Is there a specific correlation between conductance and molecular aromaticity in single-molecule junctions?

Abstract

By using the first-principles method, conductance of molecular junctions containing one of five-atom cyclic unit cyclopentadiene, furan, and thiophene connected to two gold electrodes via different kinds of anchoring groups is theoretically investigated. The numerical results reveal that the experimental finding of negative relationship between conductance and molecular aromaticity (NRCA rule) does not always hold, and it is affected by the molecular anchoring group and contact manner between the molecule and electrodes. When the thiol or methylene anchoring group is used, NRCA rule is proved valid. However, this rule is not applicable for the case where isocyanide end group is used. Moreover, for methylene as the anchoring groups, it is found that the NRCA rule becomes invalid when the contact manner between the molecule and electrodes is changed from a cross style to a parallel one. The results are understood in terms of the molecular projected self-consistent Hamiltonian states as well as transmission spectra. This work facilitates the deep understanding of experimental observation from the theoretical point of view and is helpful for rational design of functional molecular devices.