaphyrin (HTex2)

GdTex2: enhancing agent for radiotherapy sizeable relaxivity: non-invasive localization in tissues

LuTex2: photodynamic therapy (Cancer therapy, photoangioplasty, age-related macular degeneration)

J. L. Sessler et al.Prog. Inorg. Chem. 2001,49, 551.



O

O O

O O

ON

Fe

N Fe

N

FeO

O

Fe N

D = 1.20 Å D = 1.20 Å

12-crown-4 12-MCFeNshi-4

O-

O-

NO-

shi3-

E. Metallacycles

Exclusive use of hetero-atoms to generate the receptor



NO

NH

OH

+ 5 Cu(OAc)2 + Eu(NO3)35dmf

1h

H2picha

N

ON

O

Cu

N

O

N O

Cu

NO

NO Cu

N

ON

O

Cu

N

O

NO

Cu

dmf

dmf

dmf

dmf

Eu(NO3)2

+

[Eu(NO3)2(15MCCu(II)Npicha-5)]+



54-membered ringTb(NO3)3

PdII-metallacalix[4]areneencapsulated GdIII



3.4.3 Some 5f complexes

a) Crown ethers Most of the complexes show the receptor being not coordinated if coordinating anions are used.

[Na(18C6)-UO2Cl4-Na(18C6)]

J.A. Danis et al., Inorg. Chem.2001, 40, 3389

Here Na+ binds 18C6better than UO2

2+



[UO2(2.2)](trif)2

[UO2(DC18C6)](ClO4)2

A. Navaza et al.Polyhedron 1984,3, 143.

P. Thuery et al.Acta Cryst. C 1995,51, 801.



b) Calixarenes

Uranium forms very often polymetallic species, exceptwith very small calixarenes.

[UO2L]-

pseudo trigonal

OO

O

OH

OH

HO

H3L



P. Thuéry et al., Polyhedron2003, 22, 3499

[(UO2)4O4(H8L)](solv)

Homocalix[8]arene, HL8

D2d symmetry



J. M. Harrowfield et al.,J.C.S. Dalton Trans. 1991, 2025

[Th4(HL)(H2L)(dmso)4(OH)3(H2O)

p-tert-butylcalix[8]arene



c) Calix-crowns for selective extraction

O O

O

O O OO

O RR

R = CO2H

% extraction (H2O to CHCl3

at pH 8.9, 298 K)

Mg Ca Sr Ba Ra<0.1 16 73 99 >99.9

High selectivity for Ra2+ overthe lighter alkaline-earth metalions.High kinetic stability of theRa2+ complex.

X. Chen et al., Inorg. Chem.1999, 38, 5449



G. S. Girolami et al., Inorg. Chem.1987, 26, 343

d) Porphyrins

[UIVCl2TPP(thf)]


1 msc: f-elements, prof. j.-c. bünzli, 2008. 2 chapter 3 coordination chemistry 3.1properties of...

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