Cationic Diradicals Derived from Non-Aufbau Radicals toward Magnetoluminescence and Qubit Applications.

Control over the spin and electronic structures of radicals and diradicals is essential for advancing magnetically responsive optoelectronics and quantum information technologies. Here, we elucidate an electronic structural distinction between cations derived from Aufbau- and non-Aufbau-type radicals through quantum chemical calculations. It shows that the oxidation of Aufbau-type radicals yields closed-shell singlet cations, whereas non-Aufbau-type radicals generate cationic diradicals with nearly degenerate singlet and triplet ground states (S and T). Guided by molecular-orbital energetics, we establish a design principle for creating such cationic diradicals via oxidation of radicals consisting of strongly electron-donating donors and electron-withdrawing radical acceptors. We introduce the parameter to quantify the magnetic field required for S-T resonance (magnetoluminescence suitability) and the η parameter to assess spin selectivity for qubit applications. These descriptors provide valuable guidance for future high-throughput screening of materials for magnetoluminescence and qubit applications.