Energy redistribution dynamics in triarylamine–triarylborane containing hexaarylbenzenes

Abstract

Two hexaarylbenzenes (HAB) 1 and 2 each decorated by three triarylamines (TAA) as electron donors and three triarylboranes (TAB) as electron acceptors in a symmetric (1) and asymmetric (2) fashion as well as one model compound (3) with only one donor–acceptor pair were investigated by ultrafast transient absorption and fluorescence upconversion spectroscopy. Fluorescence anisotropy measurements revealed energy redistribution between localised, partly relaxed CT-states of the HABs 1 and 2 induced by dipole–dipole interaction with energy transfer time constants of ca. 3 ps. These results manifest symmetry breaking in the formally symmetric HAB 1 upon photoexcitation.