First-principles study of electronic structures, magnetic properties, ultrafast spin dynamics, and spin logic gates in cobalt-π-bowl complexes.

We present a first-principles investigation of the geometries, energy levels, magnetic properties, spin dynamics, and spin logic gates in Co(C20H10)+ and (C5H5)Co(C20H10) complexes. For each structure, the most stable geometry, which corresponds to a quintet state, exhibits the Co atom positioned on the convex face of a hexagonal carbon ring within the C20H10 molecule. The many-body ground and excited states of the two structures are calculated, and their level distributions and spin localization are analyzed. The inclusion of spin-orbit coupling and an external magnetic field lifts the degeneracy of the triplet terms, producing substate splittings of 0.006∼0.051 eV and correspondingly shrinking the energy gaps while preserving the overall level distribution. The localization results show that a reversible spin-crossover scenario can be achieved within the subpicosecond regime in each structure. For the neutral complex with C5H5 attached, the states exhibit various types of spin-density and charge-density distributions, thus facilitating simultaneous spin(-flip)-transfer and charge-transfer scenarios, with the fastest process being completed within 80 fs. Based on them, reversible SWAP and CNOT logic gates are constructed. These investigations enrich our understanding of the influence of ligands on electronic structures and magnetic properties of Co-π-bowl systems, and provide valuable insights into designing suitable molecules for spin manipulation and developing reversible spin-logic gates for next-generation spintronic applications.