Abstract The compound under study 7CBB consists of two biphenyl moieties A–B and C–D linked by a carboxylate group. Ring A terminates in a 4-cyano group and C–D is linked to the terminal alkyl chain. A previously reported room temperature determination of the crystal structure employing MoKα X-radiation was thought to contain serious errors in describing the alkyl chain as being disordered. The X-ray structure factors were not deposited with this published structure and as a consequence two new X-ray data sets have been collected: (1) using MoKα radiation at room temperature 295 K (a repeat of the previous study) and (2) using CuKα radiation at 150 K in an attempt, which proved successful, to improve the overall quality of the structure determination. The corrected MoKα structure and the CuKα structure both reported here have enabled the previous errors to be identified, concluding that there is no disorder in the alkyl chain. The alkyl chain in the MoKα structure at 295 K was found to have anisotropic thermal factors slightly exaggerated with respect to the remainder of the structure. However, this effect is not observed in the CuKα structure at 150 K, all anisotropic thermal factors including those in the alkyl chain being reduced to cover a much smaller overall range of values. Consequently, it can be concluded that the effect observed in the alkyl chain at 295 K is merely one of a thermal nature, not one of disorder. There are no unusual bond lengths or angles present. The biphenyl moieties are planar within 0.035 Å and 0.020 Å respectively. The dihedral angles of all ring pairs have been calculated. Calculation of intermolecular distances between molecules related by a centre of symmetry reveals the existence of a number of van-der Waals interactions. The H-bonding motif typical of crystal structures of cyanobiphenyl compounds is observed. The molecular packing mode corresponds to that of a precursor of the smectic phase. Graphic Abstract The alkyl chain thermal ellipsoids for 7CBB (a) the Mo RT structure are noticeably exaggerated compared to those for the remainder of the structure, an effect which is not present in (b) the Cu LT structure (Drawn with Ortep/Raster (Barnes in J Appl Cryst 30:568, 1997; Merritt and Bacon in Methods Enzymol 277:505–524, 1997)). It may be concluded therefore that in the Mo RT structure this is a thermal effect and cannot be explained in terms of static disorder.

中文翻译：

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极性烷基介晶化合物 7CBB 在 150 K 下的 X 射线结构：4-氰基联苯-4'-庚基联苯羧酸盐

摘要 研究中的化合物 7CBB 由两个联苯部分 A-B 和 C-D 组成，这些部分通过羧酸酯基团连接。环 A 终止于 4-氰基，C-D 连接到末端烷基链。先前报道的使用 MoKα X 辐射的晶体结构的室温测定被认为在将烷基链描述为无序时存在严重错误。X 射线结构因子没有与这个已发表的结构一起沉积，因此收集了两个新的 X 射线数据集：（1）在室温 295 K 下使用 MoKα 辐射（重复先前的研究）和（2 ) 尝试使用 150 K 的 CuKα 辐射来提高结构确定的整体质量，结果证明是成功的。此处报道的修正后的 MoKα 结构和 CuKα 结构使之前的错误得以识别，得出烷基链没有无序的结论。发现在 295 K 时 MoKα 结构中的烷基链具有相对于结构的其余部分略微夸大的各向异性热因子。然而，在 150 K 的 CuKα 结构中没有观察到这种效应，所有各向异性热因子包括烷基链中的热因子都被减少以覆盖更小的整体值范围。因此，可以得出结论，在 295 K 的烷基链中观察到的效应仅仅是一种热性质，而不是一种无序效应。不存在异常的键长或角度。联苯部分分别在 0.035 Å 和 0.020 Å 范围内是平面的。计算了所有环对的二面角。由对称中心相关的分子之间的分子间距离的计算揭示了许多范德华相互作用的存在。观察到氰基联苯化合物晶体结构的典型氢键基序。分子堆积方式对应于近晶相前体的堆积方式。图形摘要 7CBB (a) Mo RT 结构的烷基链热椭球与结构其余部分的那些相比明显夸大，这种效应在 (b) Cu LT 结构中不存在（用 Ortep/Raster 绘制（ Barnes in J Appl Cryst 30:568, 1997；Merritt and Bacon in Methods Enzymol 277:505–524, 1997))。