Iodine charge-transfer salts of bis(1,2,3,5-diselenadiazolyl) diradicals; solid-state characterization of the thiophene-bridged derivative [(Se2N2C)C4H2S(CN2Se2)][I]
by Cordes, A. Wallace; Haddon, Robert C.; Hicks, Robin G.; Oakley, Richard T.; Vajda, Kristen E.
Electroreduction of the 2,5-thiophene-bridged bis(1,2,3,5-diselenadiazolylium) salt [T-2,5-Se][SbF6](2) in acetonitrile, at a Pt wire and in the presence of iodine, affords a highly conductive (sigma = 10(2) S cm(-1) at 293 K) 1:1 charge-transfer (CT) salt [T-2,5-Se] [I], the crystal structure of which has been determined by single-crystal X-ray diffraction. The crystals belong to the orthorhombic space group Fm2m, a = 3.544(2), b = 10.9808(16), c = 31.464(5) Angstrom, V= 1224.5(7) Angstrom(3). The structure consists of perfectly superimposed pi-stacks of molecular units bridged by columns of disordered iodines. This packing motif is similar to that of the related 1,3-benzene-bridged derivative [1,3-Se] [I], but the lateral intermolecular Se ... Se interactions linking adjacent pi-stacks are considerably shorter, indicative of a more isotropic electronic structure for [T-2,5-Se][I]. Magnetic susceptibility measurements on [T-2,5-Se][I] nonetheless indicate a phase transition to a diamagnetic state near 200 K, behaviour similar to that observed for [1,3-Se][I]. The electronic structures and transport properties of the two compounds are discussed in the light of extended Huckel band-structure calculations.
- Canadian Journal of Chemistry-Revue Canadienne de Chimie
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- 1480-3291; 0008-4042