Identification of the light-absorbing states in tolane with potential relevance to self-similar phenylacetylene dendrimers

We report the observation and analysis of the high resolution fluorescence excitation spectrum of tolane (or diphenylacetylene, DPA) in a molecular be am. This analysis shows that the first one-photon-allowed state in DPA has B-1(1u) symmetry, a consequence of exciton-like coupling between the two La -1 states of the connected phenylacetylene, (PA) units. The resulting long- axis polarization of the B-1(1u)-(1)A(g) transition of each linear segment is responsible for the diverse optical properties of PA dendrimers. (C) 200 1 Elsevier Science BN. All rights reserved.