5,5′-bridged bis(1,2,3-dithiazoles):: Spin states and charge-transfer chemistry

Bifunctional 1,2,3-dithiazoles bridged with azine and phenylenediamine spacers have been prepared, with a view to determining the extent of communication between the two dithiazole rings as a function of the electronic and steric demands of the bridge. The crystal structure of the closed-shell diazine derivative [S2NClC2=NN=C2C-S-2] is rigorously planar. Cyclic voltammetry on this compound indicates two reversible one-electron oxidations. The radical cation state has been characterized by EPR spectroscopy and by crystal structure determination of its 1:1 PF6- salt. The latter reveals little interaction between neighboring radical cations; consistently, the material exhibits a conductivity of sigma < 10(-5) S cm(-1). Insertion of a phenylene group into the diazine bridge to afford [S2NClC2=NC6H4N=C2ClNS2] leads to significant torsional motion between the phenylene ring and the two end groups, as a result of which the two DTA rings are electronically independent; no radical cation state has been observed for this species. Crystal data for Cl2S4N4C4: a = 5.1469(15), b = 13.343(2), c;= 14.2031(17), orthorhombic, Pbca, Z = 4. Crystal data for Cl2S4N4C4PF6: a = 11.699(4), b = 12.753(5), c = 10.461(4), beta = 112.17(1)degrees monoclinic, C2/c, Z = 4. Crystal data for C12S4N4C10H4: a = 3.9477(6), b = 23.790(3), c = 7.3769(9), beta =90.793(12)degrees, monoclinic, P2(1)/c, Z = 2.