Dosimetric Chromogenic Probe for Selective Detection of Sulfide via Sol-Gel Methodology.

Dinitrobenzenesulfonyl-protected naphthyl azo pyridine conjugate has been designed and synthesized. Compound acts as a nongelator in dimethyl sulfoxide (DMSO)-HO (1:1, v/v) while its hydroxy counterpart can form a nice gel in the same solvent. In the presence of sulfide, compound undergoes rapid sulfonate ester hydrolysis and results in the formation of azo-naphthol that responds in instant gelation. Such deprotection was extremely selective to sulfide; other analytes did not show measurable response. The sensing mechanism has been established by various spectroscopic techniques. Compound in solution (DMSO-HO) also shows a selective response toward sulfide over a series of other anions with a color change. Preparation of test kit with compound allows detection of sulfide in solution and vapor states. Such kind of dosimetric sensing of chemical analytes by improvising the protection/deprotection of functional groups in gelator structure is rare in the literature, and to the best of our knowledge, this is the first example of a stimuli-responsive low-molecular-weight gelator which dosimetrically senses sulfide over other nucleophilic substrates.