Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, c/Marcel⋅lí Domingo s/n, Campus Sescelades, 43007 Tarragona (Spain), Fax: (+34) 977-55-9563; Institució Catalana de Recerca i Estudis Avançcats (ICREA), Passeig Lluís Companys 23, 08010 Barcelona (Spain).
Chemistry. 2010 Apr 19;16(15):4550-6. doi: 10.1002/chem.200903423. Epub 2010 Mar 12.
Ab initio calculations have been performed on Fe(II)(bpy)3 (bpy = bipyridine) to establish the variation of the energy of the electronic states relevant to light-induced excited-state spin trapping as a function of the Fe-ligand distance. Light-induced spin crossover takes place after excitation into the singlet metal-to-ligand charge-transfer (MLCT) band. We found that the corresponding electronic states have their energy minimum in the same region as the low-spin (LS) state and that the energy dependence of the triplet MLCT states are nearly identical to the (1) MLCT states. The high-spin (HS) state is found to cross the MLCT band near the equilibrium geometry of the MLCT states. These findings give additional support to the hypothesis of a fast singlet-triplet interconversion in the MLCT manifold, followed by a (3)MLCT-HS ((5)T2) conversion accompanied by an elongation of the Fe-N distance.
已对 Fe(II)(bpy)3（bpy = 联吡啶）进行了从头算计算，以确定与光诱导激发态自旋捕获相关的电子态能量随 Fe-配体距离的变化。光诱导自旋交叉发生在激发到单重态金属-配体电荷转移（MLCT）带之后。我们发现，相应的电子态在与低自旋（LS）态相同的区域具有其能量最小值，并且三重态 MLCT 态的能量依赖性几乎与（1）MLCT 态相同。HS 态被发现靠近 MLCT 态的平衡几何结构穿过 MLCT 带。这些发现为 MLCT 多重态中快速单重态-三重态相互转换的假设提供了额外的支持，随后是（3）MLCT-HS（（5）T2）转换，同时伴随着 Fe-N 距离的延长。
