Energy transfers in weakly interacting oligothiophenes

The optical properties of oligothiophene inclusion compounds in perhydrotri phenylene are reported. Excitonic effects are suppressed due to the large i nter-molecular distances imposed by the host crystal. In a mixture of quinq uethiophene and terthiophene inclusion compounds we observe very efficient long range energy transfers from the short to the long oligomer. Foerster t heory indicates that quite large critical distances are involved in this sy stem, thanks to the parallel relative orientation of the molecules within t he channels of the host crystal. The fast rise times (shorter than 40 ps) o f quinquethiophene excited state population, observed with time-resolved ph otoluminescence studies, suggest the presence of sizeable contributions fro m energy transfers among terthiophene molecules. (C) 2001 Elsevier Science B.V. All rights reserved.