Synthesis and gelation behaviors of five new dimeric cholesteryl derivatives

Abstract

Five new diacid amides of di-cholesteryl l-glycinates were designed and prepared. The compounds with linkers containing 0, 1, 2, 3, or 4 methylene units are denoted as 1, 2, 3, 4, and 5, respectively. Their gelation behaviors in 25 solvents were tested as novel low-molecular-mass organic gelators (LMOGs). It was shown that the length of the linker connecting the two-cholesteryl residues in a gelator plays a crucial role in the gelation behavior of the compound. 1 gels 11 of the 25 solvents tested at a concentration lower than 1.0%, while 2 gels 17 of the solvents tested. 4 and 5, however, gel only 2 and 4 of them, respectively. SEM observation reveals that the lengths of the linkers and the identity of the solvents are the main factors affecting the structures of the aggregates in the gels. Experimentally, a clear linker effect on the microstructures of the gels was observed. As example, the aggregates of 1, 2 and 3 in benzene or 1-heptanol adopt structures of thin fibers, rods or lamellas, respectively. Furthermore, it was found that the gelation and aggregation behaviors of 2, 3, 4, and 5 in DMSO showed an even-odd effect.