Theoretical Interpretation of Conductivity Measurements of a Thiotolane Sandwich. A Molecular Scale Electronic Controller

Quantum density functional theory and classical molecular dynamics studies of tolane molecules are carried out to interpret results of conductivity measurements on a monolayer of thiotolane molecules self-assembled on a gold surface and sandwiched by a titanium layer. Density functional theory techniques have been used to determine the ground state conformations and electronic structure, while classical molecular dynamics accounts for the effects of pressure and temperature for a cluster of five thiotolane molecules arranged between titanium and gold surfaces used to simulate the experimental system. On the basis of the theoretical results, it can be concluded, in agreement with the experimental findings, that the relative angle between two benzene rings in each tolane molecule determines its conductivity, with a maximum at 0° and a minimum at 90°. Therefore, this system would work as an unbiased controller, where the current through the molecule is controlled by the angle of one phenyl ring with respect to the other.