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Crystals 2012, 2(3), 1092-1107; doi:10.3390/cryst2031092
Article

Synthesis, Structures and Properties of Molecular Conductors Based on Bis-Fused Donors Composed of (Thio)Pyran-4-ylidene-1,3-dithiole and Tetraselenafulvalene

, , , *  and *
Department of Applied Chemistry, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama 790-8577, Japan
* Authors to whom correspondence should be addressed.
Received: 27 April 2012 / Revised: 10 July 2012 / Accepted: 17 July 2012 / Published: 9 August 2012
(This article belongs to the Special Issue Molecular Conductors)
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Abstract

Bis-fused donors composed of (thio)pyran-4-ylidene-1,3-dithiole and tetraselenafulvalene (1a, 2a) and their bis(methylthio) derivatives (1b, 2b) were synthesized. Cyclic voltamograms of all the donors consisted of four pairs of one-electron redox waves, and it was suggested that a positive charge of 1+• and 2+• distributed mainly on the (thio)pyran-4-ylidene-1,3-dithiole moiety. X-ray structure analysis revealed that (1b)PF6(C6H5Cl)0.5 and (2b)PF6(C6H5Cl) formed one-dimensional conducting stacks in which the donors were dimerized or tetramerized. In those salts, intramolecular charge disproportionation of the donors was suggested by X-ray structure analysis and density functional theory (DFT) calculation with UB3LYP/6-31G(d) basis function. A tight-binding band calculation suggested that these materials were band insulators. All the donors gave highly conducting TCNQ (7,7,8,8-tetracyanoquinodimethane) complexes and I3 salts (σrt = 0.3–19 S cm−1 on a compressed pellet) with very low activation energies of 0.017–0.040 eV, while single crystals of (1b)PF6(C6H5Cl)0.5 and (2b)PF6(C6H5Cl) exhibited semiconductive behavior with large activation energies (Ea = 0.16–0.22 eV).
Keywords: molecular conductor; tetrathiapentalene; pyran; thiopyran; tetraselenafulvalene; cyclic voltammetry; X-ray structure analysis; band calculation; electrical conductivity; intramolecular charge disproportionation molecular conductor; tetrathiapentalene; pyran; thiopyran; tetraselenafulvalene; cyclic voltammetry; X-ray structure analysis; band calculation; electrical conductivity; intramolecular charge disproportionation
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Ishidzu, K.-I.; Ashizawa, M.; Watanabe, M.; Shirahata, T.; Misaki, Y. Synthesis, Structures and Properties of Molecular Conductors Based on Bis-Fused Donors Composed of (Thio)Pyran-4-ylidene-1,3-dithiole and Tetraselenafulvalene. Crystals 2012, 2, 1092-1107.

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