分子导体θ-(ET)(C_7H_7SO_3)·3H_2O的合成、结构和导电性

Synthesis, Structure and Conductivity of Molecular Conductor θ-(ET)(C_7H_7SO_3)·3H_2O

用恒电流电化学结晶的方法合成了一种新的基于电子给体BEDT TTF(双亚乙基二硫四硫富瓦烯 )的电荷转移盐θ (ET) (C7H7SO3 )·3H2 O (ET为BEDT TTF的简写 ,C7H7SO-3 =对甲苯磺酸根 ) .用四圆X衍射的方法测定了θ (ET) (C7H7SO3 )·3H2 O的结构 .晶体属于三斜晶系 ,P 1空间群 ;a =0 8682 ( 1)nm ,b =1 2 0 2 7( 1)nm ,c =2 5 890 ( 3 )nm ,α =87 0 2 5 ( 6)° ,β =89 117( 8)° ,γ =69 0 71( 7)° ,V =2 5 2 16( 5 )nm3 ,R =0 0 5 80 .晶体中ET自由基沿a轴方向堆积成柱 ,相邻两个分子柱中的ET分子平面的夹角为 49 3 0° .在b轴方向存在着分子柱侧向间的S…S近距作用 .ET阳离子层与对甲苯磺酸根阴离子层沿c轴方向上交替排列 .位于阳离子层与阴离子层之间的许多H2 O形成了有利于晶体导电性的二维氢键网络 .θ (ET) (C7H7SO3 )·3H2 O在 ( 0 0 1)晶面上某方向上的室温导电率为 0 0 11S·cm-1,所测变温电导曲线表明 ,该晶体在 12 0～ 2 78K温度区间内表现为半导体导电行为 ,导电激活能Ea=0 3 16eV .从 2 78～ 2 86K表现为金属导电性 .在 2

A new ET-based radical salt, θ-(ET)(C 7H 7SO 3)·3H 2O (ET=bis(ethylenedithio)tetrathiafulvalene, C 7H 7SO - 3=p-toluenesulfonate anion), has been synthesized by oxidative electrocrystallization. The crystal structure was determined by four-circle X-ray diffraction. The crystal belongs to triclinic system, P-1 space group with the unit cell parameters: a=0.8682(1) nm, b=1.2027(1) nm, c=2.5890(3) nm, α=87.025(6)°, β=89.117(8)°, γ=69.071(7)°, V=2.5216(5) nm 3, R=0.0570. In the title crystal, the ET radicals are stacked to form columns along the a-axis and there is 49.30° dihedral angle between adjacent ET molecular planes. The inter-stack side-by-side S...S short contacts along the b-axis help to form a kind of cationic conducting sheet parallel to (001) plane. Layers of ET cations and layers of C 7H 7SO - 3 counter anions alternate to arrange along the c-direction. The H 2O molecules between the cationic sheet and the anionic sheet result in strong H-bond net which is beneficial to electrical conductivity. The room temperature conductivity at a certain direction on (001) plane of θ-(ET)(C 7H 7SO 3)·3H 2O crystal was measured to be 0.011 S·cm -1. From 120 to 278 K, the resistivity-temperature curve demonstrates its semiconductor behavior, with an activation energy of 0.316 eV. However, with a metal-semiconductor phase transition around 276 K, it exhibits metallic conductivity from 278 to 286 K.