Laser flash photolysis studies on the induced-quenching process competing with hydrogen atom abstraction of triplet benzophenone. Heavy atom effect

The rate constants (kHA and kIQ) for the hydrogen atom abstraction (HA) and induced-quenching (IQ) processes between triplet benzophenone (3BP∗) and halogenated toluenes (XTL) were determined by means of nanosecond laser flash photolysis techniques. It was found that the kIQ value increased proportionally with increasing the squared summation of the spin-orbit coupling constant (ζ) of atoms involved in XTL while the kHAʹs were almost indifferent. It was demonstrated that the IQ process was the intersystem crossing process which was induced mainly by the spin-orbit interaction between 3BP∗ and XTL.