[Mg 3 @C 20 ] + : an s-orbital electron spin system protected in carbon ring framework

Abstract

Increasing the proportion of s-orbital character and employing rigid ligands with zero nuclear spin can effectively suppress spin-orbit coupling, electron spin-nuclear spin hyperfine coupling, and spin-lattice vibrational coupling. This is crucial for designing electron spin-based two-level states molecular qubits. In this paper, we investigated the electronic structure, magnetic properties of Mg3+ cluster embedded C20 ring ([Mg3@C20]+) using density functional theory (DFT) and complete active space self-consistent field (CASSCF) method. The presence of an unpaired electron located on Mg3 cluster. The Mg−Mg metal−metal bonds exhibit substantial covalent character. The s-orbital of Mg3 cluster contributes 67% to the spin density. Nearly isotropic g-factors, nearly isotropic hyperfine structure coupling parameters, and a relatively narrow single peak in the EPR spectrum reveal‌ that the unpaired electron is an s-orbital nature‌. The s-orbital electron spin system, protected by the carbon ring, exhibits an interesting model system for electron spin-based two-level states.