BIRADICAL SPIN DYNAMICS WITH DISTANCE-DEPENDENT EXCHANGE INTERACTION AND ELECTRON-TRANSFER EFFICIENCY

The spin dynamics and reaction kinetics of photogenerated zwitterionic biradicals of the type 2A-(CH2)n2D+ (n = 8, 9, 10) are described for a model which assumes the same AD distance dependence for a "through space" exchange interaction and for the efficiency of electron back-transfer to the singlet ground state 1A(CH2)n1D and to a triplet excited state 3A*(CH2)n1D. The model is independent of the length n of the polymethylene chain and accounts well for the three type of observation on the biradicals: the mono-exponential character of the biradical decay, the life time associated with this decay, and the magnetic field dependence of the yield of the triplet excited state. © 1990.