Surface-induced symmetry reduction in molecular switching: asymmetric cis–trans switching of CH3S-Au-SCH3 on Au(111)

Abstract

The cis–trans isomerization of CH₃S-Au-SCH₃ driven by the tip of the scanning tunneling microscope is investigated at 77 K. CH₃S-Au-SCH₃ anchored on the Au(111) surface with the S–Au–S axis parallel to the substrate functions as a molecular switch due to the flipping of the CH₃ groups. The bonding between CH₃S-Au-SCH₃ and Au(111) leads to asymmetric isomerization where one of the two methyl groups flips much more effectively than the other, despite the symmetry of CH₃S-Au-SCH₃. Our findings suggest the possibility of constructing similar molecular switches that can be operated at room temperature and a potential route for fine-tuning of molecular switches in future nanoscale electro-mechanical devices.