Combinatorial Library Approach to Realize 2‑Aminothiazole-Based Two-Component Hydrogelator: A Structure–Property Correlation

Crystal engineering and supramolecular synthons approach are applied to synthesize a series of 2-aminothiazole (and its methyl derivatives) salts/cocrystals with various dicarboxylic acids. On the basis of combinatorial library approach, 24 new salts/cocrystals of 2-aminothiazole and its methyl derivatives with various dicarboxylic acid (aliphatic unsaturated and saturated backbone) were synthesized and characterized. All the synthesized salts were subjected to gelation test in various solvents (polar and nonpolar). Interestingly, one of the salts/cocrystals, i.e., B3A6 (5-methyl-2-aminothiazolium hydrogen decandioate) was found to be capable of immobilizing water at slightly higher minimum gelator concentration (MGC). A structure–property correlation between various cocrystals/salts based on single crystal X-structure of 11 compounds was undertaken. The gelation property of 2-aminothiazole-based gelling agent was found to be governed by the position of a methyl group on the thiazole ring, a length of the aliphatic carbon chain of dicarboxylic acid, and formation of hydrogen bonded network (HBN) leading to void in the single crystal structure. The comparison of single crystal X-ray structures of nongelators and a gelator were undertaken to understand the probable mechanism of hydrogelation in the series of 2-aminothiazole-based salts/cocrystals.