Photoinduced electron transfer in jet cooled molecular complexes

Exciplex and excimer formation have been probed in several jet cooled compl exes using mass selective two-photon ionisation and fluorescence excitation spectroscopy as well as ground state depletion spectroscopy (hole burning) : (i) In the anthracene-dimethyl-ortho-toluidine system, it has been found that the ionisation step takes place with a much higher efficiency from the charge transfer state responsible for the exciplex emission than from the locally excited state giving rise to the resonant fluorescence. (ii) The di mer, trimer, and higher clusters of anthracene all show only excimer emissi on. When compared to the dimer, the trimer exhibits a peculiar behaviour (s tructured fluorescence excitation and hole burning spectra, short lifetime and low ionisation efficiency) which has been related to a significant loca lly excited character of the initially prepared state of the species excite d state. (iii) The influence of an intermolecular hydrogen bond bn the elec tron transfer process has been studied in the 2,2,2-trifluoro-1-(9-anthryl) ethanol-dimethylaniline system. A threshold for exciplex formation higher t han in the case of the anthracene-dimethylaniline complex is observed.