Steady-state fluorescence-based investigation of the interaction between protected thiols and gold nanoparticles

The first demonstration of thioester and thiocarbonate binding to gold is provided via steady-state fluorescence spectroscopy of probe molecule adsorption onto a nanoparticle surface. Both thioester I and thiocarbonate 2 bind noncovalently to gold from aqueous solution, with 2 possessing a greater affinity for the gold surface relative to 1. The surface-bound molecules assemble into high packing densities comprising molecular footprints of 24.5 +/- 1.0 Angstrom(2) per molecule. Both 1 and 2 deprotect catalytically on the gold surface to yield hydrolysis products and surface-bound thiolate. This process is thermally activated and can be described by an Arrhenius-type expression with activation energies of 14.0 and 16.7 kcal/mol for I and 2, respectively. The results presented herein demonstrate the role of gold in catalyzing thioester and thiocarbonate hydrolysis and diversify the synthetic repertoire of organosulfur functional groups that can be used for binding to gold.