ELECTRONIC STRUCTURES OF LINEAR POLYSILANE RADICAL ANIONS FOR GROUND AND LOW-LYING EXCITED STATES - A THEORETICAL STUDY

摘要

MM2-molecular dynamics and semi-empirical PM3-MO calculations were performed on Linear polysilane oligomer radical anions. The electronic structures for the ground and low-lying excited states have been determined by means of the semi-empirical PM3-CI method. The permethyloligosilane radical anion [Si-n(Me)(2n+2)](-) (n = 6-20) was chosen as a model compound of the polysilane radical anion. The molecular dynamics calculation and the geometry optimization suggested that the regular all-trans chain was most stable for the polysilane radical anions. In all cases, an unpaired electron is occupied in an in-plane pi* (Si-Si) orbital and widely delocalized along the main Si-Si chain. The first excitation energy is gradually red-shifted as a function of number of chain Si atoms and the oscillator strength is increased. The band structure for polysilane radical anions is discussed on the basis of theoretical results. (C) 1997 Elsevier Science B.V. [References: 21]