The Synthesis of Difluoro and Dimethyl Derivatives of 2,6-Bis(dicyanomethylene)-2,6-dihydro-4<i>H</i>-cyclopenta[2,1-<i>b</i>:3,4-<i>b</i>′]dithiophen-4-one (CPDT-TCNQ) and the Conducting Properties of the Metallic Salts Based on the Dimethyl Derivative
作者:Takehiro Chonan、Kazuko Takahashi
DOI:10.1246/bcsj.77.1487
日期:2004.8
In order to investigate how the sheet-like network along the side-by-side direction constructed by the strong inter-column S···N and O···H atom–atom contacts influences the stability of the metallic state of novel one-dimensional metallic anion radical salts of 2,6-bis(dicyanomethylene)-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b′]dithiophen-4-one (CPDT-TCNQ), the 3,5-difluoro (F2CPDT-TCNQ) and 3,5-dimethyl (Me2CPDT-TCNQ) derivatives of CPDT-TCNQ, not possessing hydrogen atoms at the 3,5-positions to construct the inter-column O···H contacts, have been synthesized. The anion radical salts, Me4X(Me2CPDT-TCNQ)2 (X = P and As), showed a metallic temperature dependence of the resistivity from room temperature down to around 240 K and 200 K, respectively, whereas Me4X(Me2CPDT-TCNQ)2 (X = N and Sb) were semiconducting. The metal–insulator transition temperatures (TMI) of Me4X(Me2CPDT-TCNQ)2 (X = P and As) are significantly higher than those of MX4(CPDT-TCNQ)2 (X = P and As). Moreover, the extent of destabilization of the metallic state is much more significant in Me4N(Me2CPDT-TCNQ)2, since MeN4(CPDT-TCNQ)2 is metallic down to 130 K. Although electric conduction can not occur along the side-by-side direction in either salt of CPDT-TCNQ and Me2CPDT-TCNQ, these facts suggest that the two-dimensional sheet-like molecular network along the a-axis may contribute to stabilize the one-dimensional metallic states of the anion radical salts of CPDT-TCNQ.
为了研究柱间S--N和O--H原子的强接触所构建的并排方向的片状网络如何影响2,6-双(二氰基亚甲基)-2,6-二氢-4H-环戊二烯并[2,1-b:我们合成了 2,6-双(二氰基亚甲基)-2,6-二氢-4H-环戊并[2,1-b: 3,4-b′]二噻吩-4-酮(CPDT-TCNQ)、CPDT-TCNQ 的 3,5-二氟(F2CPDT-TCNQ)和 3,5-二甲基(Me2CPDT-TCNQ)衍生物。阴离子自由基盐 Me4X(Me2CPDT-TCNQ)2(X = P 和 As)在室温至 240 K 和 200 K 左右的电阻率分别显示出金属温度依赖性,而 Me4X(Me2CPDT-TCNQ)2(X = N 和 Sb)则是半导体。Me4X(Me2CPDT-TCNQ)2(X = P 和 As)的金属-绝缘体转变温度(TMI)明显高于 MX4(CPDT-TCNQ)2(X = P 和 As)。此外,Me4N(Me2CPDT-TCNQ)2 中金属态的不稳定程度要显著得多,因为 MeN4(CPDT-TCNQ)2 在低至 130 K 时是金属态。虽然在 CPDT-TCNQ 和 Me2CPDT-TCNQ 的任何一种盐中都不能沿着并排方向导电,但这些事实表明,沿着 a 轴的二维片状分子网络可能有助于稳定 CPDT-TCNQ 阴离子自由基盐的一维金属态。