The Complex compounds of Pyridine-3 Carboxylic Acid Hydroxyl-methyl amide with Ni (II), Cu (II) and Cr (III)

 

Sharat Chandra

Ex-Research Scholar, Jai Prakash University Chapra (Bihar)

*Corresponding Author E-mail: tiwary_cb@rediffmail.com

 

 

INTRODUCTION:

The present ligand which has significant activity against several diseases with ligation character possess three potential binding sites for the metal ions being ring nitrogen, carbonyl and alcoholic oxygen atoms. But a perusal of literature showed that its complexes with the metal ions not have been isolated as yet. So, it was thought worthwhile to introduce it as a new ligand, isolate its metal complexes and to infer on the basis of evidences, the mode by which these potential sites (which also being the subject of steric hindrance due to unsuitability in presence of CO and alcoholic OH with respect to ring nitrogen, while coordinating to the same metal ions) are bound. Thus the present study deals with the study of complexes of Nickel (II), Cu (II), Fe (II) and Cr (III).

 

METHODS AND MATERIALS:

In the present work, NiSO_4.6H₂O, CuCl₂.2H₂O, CrCl₂.6H₂O, FeSO₄.7H₂O and Pyridine-3-Carboxylic acid Hydromethyl amide of Enthor grade were used as materials.

 

The elemental analyses were performed by the standard methods. Magnetic measurements were done on Guoy’s balance IR. Spectra of the ligand and complexes in KBr phase in the range of 4000-200 cm^-1were made by using Perkin Elmer 621 spectrophotometer. The electronic spectra of the complexes were recorded using Hilger Unispek Spectronic 20.

 

There aqueous solution of 0.02M of the metal ions and ethanolic solution (0.02M) of the ligand were used in the complex formation as standard solution in required experimentation. The Ni (II)-, Cr (III)- and Fe (II)- complexes were prepared by mixing hot solutions of the metal ions and ligand (cold solutions of ferrous ions and ligand) in 1:2 molar ratio and raising the pH values to 6-8 with normal NH₄OH solution. The Cu (II)- complex was prepared by mixing Cu⁺² ions and ligand in 1:1 molar ratio and raising the pH to 8. All complexes were filtered separately through a weighed sintered glass crucible no. 3, washed with hot distilled water and dried in air except the Fe (II) complex, which was washed with cold water and dried in a vacuum desiccator.

 

RESULTS AND OBSERVATIONS:

The complexes are sparingly soluble in methanol, acetone and carbon tetrachloride. The dilute mineral acids liberate free ligand from them. The Ni (II), Cu (II) and Cr (III) complexes are stable in air, but Fe (II) complex seem unstable as its dark green colour gradually changes to dirty brown or chocolate colour in air or in presence of supernatant water (Table 1).

 

Table 1. Complexes colour, analytical data and electronic absorption spectra.

Complexes pH colours	Analytical Data			µeff		λmax  cm-1
	% M present (Calcd)	% C present (Calcd)	% N  present (Calcd)	% N present (Calcd)	BM
Ni(LH)2SO4 6.0 Green   CuLC1 8.0 Green   Fe(LH)2SO4 6.0 Deep green   Cr(L)2Cl 8.0 Green	16.26 16.28 17.27 17.31 17.34 17.34 16.38 16.40	46.57 46.57 45.96 45.99 26.00 26.06 26.47 26.49	3.87  3.89  3.83  3.86  3.08  3.10  2.82  2.85	15.50 ……. 15.30 15.31 88.65 8.69 88.82 8.84	2.9   1.9   5.3   3.9	8750, 14800, 25400 15600, 18250, 35800 10100, 12200 16500, 23800, 36900

 

Magnetic Moment:

The magnetic moments 1.9, 2.9, 3.9 and 5.3 BM of Cu (II), Ni (II), Cr (II) and Fe (II) complexes respectively against the presence of 1, 2, 3 and 4 unpaired electrons in them and so they are paramagnetic. The latter three complexes are obviously octahedral, while the former one may be expected to be square planar as the moments of several square planar complexes of Cu (II) have been reported to lie in the range 1.9-2.1 BM. The orbital contribution is almost quenched in the Ni (II)-complexes although it is appreciable in Cu (II)-complex.

 

ELECTRONIC SPECTRA:

The absorption bands at 8750, 14800 and 25400 cm^-1, assignable to the transitions from 3A (F) state to 3T (F), 3T (F) and 3T (F) states respectively suggest the octahedral structure. Dq=875 cm^-1, B=893 cm^-1, B=0.85 and v₂/v₁=1.68 also favours the OH-symmetry and they may be assigned to 2B→2A and 2B→2E transitions respectively, while the bands at 25000 is assigned to C-T. The band at 10100 cm^-1, separated by another peak at 12200 cm-1 in Fe (II)-complex shows its OH symmetry (1). The 101-00 band is due to 5T→5E transition. From Tanabe Sugano diagram, Dq/B=2, Racah parameter of Fe/1060 cm^-1, B= 505 cm^-1 and B=0.47 also support the octahedral structure. The bands at 16500, 23800 and 36900 in the Cr (III)-complex, suggest the OH symmetry. They may be assigned to their transitions from 4A (F) state to 4T (F), 4T (F) and 4T (P) states respectively. Also the other electronic parameters i.e., Dq=1650 cm^-1, B=693 cm^-1, C/B=0.64 and v₂/v₁=1.44 favors the OH symmetry.

 

INFRA-RED SPECTRA:

The system-CO-NH-CH₂-OH is itself bidentate. Due to steric hindrance ring nitrogen, meta CO and the OH group at first glance seem unable to bind the same metal ion, but that is not the fact. Gupta et al (1976) have reported the Fe (II)-complex of amine in which alcoholic oxygen of CHOH moiety linked in 4-position of the ring along with ring nitrogen donated the lone pair to the same Fe (II).

 

Table 2. Relevant bands on spectroscopy of ligand and complexes.

Ligand cm-1	Ni (II) cm-1	Cu (II) cm-1	Fe (II) cm-1	Cr (III) cm-1	Assignments
3180 m 2910bs 1620m 1630s 1590m 1360m …… …… ……	3180m 3010s 1620m 1630m 1600m 1390m 878s 510m 505m	…… 3015s 1630m …… 1605m 1395m 875s 525m 520m	3180m 3018s 1625m 1630m 1603m 1390m 880s 470m 465m	…… 3005s 1615m …… 1595m 1385m 870s 465m 460m	v(M) v(O-H) of CH2OH v(C=N) v(C=O) Ring C=N v(C-N) CH2 rocking v(M-O) v(M-N)

 

In the free ligand, ring of C=N, C=O and OH stretching frequencies are observed at 1590, 1630 and 2910 cm^-1 respectively. The OH frequency is lower due to strong intramolecular H-bonding in free ligand. The extent of lowering usually depends on the strength of H-bonding and the mass effect of carbonyl oxygen with which alcoholic H is weakly bound. Blinc et al (1960) noted O…H-O at 3250 cm^-1. No bond is found for enolic OH in free ligand. But a distinct medium sharp band at 3180 cm-1 in it may be attributed to v (NH). On complexation, ring C=N frequency shows a positive shift to Oxygen. Saha et al (1977) reported the positive shift of C=N frequency by 30 cm^-1. Greenwood (1960) and Ferrado (1969) also reported the positive shift of C=N frequency. Srivastava et al (1976) also reported identical shift of v (C=N) in tertiary pyridal complexes with SH. The C=O frequency is lowered to 1580 cm^-1 only in Ni (II) and Fe (II)-complexes. This indicates that carbonyl oxygen of imide structure in the ligand coordinated to these metal ions. Further, v (NH) is not lost but the intensity is weakened in complexes. Thus, no proton is lost in their formation. The bands around 1120 and 1625 cm^-1, which might have assigned to v (C=O) and v (C=N) respectively are not observed in them. But, C=O and NH frequencies are completely lost in Cu (II) and Cr (III) complexes. Further, two new bands at 1120 and             1625cm^-1, assignable to v (C=O) and (H+) from imidolic form, existed at high pH when H-bonding is corrupted by the ligand field. It is also evident from steric hindrance of ring on carbonyl group, adjacent to-NH-CH₂-as an active moiety. It is supported by Ghosh et al (1976). The alcoholic OH modifies frequency without altering its intensity from 2910 cm^-1 to 3018.05 cm-1 in complexes indicating that coordination takes place through alcoholic OH. Gupta et al (1976) has also reported modification of O-H…N frequency on coordination. The formation of M-N and M-O bonds held for which the bands appeared at 520-450 and 525-460 cm-1. The sharp bands at 249 cm^-1 in Cu (II) complex is probably due to v (Cu-Cl). Thus, on the basis of above evidences the following tentative structure of complexes may be proposed:

 

REFERENCES:

1.     Figgis BN (1976): Introduction to ligand field, Wiley Eastern Ltd, Nerw Delhi.

2.     Gupta SS, Siddiqui S and R Kausal (1976): J. Ind Che Soc, 53: 242.

3.     Blinc R and S Hadzi (1960): Spectrochim Acta:16, 353.

4.     Saha N and Bhattacharya (1977): J Ind Che Soc:53, 143.

5.     Greenwood NH and K Wade (1960): J Che Soc, 1130.

6.     Ferrado JR (1969): Appl Spectra, 23, 160.

7.     Srivastava TN and PC Srivastava (1976): J Ind Che Soc, 53, 365.

8.     Ghosh NN and PC Chaudhary (1976): J Ind Che Soc, 53, 552.

9.     Gupta RR and R Kaushal (1976): J Ind Che Soc, 53, 532.

10.   Malik WU, Benbi R and JK Dwivedi (1976): J Ind Che Soc, 53, 362.

 

 

 

 

Received on 28.06.2019                    Modified on 24.07.2019

Accepted on 30.07.2019                   ©AJRC All right reserved