Kinetics-energetics relationship during the electron transfer from trivalent phosphorus compounds to the singlet photoexcited sensitizers

The rate constants k(ET) for the electron transfer [ET) from trivalent phosphorus compounds Z(3)P to the singlet photoexcited states S-1* of neutral sensitizers, i.e., 9,10-dicyanoanthracene (DCN) and 9-cyanoanthracene (CA), were determined based on the Stern-Volmer (SV) method. As previously found in the ET from Z(3)P to the singlet photoexcited states S-1(+)* of a monocationic sensitizer, i.e., rhodamine 6G (Rho(+)), the plot of logk(ET) versus the free-energy change of the ET step, AGO, in the endothermic region deviated upward from the line predicted by the Rehm-Weller theory. The deviation was slightly greater during the ET to S-1* than during the ET to S-1(+)*. Copyright (c) 2008 John Wiley & Sons, Ltd.