Synthesis, Physicochemical Characteristics, Self-Assembly and Encapsulation Ability of per-Ethylene-Glycol-Functionalized Resorcin[4]Arenes and Their Molecular Capsules: On the Road to Liquid Capsules.

内容摘要

Self-assembled molecular cages and capsules attracted considerable attention, owing to their unique structures and ability to function as nano-reactors and catalysts. In recent years, porous liquids have emerged into an intriguing class of functional materials. Herein, we prepared a series of per-ethylene-glycol (EG)-functionalized resorcin[4]arene hosts, bearing side chains with three, four, or five EG units (compounds 1d, 1e, and 1f, respectively). We studied their melting points, solubility, self-assembly, and encapsulation abilities. Interestingly, 1e and 1f were found to be viscous liquids at RT and compound 1d melts at 104°C-105°C, while alkyl-substituted resorcin[4]arenes (1a and 1c) melt at ∼300°C. We found in contrast to expectations, that the number of EG groups on the side chains affects the self-assembly, the stability of the formed aggregates, and the encapsulation power of those systems in organic solvents. System 1d behaved, in CDCl3, much like alkyl-substituted resorcin[4]arenes, forming self-assembled hexameric capsules of comparable stability and size capable of encapsulating even tetra-hexyl ammonium salts. Compounds 1e and 1f, however, form, in CDCl3, hexameric capsules, which are more dynamic than the capsules of 1c or even 1d that encapsulate smaller ammonium salts and appear to be promising candidates for the preparation of liquid capsules and capsular liquids.