The tripletlifetimes of hindered 4′-substituted-2,4,6-tri-isopropylbenzophenones decrease (increase) with the increasing electron-donating (withdrawing) ability of the ring substituents; this is the opposite effect to that expected from the rate of the intermolecular hydrogen-abstraction reaction of unhindered benzophenones.
Absorption kinetics of photochemical reactions of 2,4,6-triisopropylbenzophenone and its derivatives in benzene at room temperature studied by nanosecond spectroscopy. 2. Laser chemistry, molecular dynamics, collisions, and energy transfer