Dipolar excitonic states of oligo-anthrylenes

Photoexcitation of dimeric, trimeric, and tetrameric oligomers of anthracene in benzene results in the formation of relaxed S 1 excitonic states with dipole moments of 6.9, 8.0, and 9.1 D respectively. Dipole reversal occurs with a relaxation time in the range of 8 ′ 2 ps and is driven by a combination of fluctuations in the solvent environment and torsional motion about the central sigma bonds. The excitonic interaction at any given moment in time involves mainly only two neighboring anthracene moieties rather than delocalization over all chromophoric units.