Temperature dependence of excitation energy transport in a benzene branching molecular system

The dynamics of excitation energy transport in a benzene centered branched molecule are presented. This system contains pyridine distrylbenzene (pyridine-DSB) chromophores attached to the benzene center giving the 1,3,5-tris((E)-2-{4-[(E)-2-pyridin-4-ylvinyl]phenyl}vinyl)-2,4,6-trimethylbenzene (T155) multi-chromophore system. Excitation energy transport was investigated by ultra-fast time resolved fluorescence anisotropy measurements. A depolarization time of similar to800 fs was observed at room temperature and the anisotropy decay time increased at lower temperatures while a new fast decay component appeared. The anisotropy decay residual value was found to decrease systematically with decreasing temperature. From consideration of both steady-state and time-resolved results it is found that the benzene branching center has excitations localized on pyridine-DSB chromophores at room temperature. The appearance of fast anisotropy decay component in addition to slow (similar to1 ps) component at low temperature suggests that energy transfer dynamics approaches the intermediate (crossover) characteristics of incoherent and coherent regimes. (C) 2003 Elsevier B.V. All rights reserved.