Trans-cis isomerization of arylether dendrimers with azobenzene core and terminal hydroxy groups

Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Ji-hye LeeEun Ju Shin

Abstract

Azobenzene-cored arylether dendrimers 2a-2c with polar hydroxy groups at the periphery have been prepared from hydroboration-oxidation reaction of azobenzene-cored arylether dendrimers 1a-1c with nonpolar vinyl groups at the periphery. Trans-->cis photoisomerization of central azo group has been investigated by UV-vis spectral changes after photolysis. The results show that dendrimers 1a-1c and 2a-2c in methanol/dichloromethane (1/1, v/v) have carried out trans-cis isomerization. Reaction rate for trans-->cis photoisomerization of 2a-2c with polar hydroxy groups increases with increasing generation upon irradiation of 350 nm. On the other hand, the reaction rate of cis-->trans thermal back isomerization for 2a-2c decreases with increasing the generation. This result is somewhat different from that for 1a-1c with nonpolar vinyl groups. Both the reaction rates of trans-->cis photoisomerization and cis-->trans thermal back isomerization for 1a-1c decrease in higher generation.

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