A layered organic conductor θ-(ET)₄CdI₄(PhCl) has been synthesized and characterized (ET is bis(ethylenedithio)tetrathia-fulvalene). It belongs to the family of dual-layered conductors θ-(ET)₄MBr₄(C₆H_6−nX_n) and for the first time includes the iodine-containing anion [CdI₄]²⁻. It exhibits metallic conductivity within the plane of organic ET molecules down to 206 K, and semiconductor properties in the perpendicular direction. The temperature dependence of in-plane resistivity for the compound shows changes in the conductive properties at 199 K and below 164 K. Structural phase transitions have been revealed at these temperatures. Crystal structures determined at 220, 185, and 100 K are attributed to tetragonal, monoclinic, and triclinic crystal systems, respectively. As a result of the structural phase transition at 199 K, equivalent ET layers become nonequivalent, the dihedral angles between ET molecules of neighboring stacks change, and ordering of terminal ethylene groups of ET molecules occurs in a half of radical cation layers. At 100 K, the difference between neighboring radical cation layers increases as compared with the monoclinic phase and the ordering of terminal ethylene groups in all ET molecules has been found. The solvent molecule PhCl remains disordered in all these structures.

中文翻译：

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含碘双层导体θ-（ET）4CdI4（PhCl）冷却时的相变

已经合成并表征了层状有机导体θ-（ET）₄ CdI ₄（PhCl）（ET为双（亚乙基二硫代）四硫富富烯）。它属于双层导体θ-（ET）₄ MBr ₄（C ₆ H _{6- n} X _n）的族，并且首次包含含碘的阴离子[CdI ₄ ] ^2-。它在低至206 K的有机ET分子平面内显示出金属导电性，并在垂直方向上显示出半导体特性。该化合物的面内电阻率与温度的关系显示出在199 K和164 K以下时导电特性的变化。在这些温度下发现了结构相变。在220、185和100 K下确定的晶体结构分别归因于四方晶系，单斜晶系和三斜晶系。由于在199 K发生结构相变，等效的ET层变得不等价，相邻堆叠的ET分子之间的二面角发生变化，并且ET分子的末端亚乙基在有一半的阳离子层中发生排序。在100 K，与单斜相相比，相邻自由基阳离子层之间的差异增加，并且已发现所有ET分子中末端亚乙基的顺序。溶剂分子PhCl在所有这些结构中保持无序。