Electronic Absorption Spectra of Tris(2,2′-bipyridine)- and Tris(1,10-phenanthroline) Complexes of Vanadium(II) and Chromium(II)

Abstract Electronic absorption spectra of tris(2,2′-bipyridine) complexes of vanadium(II) and chromium(II) were measured. When methyl groups are introduced into the coordinating bipyridine, (d, d*) transitions in the central metal, (π, π*) transitions in the coordinating ligand, and “metal to ligand” charge-transfer transitions show their respective characteristic shifts. Thus the visible and near-infrared bands of tris(2,2′-bipyridine) complexes of vanadium(II) and chromium(II) are assigned to “metal to ligand” charge-transfer transitions as well as the visible bands of tris(2,2′-bipyridine)iron(II). A comparison between the corresponding bands of tris(2,2′-bipyridine) complexes and tris (1,10-phenathroline) complexes also verifies the assignment.