Two photon absorption properties of bis(n-carbazolyl)-poly-phenylenes

We studied the two phc,ton absorption (TPA) properties of conjugated, symmetric bis(N-carbazolyl)-di-phenylpolyenes and bis(N-carbazolyl)-tri-phenylpolyenes. These novel molecules relate to the family of bis-donor-di-phenylpolynene recently shown [1] to possess very high two-photon absorption and fluorescence coefficients. The symmetric substitution of carbazole end-groups enhances the photostability of the molecules and at the same time maintains high TP coefficients (delta (max) > 1000 GM) as determined from two-photon fluorescence measurements with picosecond pulse excitation. A blue shift of the linear absorption and a red shift of the TP peak reflect a larger proximity of the one and two photon states in carbazole substituted chromophores. High fluorescence quantum yield (0.6-0.8) was found in most of the molecules studied. These results suggest that efficient and photo-stable TP chromophores with carbazole donors are promising materials for applications in two-photon imaging and sensitization. (C) 2000 Elsevier Science S.A. All rights reserved.