Charge-Transfer Quenching of Triplet α-Trifluoroacetophenones

Article abstract of DOI:10.1021/ja00532a031

The effects of ring substituents and of aromatic quenchers on the photoreduction by toluene of α,α,α-trifluoroacetophenone (AF3) have been measured.A plot of log k_CT vs. ionization potential of the donor indicates that ΔG<*>_CT equals 22percent ΔG for the full electron transfer.A corresponding plot of log k_CT vs. the triplet state reduction potential of ring-substituted AF3's, if analyzed as linear, would indicate that there is no intrinsic difference in reactivity between n,?^* and ?,?^* triplets but would also indicate that ΔG<*>_CT equals 42percent ΔG.The discrepancy between the 22 and 42percent is suggested to involve differing reactivities of n,?^* and ?,?^* triplets.If n,?^* triplets are substantially more reactive, the plot vs. triplet reduction potential is expected to curve upward as the equilibrium population of n,?^* triplet increases with substitution.