Photochemical behaviour of matrix-isolated salicylaldehyde and its derivatives. Trapping of a non-hydrogen-bonded conformer

Abstract

The photochemical behaviour of salicylaldehyde, its 3-, 4-, and 5-methoxy derivatives, 2′- hydroxyacetophenone (7), and methyl salicylate (8) have been investigated in argon, xenon, nitrogen, and carbon monoxide matrices. Non-hydrogen-bonded conformers of salicylaldehyde and methoxysalicylaldehydes were generated using u.v. light (λ_max. 250 or 300 nm interference filters) and trapped in all matrices that were investigated. New conformers of methyl salicylate (8) and 2′-hydroxyacetophenone (7) are not formed in rare-gas matrices or in solid nitrogen. The data support a model in which the host cage hinders internal rotation of the acetyl and methoxycarbonyl groups of (7) and (8) respectively, in inert gas and nitrogen matrices.