Electronic Structure of Metallocene-based Polymers

Abstract

The band structures of metallocene-based polymers in which the nearest metalloecenes were directly linked by a C-C bond have been determined by employing the tight-binding crystal orbital (CO) method. In particular, we determined the band structures of metallocene-based alternate copolymers whose metal sequences in a unit cell were Fe-Co, Fe-Fe-Co-Co, Fe-Ni, Ru-Co and Os-Co. The band structures of alternate copolymers of Fe-Co and Fe-Ni possessed a partially occupied (PO) band whose crystal orbitals were extremely localized at the 3d orbitals of cobalt or nickel atom. Alternate copolymers of Ru-Co and Os-Co had the same tendency as that of band structure of Fe-Co. Therefore, it was clear that the band structures of the metallocene-based alternate copolymers were considered to be a superposition of the polymetallocenylenes. Furthermore, we examined the effect of inserting the bridging part of boron-, phosphorus-, and sulfur bridges between the nearest ferrocenes upon the band structures of ferrocene-based polymers. The electronic structure of the boron-bridged polymer was similar to that of the silicon-bridged polymer whose band structure was determined in our previous study. On the other hand, the phosphorus- and sulfur-bridged polymers yielded two degenerated HO bands whose COs were localized at P or S 2p orbitals.