Electron transfer in a donor-substituted acridinium dye: evidence for dynamical solvent control

Time-resolved emission is used to explore the intramolecular excited-state electron transfer in a donor-substituted acridinium dye in a variety of sol vents at room temperature. Emission decays are predominantly bi-exponential , with the faster of the two time constants being a good measure of the cha rge transfer time. In 14 high-polarity solvents this time is correlated to the solvation times previously measured with the solvation probe Coumarin 1 53 via an apparent power law, tau(LE --> CT) approximate to 8.4[tau](solv)( 0.65). In solvents less polar than acetone the times observed deviate widel y from this relationship, probably due to the effects of ion pairing. (C) 1 999 Elsevier Science B.V. All rights reserved.