Synthesis, biological activity and assembly of pH-responsive alkyl-substituted naphthalene-type hydrazonotriazole organogelators

Hydrazones have been a significant group of materials with diverse pharmacological and industrial applications, such as treatment of cardiovascular diseases, parasitic infections, and viral disorders, as well as cosmetic and food additives. In this context, we present the synthesis and characterization of novel hydrazonotriazole analogues with different hydrophobic alkoxy units. The synthesized alkyl-substituted naphthalene-type hydrazonotriazoles were able to act as pH-sensitive and thermoreversible organogelators. They were prepared by a straightforward aldol condensation of 2-naphthalaldehyde with different adducts of 1-(5-methyl-1-(4-alkoxyphenyl)-1H-1,2,3-triazol-4-yl)ethan-1-one at room temperature in ethanolic solution and in the presence of sodium hydroxide as a catalytic agent. The provided compounds were exposed to condensation reaction with (2,4-dinitrophenyl)hydrazine in a refluxing acid ethanolic solution. Different spectroscopic methods were utilized to analyze and prove the chemical structures of the naphthalene-type hydrazonotriazoles, inclusing FT-IR, elemental analysis, and NMR spectra. The photophysical properties of the prepared hydrazonotriazoles were reported. The alkyl-substituted naphthalene-type hydrazonotriazole gelators were able to gelate a variety of solvents, displaying a sol–gel reversible response to pH changes together with colorimetric change from yellow to purple. The optimal gelation was monitored for nonyl-substituted hydrazone in a variety of solvents, demonstrating thermal stability up to 58 °C, and critical gelator concentration (CGC) of ∼ 1–11 mM. Several analytical methods were used to inspect the morphological properties of the hydrazonotriazole-based organogelators, displaying self-assembled nanofibers (7–15 nm). Both cytotoxic and antimicrobial activity of the alkyloxy-containing naphthalene-type hydrazonotriazole gelators was investigated.