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.