Singlet Exciton Delocalization and Localization in Oligosilanes

摘要

The aim of this thesis is to reproduce and interpret the trends in electronic absorption and emission spectra of permethylated oligosilanes by theoretical means. Longstanding questions concerning the structures responsible for various emissions from electronically excited singlet states that have been observed are addressed. New deactivation mechanisms that allow oligosilanes to return to ground state equilibrium geometries are also presented. The question of how saturated systems accommodate sigma-sigma* excitation is addressed computationally. Finally, new bonding patterns in excited states of oligosilanes have been identied. These include large geometry distortions from the ground state equilibrium structures, rehybridization, and in some cases the involvement of 4s, 4p and 3d Si atomic orbitals results in pentavalent Si for special cases where electronic excitation becomes highly localized.