Effect of\nAnion-Directed Structural Tuning of Triazole-Containing\nAg(I) Coordination Polymers for “Turn-on” Sensing of\nthe Disulfide (−S–S−) Amino Acid over the Monosulfide\n(−SH) Form: Experiments and DFT Corroboration

Identification\nof disulfide-peptide-bond-containing glutathione\n(GSSG) over the monosulfide form (GSH) remains a very challenging\ntask because of their identical chemical properties. Although GSH\ndetection has been well documented, selective detection of GSSG has\nrarely been reported. Here, four cationic Ag-based coordination polymers\n(Ag CPs) were synthesized using newly synthesized monotriazole linker\n3-amino-5-(4<i>H</i>-1,2,4-triazol-4-yl)pyridine to selectively\nscreen GSSG over GSH. The judicious choice of the counteranion in\nthe metal salt changes the architecture, which affects the detection\nlimit at the parts per million level. The restriction of the photoinduced\nelectron transfer process is the driving reason for the enhancement\nof the fluorescence, owing to the favorable energy band gap match\nof the Ag CPs with GSSG over GSH. The de novo strategy for incorporating\npolar heteroatoms (N) into the CP network plays a pivotal role in\nthe host–guest noncovalent interactions with donor–acceptor\ntransfer of electrons, which was supported by X-ray photoelectron\nspectroscopy and density functional theory studies. The Ag CPs are\nthermochemically robust, recyclable, and work efficiently in a very\nshort time (within ∼14–18 s) in different pH ranges.\nAdditionally, detection of GSSG in serum samples was carried out with\nappreciable detection limits and recovery percentages (94.40–117.89%).