Non-Photoisomerizable Butterfly Shaped Tetrasubstituted Azobenzenes: Synthesis and Photophysical Studies

Abstract

The trans-azobenzene (AB) substituted derivatives with bulky carbazole (1), phenothiazine (2), and phenyl (3) have been synthesized to understand the effect of steric crowding around the –N[double bond, length as m-dash]N– linkage on the photoisomerization process. The substituents maintain orthogonality to the azobenzene plane and the electronic properties exhibit a combination of individual chromophores. Irradiation of 1 and 2 with various light sources including a 365 nm pen-ray lamp, and a 150 W Xe–Hg lamp, and even exposure to sunlight for a week does not yield the cis isomer revealing the exceptional photostability of the synthesized azobenzene derivatives. These studies suggest that possessing steric crowding around the azo linkage would be a potential strategy to develop photostable azobenzene-based functional materials.