Single-Ion Magnetism of the [Dy III (hfac) 4 ] - Anions in the Crystalline Semiconductor {TSeT 1.5 } ●+ [Dy III (hfac) 4 ] - Containing Weakly Dimerized Stacks of Tetraselenatetracene.

The oxidation of tetraselenatetracene (TSeT) by tetracyanoquinodimethane in the presence of dysprosium(III) tris(hexafluoroacetylacetonate), Dy ^III (hfac) ₃ , produces black crystals of {TSeT _1.5 } ^●+ [Dy ^III (hfac) ₄ ] ^- ( 1 ) 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 1 with the activation energy of 91 meV (measured by the four-probe technique for an oriented single crystal). The Dy ^III ions coordinate four hfac ^- anions in [Dy ^III (hfac) ₄ ] ^- , providing D _2d symmetry. Slow magnetic relaxation is observed for Dy ^III under an applied static magnetic field of 1000 Oe, and 1 is a single-ion magnet (SIM) with spin reversal barrier U _eff = 40.2 K and magnetic hysteresis at 2 K. Contributions from Dy ^III and TSeT ^●+ paramagnetic species are seen in EPR. The Dy ^III ion rarely manifests EPR signals, but such signal is observed in 1 . It appears due to narrowing below 30 K and has g ₄ = 6.1871 and g ₅ = 2.1778 at 5.4 K.