Direct measurements of energy transfer between identical chromophores in solution

Abstract

The rate of intramolecular electronic excitation energy transfer in 9,9′ bifluorene has been investigated in a variety of solvents, using both time-correlated single photon counting and femtosecond fluorescence upconversion technique. The kinetics of energy transfer were determined in both cases by time dependent fluorescence anisotropy measurements. The energy transfer dynamics between fluorene moieties has been found to occur on a time scale of approximately 600 fs in different solvents and has been correlated with the T2 value calculated from the absorption linewidth and the β value obtained from jet measurements. The dihedral angle between the fluorene moieties was also calculated from the anisotropy measurement and compared with the values obtained from a solution phase NMR determination.