INVESTIGATIONS ON THE SPIN-CROSSOVER COMPLEX [FE(BZIMPY)2](CLO4)2 AND ITS MN-2+, CO-2+, NI-2+ AND ZN-2+ ANALOGS

A series of transition metal complexes [M(bzimpy)2](ClO4)2 (M = Mn2+, Fe2+, Co2+, Ni2+, Zn2+; bzimpy = 2,6-bis(benzimidazol-2'-yl)pyridine) was synthesized and characterized by elemental analysis, UV-Vis and far-IR spectroscopy. The electronic spectra of [Ni(bzimpy)2](ClO4)2 in solution and solid state reveal a ligand field splitting parameter DELTA(o). in the range of 11470 cm-1 to 11840 cm-1. The simultaneous existence of two species with distinct spin state is found for [Fe(bzimpy)2](ClO4)2 by means of variable temperature far-IR measurements. Assignments of the observed far-IR bands are given on the basis of the investigations of the variation of the metal ion in [M(bzimpy)2](ClO4)2.