2.2]Paracyclophane-based single molecular wire consisting of four π-electron systems

Abstract

A [2.2]paracyclophane-based through-space–conjugated tetramer comprising four partially stacked π-electron systems was designed and synthesized, with a large overlap integral between the photoluminescence spectrum of the terminal π-electron system of the through-space–conjugated trimer and the absorption band of the fourth π-electron system. Efficient unidirectional photoexcited energy transfer in the tetramer occurred by the Förster mechanism; the energy transfer efficiency and related rate constants were found to be >0.999 and >1012 s–1, respectively, and stepwise energy transfer was found to be dominant. The [2.2]paracyclophane-based tetramer acted as a single molecular wire for efficient unidirectional photoexcited energy transfer.