Sensitized reactions by benzophenones in the higher triplet excited state

Transient behaviors of benzophenone (BP) and several substituted benzophenones in the higher triplet excited state (Tn,n>2) were investigated by two-color two-laser excitation technique. Energy transfer from BP(Tn) to quenchers (Q) having higher ET1 than that of BP and the second energy transfer from Q(T1) to BP(S0) were observed. The lifetime of BP(Tn) is estimated to be 450 ps which is long enough for a bimolecular reaction to occur. The decay of Q(T1) depended on the concentration and structure of the Q. BP(Tn)-sensitized cleavages of C–Cl bond of CCl4 and C–Br bond of bromobenzene occurred.