Abstract

N. P. Singh¹, M. N. Srivastava¹ and G. Kumar²

Mixed ligand complexes of some transition metals, Cu (II), Ni (II) and Co (II) formed with histidine and adenine or guanine have been synthesised and characterised by their elemental analysis, magnetochemical measurements and spectral studies (IR and electronic spectra). Histidine in general shows tridentate behaviour, whereas adenine and guanine are bidentate. With adenine, co-ordination occurs at N3 - N9 (-NH) positions whereas, with guanine co-ordination occurs through the carbonyl oxygen and N7 (C6O-N7). The remaining co-ordination positions are satisfied by the bridging OH groups and water molecules. Thus all these except the Co (II)-histidine-adenine complex, are binuclear complexes. Cu(ll)-hisstidine-adenine/guanine complexes have pentaco-ordinated (possibly square pyramidal) structure, whereas Ni(ll)-histidine-adenine/guanine complexes show mixed stereochemistry (octahedral + square planar). The Co (ll)-histidine-adenine/guanine complexes are square planar.

magnetochemical; synthesised; stereochemistry

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