Prototypal Dithiazolodithiazolyl Radicals:  Synthesis, Structures, and Transport Properties

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 char...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2003-11, Vol.125 (47), p.14394-14403
Main Authors: Beer, Leanne, Britten, James F, Brusso, Jaclyn L, Cordes, A. Wallace, Haddon, Robert C, Itkis, Mikhail E, MacGregor, Douglas S, Oakley, Richard T, Reed, Robert W, Robertson, Craig M
Format: Article
Language:English
Subjects:
Chemistry
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Free radicals chemistry
Heterocyclic compounds
Organic chemistry
Organic compounds
Physics
Reactivity and mechanisms
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
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Summary: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 π-stacks of undimerized radicals, with many close intermolecular S- - -S contacts. Magnetic, conductivity, and optical measurements have been perfomed and the results interpreted in light of extended Hückel band calculations. The crystalline materials are paramagnetic above 100 K, with room-temperature conductivities σRT 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.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja0371350