The family of recently described salts based on the electron donor CNB-EDT-TTF (5-cyanobenzene-ethylenedithio-tetrathiafulvalene) and different anions A, with general formula (CNB-EDT-TTF)₄A, constitutes an unprecedented type of molecular conductor based on a bilayer structure of the donors. The crystal structures of the bilayer conductors (CNB-EDT-TTF)₄A with small discrete anions are reviewed and analyzed considering previously reported compounds with different anions (A = I₃⁻, ClO₄⁻, BF₄⁻, ReO₄⁻, PF₆⁻ and SbF₆⁻), as well as three new members of this family described here with AsF₆⁻, AuI₂⁻and I₂Br⁻. A common structural feature of this family of compounds is the head-to-head arrangement of the donors, induced by a network of weak CN⋯H–C interactions, which can be described as an effective combination of R²₂(10) and R²₄(10) synthons, forming donor bilayers alternating with anionic layers. The magnitude of the interactions associated with R²₂(10) and R²₄(10) synthons is estimated to be 4.7 and 10.0 kcal mol⁻¹, respectively. In spite of the common donor bilayer arrangement, a rich diversity of structural variations and polymorphs is observed. These structures are related to different types of donor or anion arrangements, which are analyzed. For all anions a β′′-type packing pattern of the donor molecules arranged in virtually identical bilayers is observed. However, for (CNB-EDT-TTF)₄I₃, so far a unique exception in this family of compounds, a distinct κ-type packing of the donors, is also obtained as a metastable phase as shown also by DFT calculations that predict the κ-phase above the β′′-phase. Another type of polymorphism is observed in β′′-(CNB-EDT-TTF)₄A, compounds with tetrahedral anions, related to the tilting of the donor molecules (either alternating or uniform) in successive bilayers, leading to monoclinic or triclinic unit cells, with doubling of one cell parameter corresponding to the thickness of one bilayer (∼25 Å). Finally, the anions, which often appear with fractional site occupation factors, can be ordered in the anionic plane, with different degrees of correlation between successive anion planes as shown in the AsF₆.compound. The implications of these structural features in the electronic properties of these compounds are also discussed.

中文翻译：

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导电双层盐（CNB-EDT-TTF）4A中的结构多样性

最近描述的基于电子给体CNB-EDT-TTF（5-氰基苯-乙撑二硫-四硫富瓦烯）和具有通式（CNB-EDT-TTF）₄ A的不同阴离子A的盐家族，构成了前所未有的分子导体类型基于供体的双层结构。双层导体的晶体结构（CNB-EDT-TTF）₄ A和小的离散阴离子被审查和分析考虑与不同阴离子先前报道的化合物（A = I ₃ ^-，CLO ₄ ^-，BF ₄ ^-，REO ₄ ^- ，PF ₆ ^-和的SbF ₆ ^-），以及该家族的三个新成员ASF这里描述₆ ^-，AUI ₂ ^-和我₂溴^- 。该化合物家族的共同结构特征是供体的头对头排列，这是由弱的C N⋯H-C相互作用网络引起的，可以说是R ² ₂的有效组合（10）和R ² ₄（10）合成子，形成与阴离子层交替的供体双层。与R ² ₂（10）和R ² ₄（10）合成子相关的相互作用的大小估计为4.7和10.0 kcal mol ^-1， 分别。尽管有常见的供体双层排列，但观察到结构变化和多晶型物的丰富多样性。这些结构与供体或阴离子排列的不同类型有关，需要进行分析。对于所有阴离子，观察到以实际上相同的双层排列的供体分子的β''型堆积模式。但是，对于（CNB-EDT-TTF）₄ I ₃，到目前为止，在该化合物家族中，作为供体的亚稳相也获得了供体的独特κ型堆积，这也是DFT计算得出的， β′相上方的κ相。在β''-（CNB-EDT-TTF）_4中观察到另一种多态性A，具有四面体阴离子的化合物，与供体分子在连续双层中的倾斜（交替或均匀）有关，导致单斜晶或三斜晶的晶胞，其中一个细胞参数的倍数对应于一个双层的厚度（约25Å） ）。最后，通常以分数位占据因子出现的阴离子可以在阴离子平面中排序，连续的阴离子平面之间的相关程度不同，如AsF ₆化合物所示。还讨论了这些结构特征对这些化合物的电子性质的影响。