Disulfo-NOPON—A new chelator for complexometric analysis and liquid-liquid extraction of stable isotopes and radionuclides of metal ions

Abstract

The synthesis, chemical structure and physico-chimical properties of a new heterocyclic ligand, disulfo-NOPON (2,6-bis(5-(5-sulfonaphthalen-1-yl)oxazol-2-yl)pyridine), as well as its complexation ability, spectral and inter-phase partition properties of its complexes with metal ions, are described. Given potential applications of disulfo-NOPON in the liquid-liquid extraction and complexometric determination of ecotoxic and radioactive contaminants, studies were conducted on complex formation with stable and radioactive isotopes of Sr2+, Y3+, Ce4+, and UO22+ ions. Theoretical studies on complexes' structures have revealed that the formation of three isomeric complexes is possible, depending on the ligand's conformation. Furthermore, it has been found that under ``green'' extraction conditions, disulfo-NOPON forms different isomers of complexes in the organic and aqueous phases. Specifically, in the organic phase, disulfo-NOPON binds to a metal ion through the nitrogen atoms of its oxazole fragments, while in the aqueous phase, complex formation involves the participation of the oxygen atoms within the oxazole moieties. The results indicate a strong correlation between theoretical results and experimental values of spectral parameters, stability constants, and inter-phase distribution coefficients of complexes. Based on this preliminary analysis, it is evident that disulfo-NOPON holds promise for the spectrophotometric and spectrofluorimetric analysis of uranyl ions in both aqueous and organic media. Additionally, it can be employed for the extraction-based accumulation of cerium ions, facilitating their subsequent quantitative analysis.