Real Chemical States of the 3‑Sulfur Derivative of 1,2,4-Triazole in Different Conditions: Complex Experimental and Theoretical Studies

Triazole compounds have a wide range of applications in the biomedical field, and their adlayers on metal surfaces are used as anticorrosion agents and to build nanosensors and nanocatalysts. The knowledge of the chemical state of triazole derivatives and the structure of adlayers in different conditions is necessary for controlling the properties of applied systems. In this work, using different methods, chemical states of 3-sulfur derivatives of 1,2,4-triazole (TS) in different conditions have been established. The structure of this compound in the solid state was studied by X-ray diffraction, IR and Raman spectroscopy, and DFT calculations that indicated dimerization of the TS molecules resulting in the formation of 3,3′-disulfide-1,2-di­(1H-1,2,4-triazol-3-yl)­disulfane. The chemical states of TS in solutions at varying pH were determined with the help of Raman spectroscopy supported by H/D isotopic exchange experiments and DFT calculations. These results were useful in establishing also the chemical states of the TS molecules adsorbed at the nanostructured Ag surface in different conditions of pH and concentration of the surrounding solution, adsorption time, and electric potential applied to the Ag surface, which were examined by the SERS and XPS spectroscopy and DFT calculations of model complexes with silver cations. We demonstrated also a mutual influence of experimental conditions on the adlayer structure and the possibility of reversible switching between different chemical forms of the adsorbed molecules and different structures of the adlayers, which foreshadows their application as a tunable device.