Quantum Spin Transport Through Blatter's Diradicals and Triradicals.

A single unpaired electron in an organic molecule residing in the singly occupied molecular orbital (SOMO) renders it an organic radical. It incorporates exchange splitting in the frontier occupied and unoccupied orbitals, separating the α- and β-orbitals. This fact enormously impacts the electron transport properties in organic radicals by promoting spin-polarized current and significantly enhancing conductance compared to their closed-shell counterparts. Exploring these phenomena, several monoradicals have been investigated through molecular spintronic experiments and theories. In this work, we addressed the impact of an increasing number of radical centers on the transport properties of multiradical molecular species by considering di- and triradicals based on a stable Blatter's radical. With an increasing number of radical centers, the number of SOMOs increases. Does the increased number of frontier SOMOs provide larger exchange splitting and better transport properties? Here, we observed that the spatial distributions of SOMOs and their coupling with electrodes play a decisive role compared with the presence of multiple unpaired electrons in the molecular systems.