Rates of Quenching and Hydrogen Abstraction of Benzophenone Triplet with Cumene and Oligostyrenes

Abstract

ABSTRACT:Rate constants of quenching, kq, and hydrogen abstraction, k., of benzophenone triplet with oligostyrenes from dimer to hexamer as well as with cumene were determined in acetonitrile at 30oC from transient phosphorescence decay and· quantum yield for benzophenone reduction measurements. The values of kq =(4.0± 1.0) x 10 6 unit-M-1 s-1 and k. =(1.3 ±0.3) x 10 5 unit-M-1 s-1 for oligostyrenes are independent of the number of monomer unit, n. The kq for oligostyrene is three times larger than kq for cumene, its monomer model, supposingly due to a: sandwich-type encounter of benzophenone with two adjacent phenyl groups, but k. for oligostyrene is equal to k. for cumene. The chemical reaction (hydrogen abstraction) contributes in only to total deactivation of benzophenone triplet by oligostyrenes.