An Alternating -Stacked Bisdithiazolyl Radical Conductor
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- 作者：Alicea A. Leitch ; Robert W. Reed ; Craig M. Robertson ; James F. Britten ; Xueyang Yu ; Richard A. Secco ; Richard T. Oakley
- 刊名：Journal of the American Chemical Society
- 出版年：2007
- 出版时间：June 27, 2007
- 年：2007
- 卷：129
- 期：25
- 页码：7903 - 7914
- 全文大小：1475K
- 年卷期：v.129,no.25(June 27, 2007)
- ISSN：1520-5126
文摘
A general synthetic route to the resonance-stabilized pyrazine-bridged bisdithiazolyl framework,involving the reductive deprotection of 2,6-diaminopyrazine-bisthiocyanate and cyclization with thionylchloride, has been developed. An N-methyl bisdithiazolyl radical, 4-methyl-4H-bis[1,2,3]dithiazolo[4,5-b:5',4'-e]pyrazin-3-yl, has been prepared and characterized in solution by electron paramagnetic resonancespectroscopy and cyclic voltammetry. Its crystal structure has been determined at several temperatures.At 295 K, the structure belongs to the space group Cmca and consists of evenly spaced radicals 
-stackedin an alternating ABABAB fashion along the x-direction. At 123 K, the space group symmetry is lowered byloss of C-centering to Pccn, so that the radicals are no longer evenly spaced along the -stack. At 88 K,a further lowering of space group symmetry to P21/c is observed. Extended Hückel Theory band structurecalculations indicate a progressive opening of a band gap at the Fermi level in the low-temperature structures.Magnetic susceptibility measurements over the range 4-300 K reveal essentially diamagnetic behaviorbelow 120 K. Variable-temperature single-crystal conductivity (
) measurements indicate that the conductivityis activated, even at room temperature, with a room-temperature value RT = 0.001 S cm-1 and a thermalactivation energy Eact = 0.19 eV. Under an applied pressure of 5 GPa, RT is increased by 3 orders ofmagnitude, but the conductivity remains activated, with Eact being lowered to 0.11 eV at 5.5 GPa.
-stackedin an alternating ABABAB fashion along the x-direction. At 123 K, the space group symmetry is lowered byloss of C-centering to Pccn, so that the radicals are no longer evenly spaced along the -stack. At 88 K,a further lowering of space group symmetry to P21/c is observed. Extended Hückel Theory band structurecalculations indicate a progressive opening of a band gap at the Fermi level in the low-temperature structures.Magnetic susceptibility measurements over the range 4-300 K reveal essentially diamagnetic behaviorbelow 120 K. Variable-temperature single-crystal conductivity () measurements indicate that the conductivityis activated, even at room temperature, with a room-temperature value RT = 0.001 S cm-1 and a thermalactivation energy Eact = 0.19 eV. Under an applied pressure of 5 GPa, RT is increased by 3 orders ofmagnitude, but the conductivity remains activated, with Eact being lowered to 0.11 eV at 5.5 GPa.