TY - JOUR AU - Vauthey, E. AU - Hoegemann, C. AU - Allonas, X. TI - Direct Investigation of the Dynamics of Charge Recombination Following the Fluorescence Quenching of 9,10-Dicyanoanthracene by Various Electron Donors in Acetonitrile PY - 1998 JF - Journal of Physical Chemistry A JA - J. Phys. Chem. A SN - 1089-5639 VL - 102 IS - 38 SP - 7362 EP - 7369 L1 - http://pubs.acs.org/doi/pdf/10.1021/jp981367h L2 - http://pubs.acs.org/doi/full/10.1021/jp981367h L3 - http://dx.doi.org/10.1021/jp981367h M3 - 10.1021/jp981367h UR - http://dx.doi.org/10.1021/jp981367h N2 - The dynamics of the intermediate generated upon diffusional electron transfer (ET) quenching of 9,10-dicyanoanthracene by electron donors of varying oxidation potential in acetonitrile has been investigated using several transient grating techniques. With most of the donor/acceptor pairs studied, the transient grating spectrum cannot be differentiated from those of the free ions. Exciplex fluorescence, with the same lifetime as that of the ion pair, is observed with all donors. To extract from the measured kinetics the rate constant of exciplex dissociation, kEXdia , and of back ET, kEXBET , within these exciplexes, three different schemes have been considered. The best agreement is obtained by assuming that charge recombination predominantly takes place within the exciplex. The obtained kEXBET values are substantially different from the BET rate constants deduced indirectly from the free-ion yields and with a donor-independent rate constant of separation. For each class of donors, kEXBET exhibits a logarithmic free energy dependence with a slope of about −2 eV-1. Moreover, kEXdia is not constant but increases continuously with diminishing donor\'s oxidation potential. ID - 98 ER -