BIRENDRA KUMAR¹*, KIRAN KUMARI PRASAD and SANJAY KUMAR SRIVASTAWA²

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1 Oriental Journal of Chemistry Vol. 26(4), (2010) Synthesis of oxygen bridged complexes of Cu(II) or Ni(II)- salicylaldoxime with alkali metal salts of some organic acids studies on their antimicrobial activities BIRENDRA KUMAR¹*, KIRAN KUMARI PRASAD SANJAY KUMAR SRIVASTAWA² ¹P.G. Department of Chemistry, Maharaja College (V. K. S. U.), Ara (India). ²Department of Chemistry, S.G.G.S. College (M.U.,Bodh Gaya), Patna (India). *B/8, Bari Patan Devi Colony, Gulzarbagh, Patna (India). (Received: July 10, 2010; Accepted: August 11, 2010) ABSTRACT The copper(ii) nickel(ii)-salicylaldoxime, M a have been used as a complex lig in the synthesis of a number of oxygen bridge complexes of the general formula M a.(m b L) 2, M a acting as a bidentate complexing agent, coordinating through two oximino oxygens to alkali metal salt (M b L) (where M b = Li, Na or K; L = deprotonated 8-hydroxyquinoline or 1-nitroso-2-naphthol). The structure has been substantiated by infrared, electronic absorption spectra magnetic moment measure-ments. Most of the compounds have shown significant activity against test bacteria, e.g. E. coli, S. aureus fungi, e.g. C. albicans. Key words : Alkali metal, salicylaldoxime, infrared spectra, biological activity. INTRODUCTION Salicylaldoxime is an important lig containing both a O-H(phenolic) an oxime group at the ortho position. The formation of oxygen bridge complexes from salicylaldoxime is well established 1-7. Salicylaldoxime was used first as a lig for complexation of metal ions by F. Ephraim as early as X-ray structural reports on the square planar complexes of the divalent metals Ni(II), Pd(II) & Pt(II) were published shortly after that in Phenolic oximes find extensive use in industry, mainly as extractants for copper 8 but also as anticorrosives in protective coatings 9. Keeping this view in mind, we thought that it would be of interest to study the reactions of copper(ii) nickel(ii) metal chelates with alkali metal salts of some organic acids. We have selected Cu(II) or Ni(II)-salicylaldoxime, i.e. as metal complex ligs. EXPERIMENTAL Materials Copper(II) acetate nickel(ii) acetate were used of E. Merck quality. The organic acids were used; 8-hydroxyquinoline 1-nitroso-2- naphthol of BDH A.R. quality. Salicylaldoxime was used also of BDH A.R. quality. Preparation of transition metal chelates, M a Ethanolic solution of 0.1mole of copper(ii) acetate or nickel(ii) acetate was taken in a conical flask then 0.2 mole of salicylaldoxime was added. The whole content was was refluxed with continuous stirring on magnetic hot plate for 30 minutes at 80 0 C. Green or steel grey precipitate of transition metal chelate was separated out. It was filtered, washed with absolute ethanol dried in an electric oven at 80 0 C.

2 1414 Kumar et al., Orient. J. Chem., Vol. 26(4), (2010) Preparation of alkali metal salts of organic acids, M b L 95% ethanolic solution of 0.01 mole of organic acid 0.01 mole of alkali metal hydroxide were mixed. The mixture was refluxed on magnetic hot plate for 1-1½ hours with continuous stirring at 80 0 C. On cooling the resulting solution, a characteristic colour precipitate was obtained. It was filtered, washed with pure solvent dried in an electric oven at C. Preparation of oxygen bridged complexes(adducts), [M a.(m b L) 2 ] mole of copper(ii) or nickel(ii)- salicylaldoxime, or was taken in absolute alcohol mole of alkali metal salt of organic acid (8-hydroxy-quinoline or 1- nitroso-2-naphthol) was added with constant stirring. The whole contents were refluxed on a hot plate at 80 0 C with constant stirring for 1-2 hours. A characteristic colour adduct was precipitated in room temperature. But some adducts are precipitated in hot condition or reactions start quickly. The precipitate was filtered, washed thoroughly with absolute ethanol, dried in an electric oven at 80 0 C. RESULTS AND DISCUSSION Some physical properties analytical data of the metal chelates their adducts are listed in Table-1. From the results, it is evident that the adducts have characteristic colour are different from the metal chelates. All the adducts show high melting/decomposition temperatures which indicate their greater stability. Molar conductivities Molar conductivities(in ohm -1 cm 2 mol -1 ) of compounds were measured in DMSO at 30 0 C at a concentration of 10-3 M (Table-1). The compounds show low values ( ohm -1 cm 2 mol -1 ) of molar conductivities, indicating that they are covalent in nature. The strong absorption bs at 3450 & 3435 cm -1 in the infrared spectra of metal chelates, & respectively have been assigned to OH stretching. The presence of these bs two other bs, i.e. at 2401cm cm -1 in the metal chelates point out to presence of strong intramolecular hydrogen bonding. In theoxygen bridged complexes, the intensity of the b at 3450 cm -1 & 3435 cm -1 have reduced to cm -1 & cm -1 respectively, other bs in the region of cm -1 suggest the strong intramolecular hydrogen bonding in the oxygen bridged complexes. The metal complexes, as ligs exhibit the υ C-O (phenolic) at 1538 cm -1, which shifted upto 36 cm -1 on oxygen bridged complex formation, indicating the coordination through the phenolic oxygen. This shift is expected due to maintenance of a ring current arising from electron delocalization in the chelating ring. The major shift of υ C-O (phenolic) to lower energy by ~ 36 cm -1 in complexes certainly indicates the presence of phenoxo bridge. The characteristic absorption bs of υ C=N/ υ C=C(aromatic) stretching vibration observed at 1648/ 1598 cm cm -1 in respectively. So, appreciable shifts after the formation of oxygen bridged complexes of with alkali metal salts of some organic acids. x Infrared spectra Infrared spectra of metal chelates their adducts were recorded in KBr phase between cm -1 with the help of FTIR spectrophotometer, Shimadzu model-8201pc. Selected IR absorption bs of the compounds are given in Table-2. x Fig. 1:

3 Kumar et al., Orient. J. Chem., Vol. 26(4), (2010) 1415 Table 1: Colour, decomp. temp., molar conductance, magnetic moments & elemental analysis of the complexes Compound Colour Decomp. Molar cond. Magnetic % Analysis Found/ (Calc.) temp.( 0 C) (ohm -1 cm 2 mol -1 ) moment (in BM) C H N M a M b Blackish 245d green (60.91) (3.81) (8.76) (10.07) (2.22) Light 238m green (57.35) (3.58) (8.36) (9.48) (6.87).(K8HQ) 2 Yellowish 250m green (54.74) (3.42) (7.98) (9.05) (11.12).(Li1N2N) 2 Light 270d brown (58.83) (3.46) (8.07) (9.16) (2.02) Orange 238md brown (54.73) (3.22) (7.51) (8.52) (6.17) Deep 285d brown (53.86) (3.17) (7.39) (8.38) (10.30) LIght 260md green (60.69) (3.79) (8.85) (9.28) (2.12) Parrot 285d green (57.77) (3.61) (8.42) (8.83) (6.92).(K8HQ) 2 Deep 290d green (55.12) (3.44) (8.04) (8.42) (11.19).(Li1N2N) 2 Reddish > brown (59.24) (3.48) (8.13) (8.52) (2.03) Deep > brown (56.61) (3.33) (7.70) (8.14) (6.38) Deep 290d brown (54.20) (3.19) (7.44) (7.80) (10.36)

4 1416 Kumar et al., Orient. J. Chem., Vol. 26(4), (2010) The υ N-O b of at 1148 cm -1 show a appreciable change in oxygen bridged complexes which are observed between cm -1 another b at 1216 cm -1 remain unaffected in most of the oxygen bridged complexes. The υ N-O b of at 1219 cm -1 splits into two absorption bs which are observed between cm -1 in the oxygen bridged complexes. This is probably due to the presence of symmetric asymmetric stretching b of N-O of oxime group. In all the present complexes, the bs with medium to strong absorption in the far infrared region cm cm -1 tentatively assigned to υ M-O υ M-N modes 10 respectively. These bs are not present in salicylaldoxime. While in neutral transition metal chelates, at region cm cm -1. These assignments are based on the assumption 11 that since oxygen atom is more electronegative than nitrogen, the M-O bond tends to be more ionic than the M-N bond. Consequently M-O vibrations are expected to appear at higher wave number. The above data confirm the coordination of oxygen atoms of phenolic group oximino group to alkali metal in all the oxygen bridged complexes. Electronic absorption spectra Electronic absorption spectra of metal chelates their adducts were recorded on Systronic Double Beam UV-VIS spectrophotometer in methanol. The bs observed in electronic spectra of the compounds are listed in Table - 2. Electronic absorption bs are observed between Table 2: IR & electronic absorption bs of CuEA, NiEA their complexes Compound IR absorption bs (in cm -1 ) Diffuse reflectance υ O-H/O H O υ C-O υ C=N υ N-O υ M-O/M-N (in nm) 3150, , 1216, 613,585, 326,348,382, ,3195, 1541, 1605, 1217, 545,510, 319,355,391, , , 1216, 565, ,362,391,412, ,2377, , ,391,405,416, ,3022, , 1216, 548,505, 348, , , 1214, 588, , , Table 3: Antibacterial antifungal activity of the adducts Compound Minimum Inhibitary conc. (in µgml -1 ) E. coli S. aureus C. albicans

5 Kumar et al., Orient. J. Chem., Vol. 26(4), (2010) nm in the metal chelates, show that there is charge transfer as well as d-d transition. The spectra of all the oxygen bridged complexes also gave similar type of bs in the region of nm nm. This suggests square planar geometry in all the complexes so there is no change in stereochemistry of after complex formation. This is supported by the magnetic moment value of the complexes. The electronic absorption bs located in the region nm may be attributed to arise due to charge transfer. However, the possibility of peak in the region nm. The absorption bs of medium intensity in in the region nm in electronic spectra, suggests the square planar structure of Ni 2+ with the coordination number 4. The absorption bs of oxygen bridged complexes derived from is found in the region of nm, suggesting the same square planar geometry of with coordination number 4 in all the complexes. Magnetic moment Magnetic moment of metal chelates their adducts have been measured by Can Faraday magnetic susceptibility balance at 30 0 C. The magnetic moment values are shown in Table -1. As a rule the magnetic moments fall in the range BM, the magnetic moment of has been found to be 1.78 BM, suggesting their square planar geometry with coordination number 4, while the magnetic moments of oxygen bridged complexes are in between 1.78 to 2.15 BM corresponds to the presence of one unpaired electron. Therefore, the stereo-chemistry of unit in the complexes remain almost same. Very low values (approaching to zero) of magnetic moment (µ eff. ) of its oxygen bridged complexes, suggesting their diamagnetic nature. This observation also suggests their square planar geometry with coordination number 4 for Ni 2+ ion. Microbiological studies Minimum inhibitory concentration(mic) values (in µgml -1 ) of some of the prepared oxygen bridged complexes of have been examined by serial dilution method 12 for activity against some bacteria, viz. E. coli, S. aureus fungi, viz. C. albicans. The results are summarized in Table - 3. The results of antibacterial antifungal activity evaluation revealed that four of the bimetallic complexes,,. (K1N2N) 2,. (Na1N2N) 2. were relatively potential inhibitor of the growth of both the test bacteria one fungi. The MIC values of at a concen-tration of 35 µgml -1 while at a concentration of 25 µgml - 1 for E. coli. The MIC values of,, at the concentration 40 µg ml mgml -1 respectively for S. aureus. The MIC values of all the four bimetallic complexes at the same concentration 30 µgml -1 for fungi C. albicans. Structure & Bonding The bonding between the transition metal chelates, M a the alkali metal is most likely to occur by dative bonding via the phenolic oximino oxygen atoms, which has been supported by the infrared, electronic absorption spectral studies magnetic moment measurements. The probable structures of the newly prepared oxygen bridged complexes, M a.(m b L) 2 may be produced schematically as such (Fig. 1). REFERENCES 1. Pfiffer P., Breith E., Lubbe E. Tsumaki T., Ann. 84: 503 (1933). 2. Lee K. Lee W. S., J. Kor. Chem. Soc., 39(8) (1995)

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