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

(6 H -1,2,3-benzodithiazol-6-ylidene)malononitrilidyl ( 5 ) was generated electrochemically and chemically, and characterized by solution EPR in combination with UV–Vis spectroscopy. The salt [CrTol 2 ] + [ 5 ] was isolated and characterized by elemental analysis, solution and solid-state EPR and by magnetic measurements in the temperature range 2–300 K. (6 H -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 π-dimerization of 5 in the solid state. For the molar magnetic susceptibility χ 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 сm −1 . All the experimental results were supported by DFT calculations.