Conformational changes of cyclohexanethiol adsorbed on gold surfaces

The conformational changes of cyclohexanethiol (CHT) on gold nanoparticles and gold plate surfaces were investigated by means of surface-enhanced Raman scattering. The equatorial chair conformer appeared to be dominant at high bulk concentrations, whereas, both the equatorial and axial chair conformers of CHT were found to exist at low bulk concentrations corresponding to a near monolayer coverage limit. Molecular-scale scanning tunneling microscopy imaging revealed the existence of two axial and equatorial conformers in the CHT monolayer on an Au(1 1 1) surface as well as the existence of the meta-stable conformer, which may be due to dynamic conformational changes of the cyclic ring. It was also found that the peaks corresponding to the axial bands disappeared below room temperature, indicating the equatorial conformer is dominant at low temperatures. From this result, we found that the conformation of CHT on an Au surface was easily changed by surface temperature.