There are few examples of single-crystal structure determinations of gelators, as gel formation requires that the dissolved gelator self-assemble into a three-dimensional network structure incorporating solvent via noncovalent interactions rather than self-assembly followed by crystallization. In the solid-state structures of the isostructural compounds 4,4′-bis[5-(methoxycarbonyl)pentyloxy]biphenyl (BBO6-Me), C26H34O6, and 4,4′-bis[5-(ethoxycarbonyl)pentyloxy]biphenyl (BBO6-Et), C28H38O6, the molecules sit on a crystallographically imposed center of symmetry, resulting in strictly coplanar phenyl rings. BBO6-Me behaves as an organogelator in various alcohol solvents, whereas BBO6-Et does not. The extended structure reveals bundles of molecules that form a columnar superstructure. Framework-energy calculations reveal much stronger interaction energies within the columns (−52 to −78 kJ mol−1) than between columns (−2 to −16 kJ mol−1). The intracolumnar interactions are dominated by a dispersion component, whereas the intercolumnar interactions have a substantial electrostatic component.
凝胶体的单晶结构测定实例很少,因为凝胶体的形成需要溶解的凝胶体通过非共价相互作用自组装成一个包含溶剂的三维网络结构,而不是先自组装再结晶。在等结构化合物 4,4′-双[5-(甲氧基羰基)戊氧基]联苯(BBO6-Me)(C26H34O6)和 4,4′-双[5-(乙氧基羰基)戊氧基]联苯(BBO6-Et)(C28H38O6)的固态结构中,分子位于晶体学上强加的对称中心,形成严格共面的苯基环。BBO6-Me 在各种醇类溶剂中表现为有机凝胶剂,而 BBO6-Et 则不然。扩展结构揭示了形成柱状上层结构的分子束。框架能计算显示,柱内的相互作用能(-52 至 -78 kJ mol-1)比柱间的相互作用能(-2 至 -16 kJ mol-1)强得多。柱内相互作用由分散成分主导,而柱间相互作用则有很大的静电成分。