A theoretical study on charge transfer and other properties induced by conformation conversion of ligands in Ru complexes

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The second row transition metal complexes show higher covalency than the first row transition metal complexes, and exhibit chemically interesting properties. In this study, we take complexes including Ru which is equivalent to Fe and investigate electronic structures of primarily [Ru(III)L_5NO]^<2->, and Ru_3O(CH_3CO_2)_6L_2CO. These materials have been paid special attention in the field of transition metal complexes and tried to develop them in the biological or electronics as well as subject of fundamental studies. These types of complexes show unique properties induced by charge transfer and conformation conversion of ligands.[Ru(III)L_5NO] (L=CN^-) ; The crystal of this complex has two extremely long-lived photo-induced meta stable states. This is expected to be a promising switching material. In this study, we took [Fe(III)L_5NO] as well as [Ru(III)L_5NO] and studied the structure of the ground state and two meta stable states, and barrier heights among them, using ab initio calc … More ulations. Further more global excited state potential surfaces were calculated and explained possible photo induced isomerization among the meta stable and ground states by non-adiabatic transition. The high covalency in Ru complex cause higher potential barrier than in Fe complex and it is the origin of the longer life-time in Ru complex than in Fe complex.Ru_3O (CH_3CO_2)_6L_2CO (L=bzpy) ; We reported the electronic structure of [Ru_3O(CH_3CO_2)_6(bzpy)_2CO]^n (n=-2〜0, bzpy=4-benzoylpyridine) and relative stability of the isomers, using results of ab initio molecular orbital calculations. Recently, Tanaka et al. reported that the complex, Ru_3O(CH_3CO_2)_6L_2CO, shows six one-electron reversible redox processes. In their work, two slightly different C-O vibrational frequencies were obtained only for the 2 electron reduction species of this complex in CH_2Cl_2 solution, whereas only one C-O vibrational mode in the other species. This suggests that there exists two types of isomers in doubly reduced one. In the present calculation, we found the global minimum at the dihedral angle between the Ru_3-O plane and bzpy plane was almost 90° (perpendicular). The planer structure (0, 180°) was the local minimum. For the 2 electron reduction species, there were two minima at a planer structure and a perpendicular structure whose total energies are close to one another. This seems to explain the two C-O different vibrational modes. Less