Multi-Dimensional Crystal Structures and Unique Solid-State Properties of Heterocyclic Thiazyl Radicals and Related Materials

Abstract

Abstract The crystal structures and magnetic properties of heterocyclic thiazyl radicals and related materials have been examined. TTTA (=1,3,5-trithia-2,4,6-triazapentalenyl) exhibited a first-order phase transition between a paramagnetic high-temperature (HT) phase and a diamagnetic low-temperature (LT) phase, with a wide thermal hysteresis loop over the temperature range 230–305 K. The phase control of TTTA was achieved by pressure and by light irradiation. BDTA (=1,3,2-benzodithiazolyl) also exhibited a diamagnetic–paramagnetic phase transition above room temperature. However, fresh samples always exhibited a superheating of the LT phase that resulted in a double melting (melt–recrystallization–melt process) and supercooling of the HT phase, which in turn led to an antiferromagnetic ordering at 11 K. The molecular compounds of thiazyl radicals were prepared; TTTA formed a coordination polymer structure in the TTTA·[Cu(hfac)2 (=bis(hexafluoroacetylacetonato)–copper(II))] crystal, where a ferromagnetic coupling was found between the organic and inorganic species. The cation radical salts, [BBDTA (=benzo[1,2-d:4,5-d′]bis[1,3,2]dithiazole)]·MCl4 (M = Ga and Fe), exhibited ferromagnetic ordering at 7 K and ferrimagnetic ordering at 44 K after evaporation of crystal solvents. We also grew crystals of M–TTDPz (TTDPz = tetrakis(thiadiazole)porphyrazine and M = H2, Fe, Co, Ni, Cu, and Zn) and performed their structural analyses. Their crystal structures were found to depend strongly on the central metal ion and could be classified into three forms: α, β, and γ.