Through-space conjugated molecular wire comprising three π-electron systems

A [2.2]paracyclophane-based through-space conjugated oligomer comprising three π-electron systems was designed and synthesized. The arrangement of three π-conjugated systems in an appropriate order according to the energy band gap resulted in efficient unidirectional photoexcited energy transfer by the Förster mechanism. The energy transfer efficiency and rate constants were estimated to be >0.999 and >10(12) s(-1), respectively. The key point for the efficient energy transfer is the orientation of the transition dipole moments. The time-dependent density functional theory (TD-DFT) studies revealed the transition dipole moments of each stacked π-electron system; each dipole moment was located on the long axis of each stacked π-electron system. This alignment of the dipole moments is favorable for fluorescence resonance energy transfer (FRET).