Ab Initio MO Studies on Polysilane Oligomer Radical Anions as Model Molecules of Polysilane Radical Anions

Abstract

Polysilane oligomer radical anions with up to six Si atoms have been theoretically investigated as model molecules of high polymer polysilane radical anions by ab initio MO theory. According to the calculated results, the polysilane oligomer radical anions can exist as bound anions having a σ-type ground state with an unpaired electron occupying a Si−Si antibonding σ* orbital. They are stabilized with an increase in the Si−Si main chain length both in terms of the boundness of an unpaired electron and bonding strength. The π-type states, on the other hand, exist as excited states for these oligomer radical anions. The calculated results strongly suggest that polysilane radical anions with a π-type ground state are hardly generated regardless of their molecular size and geometry. The Si 3d orbital contributions in the ground and excited states of the polysilane radical anions, such as dπ−dπ conjugations, have also been investigated.