Ultraviolet and Vibrational Spectral Studies on Biologically Active Complexes of Cobalt – Ii with Benzimidazole Compound

Ultraviolet and Vibrational Spectral Studies on Biologically Active Complexes of Cobalt – Ii with Benzimidazole Compound

1Dr. Ishwar Singh, 2Dr. Pradeep Kumar ,3Dr. Jyotsna Pandit,4Dr. Manish Rao Ambedkar

1,2,3Department of Applied Science,

Mangalmay Institute of Engineering and Technology,Greater Noida

4Department of Chemistry, Greater Noida Group of Institutions Greater Noida

Abstract-We have study the vibrational and ultravoilet spectra in this paper. Widely studies of different carbonic anhydrases

(1) and alkaline phosphatases (2) indicate the presence of a catalytic Co2+ bound to three imidazole residues of enzyme histidines. In the carboxy peptidases (3) and in thermolysin (4), the critical Co 2+ is bound to two imidazoles and a carboxylate group of the enzyme. Inspite of the obvious interest such systems would have few chelating ligands using imidazole rings have been made so far, and none which combine three simple imidazole rings as models for the metal

binding sites of carbonic anhydrase.

Keywords: Ultravoilet, Vibrational Spectra, Biological study

INTRODUCTION

Extensive studies of various carbonic anhydrases(1) and alkaline phosphatases(2) indicate the presence of a catalytic Co2+ bound to three imidazole residues of enzyme histidines. In the carboxy peptidases(3) and in thermolysin(4), the critical Co2+ is bound to two imidazoles and a carboxylate group of the enzyme. Inspite of the obvious interest such systems would have few chelating ligands using imidazole rings have been made so far, and none which combine three simple imidazole rings as models for the metal binding sites of carbonic anhydrase.

Frutons(4) synthesis from histidine is not adaptable for the preparation of related tris (imidazoles). Thompson et.al(5) have described some metal binding properties of a tris (benzimidazole) ligand system(4). Finally the tris (pyrazolyl) borohydride ligand(5) first reported by Trofimenko(6) but studied by Marks and Ibers. The Xray studies(5) on carbonic anhydrase show that the three imidazole ligands have distorted tetrahedral coordination to the Co2+. Molecular models suggested that a similar geometry could be attained with a tris (imidazolyl) methane derivate(7,8).

Benzimidazole complexes of transition metals exhibit interesting spectral and magnetic properties(9.10). Oxime function located adjacent to another donor atom in an organic molecule, can act as a versatile chelating group and may make the molecule useful in the separation and estimation of metal ions(11). These considerations prompted us to synthesise new polydentate ligands containing both oxime and imidazole functions together. Here we discuss the synthesis and characterization of the complexes of 2Acetyl4|methyl benzimidazole oxime (ACMBZOXH2) or 2benzoyl4|methylbenzimidazole oxime (BzMBzOXH2) with Co(II).

EXPERIMENTAL

Material and Methods: The chemicals used were of AR or equivalent purity, 4Methyl2Acetyl benzimidazole and 4methyl2benzoyl benzimidazole were prepared by the reported methods.(12) Their oximes were prepared by refluxing the ketone and hydroxylamine hydrochloride in ethanol in presence of pyridine. The excess of ethanol was removed by distillation or evaporation oximes were purified by recrystallisation from methanolbenzene mixture.

Synthesis of Complexes: To an ethanolic solution of 2Acetyl benzimidazole oxime (0.005 mol), metal (II) chloride/nitrate/sulphate (0.005 mol) in the same solvent or metal(II) acetate in water was added. The resulting mixture was refluxed on a water bath for 2hour cooled and filtered, washed with ethanol and dried over phosphorous pentoxide.

In the synthesis of 4methyl2benzoyl benzimidazole oxime complexes, the ligand (0.005 mol) was dissolved in the minimum quantity of ethanol and metal(II) chloride/acetate (0.005 mol) in water was added. The resulting precipitate was refluxed on a water bath for 2hour cooled, filtered and washed with aqueous ethanol and dried, over phosphorous pentoxide.

H H

N

N

(1)

N N

H N

N (4)

HN N

HN

CH2 N

3

(2)

N NH

NH

N

(5)

HN N

4 – BIM (3)

N BH

3

N NH

Results and Discussion: The elemental analysis of the complexes along with their magnetic moment data are given in table-1. The complexes are insoluble in common organic solvents except in DMF, DMSO and pyridine. The molar conductances of 103M DMFsolutions of the complexes were found to be in the range 730 mho cm2 mol1. The slightly higher values than those of expected for non electrolytes indicate the solvation of the complexes resulting in the displacement of anion from coordination sphere by

strong donor DMF molecules. The complexes may be regarded as non electrolytes.

Magnetic Properties: The cobalt(II) complexes [Co(C10H10N3O)]Cl and [Co(C10H10N3O)2]2H2O show

moment values of 3.95 and 4.02 B.M. respectively. These are much lower than the values expected for tetrahedral (4.2

4.7 B.M.) or octahedral (4.7 5.2 B.M.) cobalt(II) complexes. This lowering of magnetic moment may be explained by assuming the coexistence of high spin as well

nitrogen and tertiary imidazole nitrogen. The NOH group is deprotonated as shown by the disappearance of the ligand band at 32503280 cm1. A band at 33603450 cm1 is assigned to (OH) of coordinated water. The coordination through oxime nitrogen and tertiary nitrogen is suggested from the lowering of (C=N) as in type (a) complexes.

In type (c) [Co(C10H10N3O)]Cl complex the ligand behaves as a monobasic tridentate ligand coordinating through the oxime nitrogen, pyrrole nitrogen and tertiary nitrogen of imidazole moiety thus forming a polymeric

as low spin states of Co(II) (t

5e 2 t

6 e 1) the

complex(19). (OH) of oxime function is observed at 3240

2g g

2g g

cm1 due to hydrogen bonding with chloride. (NH)

presence of antiferromagnetism or the polymeric nature of the complexes.(20,21)

The effective value of [Co(C15H12N3O)2].2H2O (4.90 B.M.) agrees very well with the expected value for octahedral cobalt(II).

Ultervoilet Spectra: The electronic spectra of [Co(C10H10N3O)]Cl showed a multicomponent band at 14815 cm1 which is typical of a tetrahedral cobalt(II) complex. This is assigned to 3band resulting from 4T1(P) 4A2 transition. The band observed at 6896 cm1 may be taken as 2 band 4T1(F) 4A2. The spectrum of [Co(C10H10N3O)2]2H2O was quite different from that of [Co(C10H10N3O)]Cl and showed two bands at 20490 and 7145 cm1. These are assigned to the transitions 4T1g(P) 4T1g(F) and 4T2g 4T1g(F) respectively of octahedral Co(II) complex. The 2 band, since it involves a two electron transition was not observed. Its position was calculated using konig equation.(13-16) The various ligand field parameters (Dq, B, , 2/1 and LFSE) have been calculated. The 2/1 ratio for [Co(C10H10N3O)2].2H2O is found to be in the range (2.1 2.2) which is reported for octahedral cobalt(II) complexes.(17-19) Satisfactory electronic spectrum could not be obtained for [Co(C15H12N3O)2].2H2O.

Vibrational Spectra: A comparison of the infrared spectra of the ligands and their complexes indicated that the benzimidazole oximes were coordinated to the metal in the present complexes in four different ways

(a d)

In type (b) [Co(C10H10N3O)2].2H2O and [Co(C15H12N3O)2].2H2O complexes, the ligands behave in a mono basic bidentate manner coordinating through the oxime

disappears confirming deprotonation and coordination through the itrogen. The coordination through oxime nitrogen and tertiary nitrogen is suggested by the lowering of (C=N), (NO) in the ligands assigned of 935950 cm1 shifts to higher frequency as a result of coordination through oxime nitrogen.

CONCLUSION

In conclusion, we have widened a practical and novel procedure for the selective synthesis of cobalt(II) complexes [Co(C10H10N3O)]Cl and [Co(C10H10N3O)2]2H2O by using

infrared and electronic spectra. The present procedure has a several advantage, mild reaction, non harzadous methed, experimental easy and simple workup process, less reaction time to conventional method

REFERENCES

1. H.N. Fernley, Enzymes 3rd Edn. 4 (1971) 417.

2. R. Breslow and D.L. Wernick, Proc. Natl. Acad. Sci. U.S.A. 74 (1977) 1303.

3. W.R. Kester and and B.W. Mathews, J. Mol. Chem. 252 (1977) 7704.

4. C.N.C. Drey and J.S. Fruton, Biochemistry 4 (1965) 1; 4 (1965) 1258.

5. C.K.Thompson, B.S.Ramaswamy & E.A.Seymour, Can. J.Chem. 55(1977) 877.

6. S. Trofimenko, Chem. Rev. 72 (1972) 497 Acc. Chem. Res. 4 (1971) 17.

7. M. Goodgame, & F.A. Cotton, J. Am. Chem. Soc; 84 (1964) 1543.

8. N. Shashikala, E.G. Leelamani and G.K.N. Reddy, Ind. J. Chem. 21A (1982) 743; J. Ind. Chem. Soc. 62 (1985) 928.

9. P.K. Nath, N.C. Mishra, V.Chakravorty & K.C. Dash, Polyhedron 6 (1987) 455.

10. C. Keshavolu, R.S. Naidu & R.R. Naidu, Polyhedron 4 (1985) 761.

11. Madan Mohan & Munesh Kumar, Polyhedron 4 (1985) 1929.

12. B. Egneus, Talanta 19 (1972) 387.

13. G.W.H. Cheeseman, J. Chem. Soc. (1964) 1387.

14. A. Bistrzycki & G. Przeworski, Berft. Chem. Ges. 45 (1912) 3492.

15. D.L. Williams, D.W. Smith, & R.C. Stanfer, Inorg. Chem. 6 (1937) 590.

16. N. Mondal, M.K. Shah, S.Mitra & V. Gramlich, J. Chem. Soc. Dalton Trans. (2000) 3218.

17. J.M. Clemente, Juan, B. Chansou, B.Donnadieu and J.P. Tuchagues, Inorg. Chem. 39 (2000) 5515.

18. S.H. Rahaman, R. Ghosh, D. Bose, H.K. Fun & B.K. Ghosh, Ind. J. Chem. 43A (2004) 1901.

19. L.K. Thompson and S.S. Tandon, Inorg. Chem. 18 (1996) 125.