Photochemistry and Surface Properties of Self-Assembled Monolayers of cis- and trans-4-Cyano-4'-(10-thiodecoxy)stilbene on Polycrystalline Gold

Herein we describe a self-assembled array in which a photochemical reaction within a monolayer results in modification of the surface properties. Irradiation of an ordered monolayer of cis-4-cyano-4'-(10-thiodecoxy)stilbene (1) on a gold surface with visible light ([ge] 350 nm) results in a decrease in the contact angle with water in the irradiated region. Significantly, irradiation of a monolayer of the trans isomer (2) under identical conditions does not result in any change in contact angle. When the sample is cooled so that atmospheric moisture condenses on the native and isomerized surfaces, these differences can easily be followed by the naked eye; thus, irradiation constitutes a new technique for surface imaging and for differentiation of surface composition. The results demonstrate that photoisomerization of 1 may be used to photopattern a self-assembled monolayer on a gold surface. Significantly, changes in the contact angle with water are achieved in the monolayer without any contacting reagent or solvent during the irradiation and without any treatment afterward. 22 refs., 3 figs.