Magnetic exchange coupling of chalcogen-centered radicals mediated via the 2D curved π-network: A broken-symmetry approach

DFT broken-symmetry calculations framework at the B3LYP/6-31G(d) level were carried out to evaluate the magnetic exchange coupling constants of four chalcogen-centered radical-C60 diadducts. The interactions of radicals, including (O) over dotH, (S) over dotH, (S) over dotCH(3), (S) over dotC(6)H(5) occurred in different relative positions. The calculated exchange coupling constants indicate that the coupling interaction regime changes when the radical centers and the relative distance of binding sites on C60 coupler change. In fact, the most intense ferromagnetic interaction occurs when radicals form a right-angle with the fullerene center. The shapes of singly occupied molecular orbital (SOMO) and spin density distribution of structures have also been studied. The energy splitting of the singly occupied molecular orbitals (DESS) confirm the broken symmetry results. The calculated isotropic hyperfine coupling constants (hfccs) show some differences in diradical-coupler complexes that can be employed in the experimental electron paramagnetic resonance (EPR) spectroscopy. (C) 2016 Elsevier B.V. All rights reserved.