Spin, charge and lattice correlation in thiazyl radicals and their molecular compounds

We examined the crystal structures and magnetic properties of heterocyclic thiazyl radicals and their molecular compounds. 1,3,5-Trithia-2,4,6-triazapentalenyl (TTTA) exhibited a room-temperature bistability between a paramagnetic high-temperature (HT) phase and a diamagnetic low-temperature (LT) phase. The phase control of TTTA was achieved by pressure and light irradiation. The conductivity of TTTA in the HT phase (10−8 Ω−1 cm−1) was increased by five orders of magnitude due to I2 doping. 1,3,2-Benzodithiazolyl (BDTA) also made a diamagnetic–paramagnetic phase transition above room temperature, but fresh samples always exhibited superheating and supercooling at the transition. The molecular compounds, TTTA·[Cu(hfac)2], BDTA·[Ni(mnt)2] and (Benzo[1,2-d:4,5-d′]bis[1,3,2]dithiazole (=BBDTA))·MCl4 (M = Ga and Fe) were found to include rather strong ferromagnetic interactions.