title: Following the azide-alkyne cycloaddition at the silica/solvent interface with sum frequency generation.
abstract: The Cu(I) -catalyzed 1,3-dipolar azide-alkyne cycloaddition (CuAAC) has arisen as one of the most useful chemical transformations for introducing complexity onto surfaces and materials owing to its functional-group tolerance and high yield. However, methods for monitoring such reactions in situ at the widely used silica/solvent interface are hampered by challenges associated with probing such buried interfaces. Using the surface-specific technique broadband sum frequency generation (SFG), we monitored the reaction of a benzyl azide monolayer in real time at the silica/methanol interface. A strong peak at 2096 cm(-1) assigned to the azides was observed for the first time by SFG. Using a cyano-substituted alkyne, the decrease of the azide peak and the increase of the cyano peak (2234 cm(-1) ) were probed simultaneously. From the kinetic analysis, the reaction order with respect to copper was determined to be 2.1, suggesting that CuAAC on the surface follows a similar mechanism as in solution.
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2 (Canada).
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Li
authors.forename: Champika N
authors.initials: CN
authors.lastname: Weeraman
authors.forename: Julianne M
authors.initials: JM
authors.lastname: Gibbs-Davis
keywords: copper-catalyzed reactions; cycloaddition; interfaces; sum frequency generation; surface click chemistry