TRANSIENT ABSORPTION AND RESONANCE RAMAN INVESTIGATION OF THE PHOTOCHEMICAL REACTIVITY OF 2,2'-BIPYRIMIDINE IN SOLUTION

The 248-nm photolysis products of 2,2'-bipyrimidine (22BPMY) and of its per-deuterated analogue in various organic solvents have been investigated by transient UV/visible absorption and time-resolved resonance Raman spectroscopies in the nano/microsecond time scale. Reduction of the lowest triplet state via electron abstraction from amines and via hydrogen atom abstraction from hydrogen-donating solvents is evidenced. The conformations of four transient species involved in the reactivity, the tripler state, the anion radical, the H-adduct radical and its protonated form, the dihydro cation radical, are discussed from the detailed analysis of the resonance Raman spectra. A very short-lived Raman spectrum detected on electron transfer is ascribed to an ion pair. The existence of this ion pair is in agreement with the relative kinetic behaviors of the different transient species involved in the reaction.