Indian Journal of Chemistry Vol. 39A, November 2000, pp. 1182-1186

Synthesis and characterization of iron (II, III) complexes of 3-hydroxy-benzaldehyde

isonicotinic acid hydrazone

P Mallikarjuna Reddy", K Ani! Kumarb, K Mohan Rajuc & N Manohara Murthy·

Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, India

Received 25 Janumy 2000; revised 17 August 2000

Fe(II) and Fe(lll) complexes of 3-hydroxybenzaldehyde isonicotinic acid hydrazone (3-HBINAH) have been synthesized and characterized by elemental analyses, magnetic susceptibility, electronic, IR, ESR, Mossbauer and XRD studies. The IR spectral studies indicate that nitrogen of azomethine and the oxygen of carbonyl group of the ligand participate in coordination in both the complexes while giving no evidence for the presence of lattice, or coordinated water. The presence of unidentate sulphate, (NH4t ion in iron(II) complex and Fe-CI bonds in iron(lll) complex are al so indicated. The Mossbauer, electronic and electron spin resonance spectral studies and magnetic susceptibility measurements suggest octahedral geometry probably with a slight distortion to both the complexes. The X-ray powder diffraction data indicate that both the Fe(II) and Fe(lll) complexes belong to the tetragonal crystal systems.

Literature survey indicates that there are only quite a

few scattered examples of iron complexes with

isonicotinic acid hydrazones that have been prepared

and studiedH, inspite of the academic, commercial

and the pharmacological prominence of metal

complexes of isonicotinic acid hydrazones. In view of

the importance of iron and isonicotinic acid

hydrazones, we undertook a detailed study of

synthesis and characterization of iron (II, III)

complexes of isonicotinic acid hydrazones derived

from some substituted benzaldehydes. The present

paper deals with the studies carried out on the

synthesis and solid state characterization of iron(ll,

Ill) complexes of 3-hydroxybenzaldehyde isonicotinic

acid hydrazone.

•Department of Physics, V R College, Nellore, 524 00 I, India; hDepartment of Physics, Narayana Engineering College, Nellore, 524 003, India; c Department of Polymer Science & Technology, Sri Krishnadevaraya University, Anantapur 515 003, India.

Experimental Preparation of 3-hydroxybenzaldehyde isonicotinic acid hydrazone (3-HB/NAH)

The method of preparation of 3-hydroxybenzalde­hyde isonicotinic acid hydrazone is similar to that followed by Sah and Peoples3 for the preparation of salicylaldehyde isonicotinic acid hydrazone.

Isonicotinic acid hydrazone (I 0 g) dissolved in I 00 ml of distilled water was mixed with I 00 ml of methanol in which 3-hydroxybenzaldehyde (9 g) was dissolved in a 500 ml round bottom flask. A few drops of I 0% NaOH solution were added to the mixture as a catalyst and the flask was shaken vigorously. The hydrazone formed was filtered off and dried. It was then recrystallized from methanol in the. presence of norit, yield: 94%.

Preparation of iron(!/) complex of 3-HB/NAH Ferrous ammonium sulphate (3.82 g) dissolved in

I 00 ml of distilled water containing a minimum amount of sulphuric acid and an equal quantity of methanol were mixed in a I L round bottom flask and heated on a water bath. 3-hydroxybenzaldehyde isonicotinic acid hydrazone (2.41 g) dissolved in I 00 ml of DMF was added to the hot solution in the flask. Upon mixing, the solution turned yellow and became turbid after I 0 min of heating. The mixture was refluxed for 3 h and 30 min when a chocolate coloured precipitate got settled at the bottom. The solution was cooled and filtered by suction. The residue was washed with water and DMF several times and dried in vacuo.

Preparation ofiron(lll) complex of3-HBINAH Anhydrous ferric chloride (3.24 g) dissolved in I 00

ml of water containing a small quantity of hydrochloric acid was added and I 00 ml of methanol were mixed in a I L round bottom flask. 3-Hydroxybenzaldehyde isonicotinic acid hydrazone (2.41 g) dissolved in I 00 ml of DMF was added to the hot contents of the flask. After a few minutes of mixing, the solution attained black colour with greenish tinge. After 5 h of continuous refluxing, the solution appeared viscous with its colour turned to blood red. The flask was cooled and the contents filtered by suction and the product was washed with

NOTES 1183

water and DMF. The blood red coloured complex thus obtained was dried in vawo.

The metal salts and solvents used in the preparation of the complexes were of AR grade.

The micro analyses of the ligand and complexes were carried out using Carlo Erba I I 06, Thomas CH analyser and Coleman N analyser. Electronic spectra were measured with a arion-cary model 2390 spectrophotometer. IR spectra were obtained in the range 200-4000 cm-1 on a Pye-Unicon SP 2000 model double beam spectrophotometer in KBr discs. 1H NMR spectrum of the ligand was recorded in DMSO medium on a Varian XL-I 00 MHz spectrophotometer at room temperature. Magnetic susceptibility measurements were made using a vibrating sample magnetometer (VSM) operating at a field strength of 0.3 to 0.8 T. Mossbauer absorption spectra of the complexes were obtained at room temperature using ECIL MBS-35 spectrometer operating on multiscalar mode in conjunction with 1024 multichannel analyser. The ESR spectra were recorded on a Varian E-line E-112 X-band (- 9.3 GHz) spectrometer with I 00 kHz modulation. The powder diffraction pattern of the complexes were recorded at 298.15 K on a Philips PW 1140 X-ray diffractometer equipped with iron target. The iron content of the complexes dissolved in dilute HCI was determined using Varian AA-6 single beam atomic absorption spectrophotometer. The high resolution 11C NMR spectra of the complexes in solid state were recorded on JEOL-MN-SN 200 spectrometer.

Results and discussion 3-Hydroxybenzaldehyde isonicotm1c acid

hydrazone is characterized on the basi s of elemental analysis, UV-visible, infrared and 1H NMR spectral data. Analysis: [C = 64.42, H = 4.58, N = 17.41 % ; Required for CuH 11 N30 2 : C = 64.72, H = 4 .60, N = 17.40%], m.pt. 268-269°C.

The UV-vi sible spectrum of 3-hydroxybenzalde­hyde isonicotinic acid hydrazone shows a shoulder at 45454 cm- 1 which may be attributed to rc- rc transitions in the azomethine. Another shoulder is found at 4000 cm- 1 which indicates that the benzenoid ring is a disubstituted one with one of the two functional groups in meta posi tion. The n ~ cr* transitions in the pyridine ring also occur in the same region. The bands observed at 33783 cm- 1, 29671 cm- 1 and 27472 cm- 1 indicate the attachment

~ * of auxochrome to the phenyl nucl eus , n ~ cr

transition5 and lengthening of the rc-system due to interaction of aromatic ring6 respectively.

The IR spectrum of 3-hydroxybenzaldehyde

isonicotinic acid hydrazone shows bands at 3400 cm-1

for N-H; 1645 cm-1 for C=O; 1600 cm- 1 for C=N, and 3190 for phenolic OH group. The I ,3-disubstitution pattern of the phenyl nucleus is represented by the peak appearing at 775 cm-1-4. These data indicate that isonicottmc acid hydrazone has undergone condensation with 3-hydroxy-benzaldehyde.

In the 1H NMR spectrum of 3-hydroxybenzalde­hyde isonicotinic acid hydrazone two broad singlets

appear at 8 12.03 and 9.70 ppm, the integral heights of which represent one proton each, belong to the hydrogen atom of the amide group7 and proton of the hydroxy group attached to the phenyl nucleus4

. The

sharp peak appearing at 8 8.44 ppm corresponds to =CH of azomethine group8

. The two doublets around

8 8.83 and 7.87 ppm are assigned to the four protons

of the pyridine ring system9. The three doublets at 8

7.36, 7.25 and 7.16 ppm and the multiplet at 8 6.90 ppm indicate the four protons attached to the phenyl nucleus9

. The proton flanked between the hydroxyl and azomethine groups is indicated by the doublet at

8 7.25 ppm and J value, 2 Hz, marks meta coupling.

The multiplet around 8 6.90 ppm corresponds to the fourth proton of phenyl nucleus .

The analytical data corresponding to the elemental analysis of iron(II) complex of 3-hydroxybenzalde­hyde iosnicotinic acid hydrazone are given: [Found (calcd), % are C = 41.36 (40.73), H = 4.21 (3 .91 ), N = 14.7 ( 14.62), Fe= 7.26 (7 .3 1 ), anion 26.12 (25 .06)]. For iron(III) complex of 3-hydroxy-benzaldehyde isonicotinic acid hydrazone the data [C = 38.60 (39.46), H = 4.13 (4.06), N = 8.79 (8.98), Fe = 12.0 I ( 11.96), anion = 22.54 (22.75)] . The formulae weights of the complexes evaluated from density, cell volume and the elemental analyses data for Fe(II) and Fe(lll) complexes of 3-hydroxy-benzaldehyde isonicotinic acid hydrazone respectively are 753 (766) and 459 (468). All the analyses of Fe(III) complex are consistent with the proposed formula weight [FeLCI2 (MeOH) 2]CI while that of Fe(II) complex differ with respect to carbon and hydrogen of the suggested molecular formula , [FeL2(S04)2](NH4h The percentages of tron . nitrogen and anion present in the Fe(II) complex full y favour the formula suggested for the complex. Inconsistenc ies of this nature are not uncommon with

1184 INDIAN 1 CHEM, SEC. A, NOVEMBER 2000

inorganic complexes 1. In view of the above discrepancy, the mass spectrum of Fe( II) complex has been obtained by fast atom bombardment mass spectrometer available at Mass Spectrometry Service Laboratory, Nebraska University, USA. The mass spectrum of the complex contains a peak due to the molecular ion (M-H)- in the negative ion spectra 10 at M/z 765 . This value is well in agreement with the value derived on the basis of estimated iron, nitrogen and anion percentages and also with the value evaluated by density and unit cell volume measurements, thereby indicating that the formula suggested is correct. The above data indicate I :2 (metal:ligand) stiochiometry for iron(III) complex. The molecular formulae of the complexes are [FeL2(S04h](NH4)2 and [FeLCI2(MeOH)2]CI respectively where L is 3-hydroxybenzaldehyde isonicotinic acid hydrazone.

The important electronic absorption bands in the spectra of the complexes and the ligand recorded in solid state (mull form) are discussed. The Fe(Il) complex exhibits bands at 45454, 38461 and 33333 cm-1 which are considered to be due to intraligand transitions. The two charge-transfer bands appearing in the region 19000-23000 em_, and the small sharp d-d band due to 5T2M ---7

5EM transitions near 1317 em_,

suggest high spin octahedral geometry for Fe(II) complex of 3-hydroxybenzaldehyde isonicotinic acid hydrazone. These assignments are also in tune with those reported by Lobana et al.10 for high spin octahedral iron(II) systems. The Fe(III) complex shows a sharp band at 49019 em_, corresponding to charge-transfer processes which are of high quantum energy. A broad band observed at 26666 cm-1 is due to T2K - n· transitions. A shoulder and a band appearing at 16666 and 12658 cm-1 are considered to

6 4 d6A 4T ·· be due to A1g ---7 T2x an Ix ---7 Ig transitions respectively. These transitions favour an octahedral symmetry for the Fe(III) complex.

The important bands in the infrared spectra of the ligand and Fe(II) and Fe(III) complexes are discussed. The data indicate that the ligand molecules are attached to the metal ions through nitrogen of azomethine and oxygen of carbonyl group 11 '12. There is no evidence for the presence of lattice or coordinated water in both the complexes as can be seen from the absence of peaks corresponding to (H-0-H) bending of lattice water and rocking and wagging vibrations of coordinated water.

The peaks observed at 1200, I 070, 985, 625 and 455 cm-1 in the spectrum of iron(II) complex correspond to v3• v3, v1. v2 and v4 modes of vibration of unidentate sulphate. Nakamoto and coworkers 13

. who studied the IR spectra of various sulphate complexes are of the view that the appearance of these peaks is due to lowering of symmetry from Td to Cw.

The peaks observed in the spectrum of Fe(III) complex at 2970 and 2890 cm-1 corresponding to the­CH3 asymmetric and symmetric vibrations 14 did not appear in the spectrum of the free ligand indicating coordination of solvent molecules to the metal ion. Aggarwal and Rao 15 who synthesized and characterized different metal complexes with isonicotinic acid hydrazide, also observed that the solvent (ethanol) molecules are coordinated to the metal ion in Fe, Ni and Cu complexes.

The structures proposed for iron(II) and iron(III) complexes of 3-hydroxbenzaldehyde isonicotinic acid hydrazones are shown in Fig. 1.

@H C-N II I H-@ 0 N=C \I

HO Oj50- Fe -oso3 CH

ln\_c=/ \ ~HI H

~-c'@

(a)

J

2-

Fig. 1-(a) Structure of iron(ll) complex of 3-hydroxy­benzaldehyde isonicotinic acid hydrazone (Diammonium disulfate [4-pyridine carboxylic acid [(3-hydroxyphenyl)-methylene hydrazide]- iron(ll)). (b) Structure of iron(lll) complex of 3-hydroxybenzaldehyde isonicotinic acid hydrazone (Dimethanol dichloro [ 4-pyridine carboxyphenyl- methylene]hydrazide]-iron( I+ )chloride).

NOTES 1185

The Fe(II) and Fe(III) complexes of 3-hydroxy­benzaldehyde isonicotinic acid hydrazone are found to be insoluble in any of the deuterated solvents and as such 1H NMR spectral studies in liquid state could not be carried out. These two complexes did not give good spectra even in solid state due to their high paramagnetic character.

The magnetic moments evaluated from magnetic susceptibility data at 298.15 K for [FeL2(S04h](NH4)2 and [FeLCh(MeOH)z]CI respectively are 5.62 11s and 6.01 11s which indicate the presence of 4 unpaired electrons in Fe(II) complex and 5 unpaired electrons in Fe(III) complex and show their paramagnetic character. The observed values of 5.62 11 s for Fe(II) complex and 6.0 I 11 s for Fe(III) complex correspond to the high spin octahedral formulation of the complexes. It may be mentioned here that the high spin octahedral Fe(II) and Fe(III) complexes with the bidentate ligand 2-hydroxy-4-methoxy-5-methyl-chalcone oxime studied by Bhave and Kharat 16 showed almost identical magnetic moments.

The isomer shift and quadrupole splitting observed for [FeL2(S04h](NH4h at 298.15 K respectively are 1.37 mm s- 1 and 1.62 mm s- 1

• These values are within the range observed for octahedral complexes of iron 17

and the metal ion in the complex has the outer electron configuration of 3d6 and is in 50 state. The isomer shift and quadrupole splitting observed for [FeLCI2(MeOH)2]Cl at 298.15 K respectively are 0.69 mm s -I and 0.41 mm s -I. The electric field gradient from the ferric ion in 3d5 electron configuration with 6s state is negligible. However, the small quadrupole splitting observed may be attributed to the field gradient from the neighbouring ions.

The ESR spectrum of iron(III) complex at 298.15 K shows two signals, one relatively strong at g = 2.02 and the other a weak signal at g = 4.21. An ESR spectrum of this type is generally found in the class of compounds where Fe(III) is in an octahedral environment having a rhombic distortion. It may be mentioned here that ESR spectra of similar nature has been observed by Lobana et al. 18 in the iron(III) complexes of bis(tertiary phosphine/arsine oxides) having octahedral geometry. The Fe(ll) complex of 3-hydroxybenzaldehyde isonicotinic acid hydrazone did not show ESR signals at room temperature. This observation indicates that the spin-lattice relaxation time is very short due to spin-orbit coupling within the 5T2g ground state of 3d6 and the zero field splitting

is very large because of small departures from the exact octahedral geometry of the complex .

The X-ray diffractogram of iron(II) complex shows 18 prominent reflections between 15° and 80° with the maximum intensity peak occurring at 28 = 36°25' which corresponds to d = 3.114 A 0 • For iron(III) complex, the diffractogram consists of 13 prominent peaks in the range 30° to 85° with the diffraction peak of maximum intensity occurring at 28 = 41 °54' which corresponds to d = 2.709 A o . All the main peaks in the diffractograms of the two complexes are indexed on evaluating the unit cells by trial and error method 19

·20

. There is a good agreement between the observed and calculated d values and the observed values fit well into the tetragonal crystal system. The lattice constants a, c; the cell volume, V; the number of formula units, Z, in the unit cell; the bulk crystal density, D; and the formula weight, W; for iron(II) and iron(III) complexes found respectively are I 0.371 A0

, 19.463 A0, 2093.394 Ao \ 4, 2389 kg m-\ 753

and 11.069 A0, 7.433 A0

, 910.712 Ao 3 2, 1675 kg m-3

, 459. The formulae weights obtained from X-ray data compare well with the formulae weights determined from elemental analyses data for these complexes.

Acknowledgement The authors are thankful to the authorities of

CDRI, Lucknow, RSIC, Bombay and RSIC, Chennai for providing elemental analyses; X-ray powder diffraction patterns, ESR spectra, 1H NMR spectra and magnetic susceptibility measurements. One of the authors (PMR) is thankful to the UGC, New Delhi , for the award of FIP research fellowship.

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