New spiropyrans based on 1,3-benzoxazine-2-one: acid catalyzed synthesis and theoretical insight into the photochromic activity

Abstract

A new series of spiropyrans based on 1,3-benzoxazine-2-one were synthesized using acid catalysis. Contrary to expectations, 6′-bromo-6-chloro-3-methyl-8′-nitro-spiro[1,3-benzoxazine-4,2′-chromene]-2-one and 6,6′-dichloro-3-methyl-8′-nitro-spiro[1,3-benzoxazine-4,2′-chromene]-2-one did not exhibit photochromic behavior, which was explained by TD DFT calculations to be a consequence of the existence of an effective non-radiative decay pathway allowing the structural relaxation of the spiropyrans in the first singlet excited state.