Temperature Dependence of Regioselectivity and Excimer Equilibrium in the Photodimerization of 9-Methylanthracene

Abstract

The temperature dependence of the ratio of formation of the two isomeric products (head-to-tail- and head-to-head-photodimer) of the photodimerization of 9-methylanthracene was measured in chloroform, ethanol, diethyl ether, and methylcyclohexane as solvents. The ratio increases or decreases with temperature depending on the solvent. One of the isomeric photoproducts was converted photochemically into the other one, indicating an equilibrium of excimer precursors of the products.