Supramolecular Walls from Cyclic Peptides: Modulating Nature and Strength of Weak Interactions

Both macrolactams cyclo-[NH−CH2−CC−CH2−C(Me)2-CO]n (n = 3 and n = 2) have been synthesized and crystallized. They have respectively one intramolecular hydrogen bond and no such bond. Both macrocycles self-assemble as parallel supramolecular walls with or without inclusion of solvent between them. The units of the former (n = 3) are held together by NH···π/NH···OC interactions, whereas they are glued by a very dense network of classical parallel-oriented hydrogen bonds, involving all the amides of the rings, in the latter (n = 2). In that case, the bulky C(Me)2 groups are located on the surface of the walls and can be held responsible for the piling process of the layers, by means of attractive van der Waals interactions. This spatial arrangement recalls the 3D structure of cellulose, where all constitutive sheets stack mostly via van der Waals forces.

已合成并结晶了两种大环内酰胺（macrolactams）：cyclo-[NH−CH2−C≡C−CH2−C(Me)2-CO]n（n=3与n=2）。二者各自带有一条分子内氢键，而另一种则无此类氢键。两种大环均自组装为平行超分子壁，壁间可包含或不包含溶剂分子。对于n=3的产物，其结构单元通过NH···π/NH···OC相互作用结合；而n=2的产物则通过致密的经典平行取向氢键网络实现黏合，该网络涵盖环上所有酰胺基团。在此体系中，庞大的C(Me)2基团位于超分子壁表面，可通过范德华吸引力驱动层状结构的堆叠过程。这种空间排布与纤维素的三维结构类似，其组成片层主要通过范德华力实现堆叠。