A novel sulfur-nitrogen p-heterocyclic radical anion, (6H-1,2,3-benzodithiazol-6-ylidene)malononitrilidyl, and its homo- and heterospin salts

摘要

(6H-1,2,3-Benzodithiazol-6-ylidene)malononitrile (4) was electrochemically and chemically reduced with tetrakis(dimethylamino)ethylene (TDAE) and CrTol_2 into the title radical anion (5). The electrochemically generated 5 and its salts [TDAE]~(2+)[5]_2 (7) and [CrTol_2]~+ [5] (8) were characterized by solution EPR in combination with UV-Vis spectroscopy. Salts 7 and 8 were isolated and characterized by elemental analysis and solid-state EPR, and 8 by magnetic measurements in the temperature range 2-300 K. The value of the effective magnetic moment of the salt 8 at 300 K, μ_(eff) = 1.64 μ_B, indicates p-dimerization of 5 in the solid state. For the molar magnetic susceptibility v of 8, the temperature dependences of χT and 1/ χ in the range 2-300 K can be approximated by the Curie-Weiss law with the Curie-Weiss constant C and temperature T_c equal to 0.33 ± 0.01 cm~3 K mol~(-1) and -1.0 ± 0.1 K, respectively. In the mean-field approximation, the effective value of the exchange interaction of [CrTol_2]~+ with its neighboring cations can be estimated as zJ = -1.4 cm~(-1). All the experimental results were supported by DFT calculations.