Steric effects in controlling co-ordination environment in zinc 2-nitrobenzoate complexes

A dinuclear zinc complex having exclusive bis(unidentate) carboxylato co-ordination mode is synthesized through two-step reactions, involving solid phase reaction followed by solution reaction. The formation of such dinuclear species is governed by the ligand under consideration. For example, 2-nitrobenzoate zinc complex having 1,10-phenanthroline is mononuclear whereas a similar complex with 8-aminoquinoline is dinuclear having bis(unidentate) carboxylato co-ordination mode. The reasons for the formation such complex is explained on the basis of the distance of separation of uncoordinated oxygen atoms of the carboxylate oxygen of mononuclear and dinuclear complexes. Zinc 2-nitrobenzoate complexes having 2,2′-bipyridine is mononuclear but with 2-aminopyrimidine has a dinuclear paddle wheel structure. Solution phase reaction of 2-nitrobenzoic acid with zinc(II)acetate in the presence of 8-aminoquinoline gives bis-(8-aminoquinoline)zinc(II) 2-nitrobenzoate.