Beer Leanne, Brusso Jaclyn L, Haddon Robert C, Itkis Mikhail E, Kleinke Holger, Leitch Alicea A, Oakley Richard T, Reed Robert W, Richardson John F, Secco Richard A, Yu Xueyang
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
J Am Chem Soc. 2005 Dec 28;127(51):18159-70. doi: 10.1021/ja055122b.
A synthetic sequence to salts of N-alkylated pyridine-bridged 1,2,3-thiaselenazolo-1,2,3-thiaselenazolylium cations [2]+ (R1 = Me, Et; R2 = H) is described. The corresponding radicals 2 (R1 = Me, Et; R2 = H) can be generated from the cations by chemical or electrochemical reduction. Crystals of the two radicals are isostructural and consist of interpenetrating pi-stacked arrays of closed-shell Se-Se sigma-bonded dimers [2]2 laced together with numerous short intermolecular Se- - -Se, Se- - -S, and Se- - -N contacts. Variable-temperature magnetic, conductivity, and near-infrared optical measurements indicate that the bulk materials behave as small band gap semiconductors with room-temperature conductivities sigma(RT) near 10(-6) S cm(-1) and thermal activation energies Ea of 0.32 eV (R1 = Me) and 0.36 eV (R1 = Et). LMTO band structure calculations on both compounds are consistent with this interpretation. The application of external pressure leads to dramatic increases in conductivity; at 4 GPa sigma(RT) reaches a value near 10(-1) S cm(-1) for R1 = Me and 10(-2) S/cm for R1 = Et. The conductivity remains activated for both compounds, but for R1 = Me the activation energy Ea is reduced to near 0.03 eV at 5 GPa, suggestive of a weakly metallic state.
描述了一种合成N-烷基化吡啶桥连的1,2,3-噻硒唑并-1,2,3-噻硒唑鎓阳离子[2]+（R1 = 甲基，乙基；R2 = 氢）盐的序列。相应的自由基2（R1 = 甲基，乙基；R2 = 氢）可通过化学或电化学还原从阳离子生成。这两种自由基的晶体结构相同，由闭壳层Se-Se σ键合二聚体[2]2的相互贯穿的π堆积阵列组成，这些阵列通过大量短程分子间Se---Se、Se---S和Se---N接触连接在一起。变温磁性、电导率和近红外光学测量表明，块状材料表现为小带隙半导体，室温电导率σ(RT)接近10(-6) S cm(-1)，热激活能Ea分别为0.32 eV（R1 = 甲基）和0.36 eV（R1 = 乙基）。对这两种化合物的LMTO能带结构计算与这种解释一致。施加外部压力会导致电导率急剧增加；在4 GPa时，对于R1 = 甲基，σ(RT)达到接近10(-1) S cm(-1)的值，对于R1 = 乙基，σ(RT)达到10(-2) S/cm。两种化合物的电导率仍保持激活状态，但对于R1 = 甲基，在5 GPa时激活能Ea降至接近0.03 eV，表明处于弱金属态。
