Novel dimeric cholesteryl-based A(LS)2 low-molecular-mass gelators with a benzene ring in the linker

Three novel dimeric cholesteryl-based A(LS)2 low-molecular-mass organic gelators (LMOGs) with phthaloyl, isophthaloyl, or terephthaloyl moieties in the linkers were designed and prepared. According to the linker structures, the compounds are denoted as 1 (o-), 2 (m-), and 3 (p-), respectively. Gelation tests revealed that the difference of relative positions of two cholesterol moieties in the benzene ring can produce a dramatic change in the gelation behaviors of the compounds. Importantly, 2 and 3 are more efficient gelators than 1, and their self-assembly behaviors are also very different from each other as revealed by scanning electron microscopy (SEM) measurements. Very interestingly, 2 gels xylene spontaneously at room temperature, and the sol–gel phase transition of the system is mechanically controllable. FTIR and 1H NMR spectroscopy studies revealed that hydrogen bonding and π–ππ–π interactions between the molecules of the gelators play an important role in the formation and maintenance of the gels. The X-ray diffraction (XRD) analysis revealed that in the gel of 2/benzene, 2 aggregated into a layered structure with an interlayer distance of 3.54 nm, which is just the length of 2.

Graphical abstractDifference of the relative positions of two cholesterol moieties in a benzene ring can produce a dramatic change in gelation behavior. More interestingly, a distinct thixotropic gel system was discovered.Figure optionsDownload full-size imageDownload as PowerPoint slide