title: Prototypal dithiazolodithiazolyl radicals: synthesis, structures, and transport properties.
abstract: New synthetic routes to 1,2,3-dithiazolo-1,2,3-dithiazolylium salts, based on double Herz condensations of N-alkylated 2,6-diaminopyridinium salts with sulfur monochloride, have been developed. The two prototypal 1,2,3-dithiazolo-1,2,3-dithiazolyl radicals HBPMe and HBPEt have been prepared and characterized in solution by cyclic voltammetry and EPR spectroscopy. Measured electrochemical cell potentials and computed (B3LYP/6-31G) gas-phase disproportionation enthalpies favor a low on-site Coulombic repulsion energy U in the solid state. The crystal structures of HBPR (R = Me, Et) have been determined by X-ray crystallography (at 293 K). Both consist of slipped pi-stacks of undimerized radicals, with many close intermolecular S- - -S contacts. Magnetic, conductivity, and optical measurements have been performed and the results interpreted in light of extended Hückel band calculations. The crystalline materials are paramagnetic above 100 K, with room-temperature conductivities sigma(RT) of 10(-5)-10(-6) S cm(-1); the slightly greater conductivity of the R = Et compound can be associated with a more well developed band structure. We suggest a Mott-Hubbard insulator ground state for these materials, with an on-site Coulomb repulsion energy U of about 1.0 eV.
authors: Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors: Leanne
authors: L
authors: Beer
authors: James F
authors: JF
authors: Britten
authors: Jaclyn L
authors: JL
authors: Brusso
authors: A Wallace
authors: AW
authors: Cordes
authors: Robert C
authors: RC
authors: Haddon
authors: Mikhail E
authors: ME
authors: Itkis
authors: Douglas S
authors: DS
authors: MacGregor
authors: Richard T
authors: RT
authors: Oakley
authors: Robert W
authors: RW
authors: Reed
authors: Craig M
authors: CM
authors: Robertson