Theoretical determination of electronic properties of resorcinol and hydroquinone as building blocks of molecular wires

Abstract

This study presents a theoretical and computational analysis of resorcinol and hydroquinone as potential molecular wire components, employing the tight-binding Hamiltonian formalism within a real-space decimation approach based on Green’s functions. We investigated their electronic transport properties, specifically electrical current and conductance, by varying key parameters such as the atomic site energy, the coupling energy, and the electrode attachment configurations. We found a semiconductor behavior in both molecules, reaching their maximum electron capacity at around 5 V. In addition, we analyzed the substituent patterns of hydroxyl groups on the aromatic ring by comparing the results of both molecules. Our findings highlight the critical influence of the aromatic ring’s inner coupling energy and the hydroxyl groups’ atomic site energy on electronic transport. The strong inner coupling regime in the aromatic ring demonstrated better transmission probability in accordance with the aromatic sp² hybridization moiety. Due to the disubstitution pattern in resorcinol, the coupling between the hydroxyl groups and the aromatic ring plays a crucial role in electron conductance in this system, as demonstrated by the diminishing the polarization of electrons from the hydroxyl to the aromatic ring by the weakening of the energy coupling. Notably, we observed a stark contrast between the two molecules: resorcinol, characterized by meta-disubstitution, exhibits quantum interference effects, while hydroquinone, with para-disubstitution, facilitates a more stable and efficient electronic flux. Interestingly, comparing our results with those of previously reported aromatic conductors, such as benzene and catechol, we found that for both systems (i.e., resorcinol, hydroquinone), the voltage threshold is lower, with hydroquinone a particularly promising system, reaching I/I₀ = 0.45 at V = 1.2 V, almost doubling the values of all the other compared systems. These results showcase resorcinol and hydroquinone as promising candidates for molecular wire applications in electronic devices.