Odd–even effect in a thiazole based organogelator: understanding the interplay of non-covalent interactions on property and applications

Abstract

New series of thiazole based amides, namely, 1e [N-(thiazol-2-yl)pentadecamide] to 1h [N-(thiazol-2-yl)stearamide], 2e [N-(4-methylthiazol-yl)pentadecamide] to 2h [N-(4-methylthiazol-yl)stearamide], 3e [N-(5-methylthiazol-yl)pentadecamide] to 3h [N-(5-methylthiazol-yl)stearamide] were synthesized, characterized and investigated for their gelation properties. Interestingly, out of three series of thiazole amides synthesized, two (1e–1h and 3e–3h) had displayed odd–even effect on gelation property with an increase in the methylene functional group of alkyl chain attached with thiazole moiety. The gelation–non-gelation of solvents was found to be more significant for the series of compounds 1e–1h, whereas a subtle effect was observed in the series of compounds 3e–3h. A single crystal study of non-gelator (2d) highlighted the crucial role of the methyl group and its position on the thiazole moiety in bringing about a change in supramolecular synthon from a robust cyclic N–H⋯N interaction to the combination of N–H⋯N and N–H⋯O interactions. Self-assembly of four molecules of 2d led to the formation of a zero-dimensional (0-D) hydrogen bonded network instead of a one-dimensional hydrogen bonded network observed in gelling compounds mediated by (methyl)C–H⋯N, C–H⋯O and van der Waals interaction. Various gelling agents (3e–3h) were used for the synthesis of nearly spherical silver and ZnO nanoparticles using a sol–gel method, through encapsulation and stabilization of nanoparticles in the gel network. Interestingly, the alkyl chain lengths of thiazole amides were found to affect the size of synthesized Ag and ZnO nanoparticles.