The measurement of an electron transfer reaction in a non-polar supercritical fluid

The intermolecular electron transfer reaction between a biphenyl anion and pyrene in supercritical ethane was studied using pulse radiolysis. Second-order electron transfer rates were found to be of the order of 1011 M−1 s−1. The rate constants appear to be approximately constant over the pressure range 55–133 bar. Two possibilities are discussed that could explain the present results: solvent clustering, or a dependence of the solvent reorganization energy on pressure. Reorganization energies of non-polar supercritical ethane were estimated from the observed rate constant using the modified Marcus equation.