Molecular and electronic structures of the members of the electron transfer series [Mn(bpy)3]n (n = 2+, 1+, 0, 1-) and [Mn(tpy)2]m (m = 4+, 3+, 2+, 1+, 0). An experimental and density functional theory study.

ABSTRACT

The members of the electron transfer series [Mn(bpy)3](n) (n = 2+, 1+, 0, 1-) and [Mn(tpy)2](m) (m = 2+, 1+, 0) have been investigated using a combination of magnetochemistry, electrochemistry, and UV-vis-NIR spectroscopy; and X-ray crystal structures of [Mn(II)((Me)bpy(•))2((Me)bpy(0))](0), [Li(THF)4][Mn(II)(bpy(•))3], and [Mn(II)(tpy(•))2](0) have been obtained (bpy = 2,2'-bipyridine; (Me)bpy = 4,4'-dimethyl-2,2'-bipyridine; tpy = 2,2'6,2″-terpyridine; THF = tetrahydrofuran). It is the first time that the latter complex has been isolated and characterized. Through these studies, the electronic structures of each member of both series of complexes have been elucidated, and their molecular and electronic structures further corroborated by broken symmetry (BS) density functional theoretical (DFT) calculations. It is shown that all one-electron reductions that comprise the aforementioned redox series are ligand-based. Hence, all species contain a central high-spin Mn(II) ion (SMn = 5/2). In contrast, the analogous series of Tc(II) and Re(II) complexes possess low-spin electron configurations.