配基bpy和[Fe(bpy)3]2+ 電子密度分布之研究

Abstract

[FeII(bpy)3][FeII2(ox)3] contains two different spin states of Fe atom in the same crystal according to Mossbauer spectra and magnetic measurement. It’s a good candidate of charge density study to see the difference in electronic distribution around Fe at high spin or low spin state. The experimental result has verified that [FeII(bpy)3]2+ is in LS state and [FeII2(ox)3]2- is in HS state. This work is mainly the corresponding study using DFT theoretical calculations. The first part is focused on the study of the free ligand trans-bpy. The purpose is to understand the effects of various parameters on the charge density and the geometry. It turns out the percentage of hybrid exact HF exchange is more important than the correlation part. Finally, B3P86 XC functional(hybrid HF=20%) with 6-31G(d,p) basis set is used to conduct a single point calculation. The second part is on the charge density of [FeII(bpy)3]2+ cation. The calculation method is the same as that in free ligand, with the additional basis set of 6-311G(d,p) for Fe atom. The topological properties are compared with the experimental data in terms of deformation density and Laplacian map. It’s clear that around Fe, local chagre depletions are at the σ directions and local charge accumulations are at the corner of a cube around Fe, i.e. at the π directions. The exact electronic density distribution around Fe is illustrated by its atomic graph. According to ρ and ▽2ρ and total energy density Hb at bond critical point, Fe－N bond is a polarized colvalent bond which is stronger than that of Fe－O bond. Fortunately, the consistence between the theory and the experiment is good. The Fe in cation [FeII(bpy)3]2+ is definitely at LS state. d-orbital populations derived from experiment and theory are also in great agreement.