A novel sulfur-nitrogen Π-heterocyclic radical anion, (6H-1,2,3-benzodithiazo16-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 CrTo1(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, mu eff = 1.64 (mu B), indicates n-dimerization of 5 in the solid state. For the molar magnetic susceptibility x of 8, the temperature dependences of xT and 1/ x in the range 2-300 K can be approximated by the Curie-Weiss law with the Curie-Weiss constant C and temperature 1', equal to 0.33 0.01 cm3 K mo1-1 and -1.0 0.1 K, respectively. In the mean-field approximation, the effective value of the exchange interaction of [CrTol(2)]C with its neighboring cations can be estimated as 41= -1.4 cm-1. All the experimental results were supported by DFT calculations. (C) 2014 Elsevier Ltd. All rights reserved.