Photophysics of linked donor—acceptor systems: through-space and through-bond interactions

Abstract

Possible competition between through-σ-bond and through-space interaction on the one hand and between through-σ-and through-π-bond interaction on the other has been studied in flexibly and rigidly linked donor—acceptor systems. In a first part, pyrenyl-substituted donor—acceptor compounds were studied, where a permethylated oligosilane chain acts as a flexible spacer. The possible involvement of a sigma delocalized oligosilane chain in the electron transfer process is studied. Intramolecular electron transfer was observed from a permethylated hexasilane chain towards pyrene in the excited state. Through-space ground-state interactions were observed for the donor—acceptor substituted hexamethyl trisilane chain. In order to study the electron transfer process via through-σ-and through-π-bond interactions, rigid trichromophoric compounds in an A 1—D—A 2 configuration were studied. One of the acceptors is directly bound to the donor moiety, while the other acceptor is separated from the donor by a rigid spacer of three sigma bonds. The study of these compounds by means of absorption, stationary and time-resolved emission spectroscopy reveals a competition between the two possible electron transfer directions in one of the trichromophoric compounds.