Regioselectivity in the photodimerization of 9-hydroxy-methylanthracene and 9-anthracene carboxylic acid esters in surfactant systems

Abstract

Photodimerization of n-alkyl esters of 9-anthracene carboxylic acid was carried out in micellar and vesicular solutions to investigate the influence of the length of the ester chain (C 4–C 12) on the ratio Dht/Dhh of formation of the two isomeric products (head-to-tail and head-to-head dimer). With increasing chain length the relative yield of the head-to-head dimer increases. For 9-hydoxymethylanthracene the temperature dependence of regioselectivity in photodimerization was investigated in diethylether, methanol, methylcyclohexane, acetonitrile, and vesicular solutions as solvents. In organic solvents the ratio Dht/Dhh increases with decreasing temperature. In vesicular solution a minimum of the ratio at around 30 °C was found corresponding to a gel-to-liquid-crystal phase transition of the vesicles, which was independently determined by electron spin resonance spectroscopic spin probe technique.