Experimental and Theoretical Studies on 1,4,5,7-Dithiadiazepinyl Radicals: Preparation and X-ray Structure of 5-(Trimethylsilyl)tetrachlorobenzo-1,4,5,7-dithiadiazepine

1,4,5,7-Dithiadiazepinyl radicals and their selenium analogs have been studied by density functional theory calculations. Compared to 1,2,3,5-dithiadiazolyls, this novel family of 9 pi-electron radicals is predicted to have low disproportionation and dimerization energies, properties that are advantageous for the preparation of molecular conductors. The radical [CH(3)C(6)H(3)S(2)N(2)C(C(6)H(4)CH(3)-4)](*)() (5a) was generated in solution by the cyclocondensation reaction of CH(3)C(6)H(3)(SCl)(2) with 4-CH(3)C(6)H(4)CN(2)(SiMe(3))(3) followed by treatment with PhSeCl. The ESR spectrum of 5a consists of a slightly asymmetric quintet (g = 2.0070 and A(N)(iso) = 4.9 G). The N-(trimethylsilyl)-substituted was characterized by X-ray crystallography: monoclinic, P2(1)/a, a = 12.585(3) Å, b = 12.211(2) Å, c = 14.003(2) Å, beta = 101.86(2) degrees, V = 2106.0(7) Å(3), and Z = 4. Polycyclocondensation reactions and thermal instability toward elimination of nitriles hamper the isolation of pure samples of the radicals.