Theoretical Insights into Impact of Direct Transfer Coupling on Conductance Spectrum of Diradical Molecular Junction

Metal-free diradicals based on polycyclic aromatic hydrocarbons are promising materials for organic spintronics applications due to their low spin-orbit coupling and tunable spin interactions. However, the impact of direct transfer coupling between the two radical centers on the conductance spectrum remains unclear. In this study, we employ the hierarchical equations of motion method to simulate the inelastic electron transport through the Au/2-OS/Au junction (an open-shell molecule based on polycyclic aromatic hydrocarbon, denoted as 2-OS). By investigating the influence of a non-zero coupling between the singly occupied molecular orbitals, we find that the direct transfer coupling between the two radicals introduces an effective antiferromagnetic coupling, which is superimposed on the spin exchange coupling.