Strong coupling in macrocyclic thiophene investigated by time-resolved two-photon excited fluorescence

We report the feratosecond dynamics of fluorescence anisotropy excited through the two-photon absorption (TPA), which provides direct signatures of delocalized electronic excitations for symmetrical macromolecular architectures. Two-photon excited fluorescence anisotropy is strongly correlated with the orientation and value of the transition moment from the excited state to the second and higher lying states. For macromolecular systems it leads to a relatively low initial fluorescence anisotropy and specific femtosecond anisotropy dynamics. We have experimentally demonstrated qualitatively different anisotropy dynamics for twoand one-photon absorption excitations for strongly coupled ring architecture prospective for artificial-lightharvesting applications and possessing an enhanced TPA-absorption cross section. (c) 2007 Optical Society of America.