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

(6H-1,2,3-Benzodithiazol-6-ylidene)malononitrile (4) was electrochemically and chemically reduced with tetrakis(dimethylamino)ethylene (TDAE) and CrTol2 into the title radical anion (5). The electrochemically generated 5 and its salts [TDAE]2+[5]2 (7) and [CrTol2]+ [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, μeff = 1.64 μB, 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 Tc equal to 0.33 ± 0.01 cm3 K mol−1 and −1.0 ± 0.1 K, respectively. In the mean-field approximation, the effective value of the exchange interaction of [CrTol2]+ with its neighboring cations can be estimated as zJ = −1.4 сm−1. All the experimental results were supported by DFT calculations.

(6H-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 [CrTol2]+[5] was isolated and characterized by elemental analysis, solution and solid-state EPR and by magnetic measurements in the temperature range 2–300 K.Figure optionsDownload as PowerPoint slide