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

Abstract

Crystal engineering and supramolecular synthons approach are applied to synthesize a series of 2aminothiazole (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 (5methyl-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.

Formation of Salts and Molecular Ionic Cocrystals of Fluoroquinolones and α,ω-Dicarboxylic Acids

“…41 Yadav et al studied the gelator properties of 24 cocrystals of 2-aminothiazole with dicarboxylic acids. 42 One of the cocrystals was able to gel water, and this was attributed to the presence of hydrophilic cavities that immobilize water molecules. In addition to NH +...− OC(R)O ... HOOC (hydrophilic regions) structures, the crystal structure of (enro + )(sub − )•H 2 O shows unused Hbonding capacity around the fluoroquinolone that makes this class of organic salts good gel formers.…”

“…The creation of 1D motifs with hydrophilic regions is the classic requirement for the gelation of water . Yadav et al studied the gelator properties of 24 cocrystals of 2-aminothiazole with dicarboxylic acids . One of the cocrystals was able to gel water, and this was attributed to the presence of hydrophilic cavities that immobilize water molecules.…”

Diversity in Supramolecular Solid-State Architecture Formed by Self-Assembly of 1-(Diaminomethylene)thiourea and Aliphatic Dicarboxylic Acids

“…Aliphatic dicarboxylic acid functional groups are known to form robust intermolecular interactions with several organic N-bases forming different hydrogen bonding supramolecular complexes in solids. − Using 1-(diaminomethylene)­thiourea as an organic base for crystallization with aliphatic dicarboxylic acids depending on the deprotonation of one or both COOH groups yields base–acid supramolecular complexes with 1:1 or 2:1 ratio. In the studied supramolecular complexes 1 – 8 the interaction between the 1-(diaminomethylene)­thiouron-1-ium cation and oppositely charged singly or doubly deprotonated aliphatic dicarboxylate anions may be realized in different modes as shown in Scheme .…”