Single-Ion Magnetism of the [Dy(hfac)] Anions in the Crystalline Semiconductor {TSeT}[Dy(hfac)] Containing Weakly Dimerized Stacks of Tetraselenatetracene.

The oxidation of tetraselenatetracene (TSeT) by tetracyanoquinodimethane in the presence of dysprosium(III) tris(hexafluoroacetylacetonate), Dy(hfac), produces black crystals of {TSeT}[Dy(hfac)] () salt, which combines conducting and magnetic sublattices. It contains one-dimensional stacks composed of partially oxidized TSeT molecules (formal averaged charge is +2/3). Dimers and monomers can be outlined within these stacks with charge and spin density redistribution. The spin triplet state of the dimers is populated above 128 K with an estimated singlet-triplet energy gap of 542 K, whereas spins localized on the monomers show paramagnetic behavior. A semiconducting behavior is observed for with the activation energy of 91 meV (measured by the four-probe technique for an oriented single crystal). The Dy ions coordinate four hfac anions in [Dy(hfac)], providing symmetry. Slow magnetic relaxation is observed for Dy under an applied static magnetic field of 1000 Oe, and is a single-ion magnet (SIM) with spin reversal barrier = 40.2 K and magnetic hysteresis at 2 K. Contributions from Dy and TSeT paramagnetic species are seen in EPR. The Dy ion rarely manifests EPR signals, but such signal is observed in . It appears due to narrowing below 30 K and has = 6.1871 and = 2.1778 at 5.4 K.