Thiacalixarenes with Sulfur Functionalities at Lower Rim: Heavy Metal Ion Binding in Solution and 2D-Confined Space

• Published in: International journal of molecular sciences Vol. 23; no. 4; p. 2341
• Main Authors: Muravev, Anton, Yakupov, Ayrat, Gerasimova, Tatiana, Islamov, Daut, Lazarenko, Vladimir, Shokurov, Alexander, Ovsyannikov, Alexander, Dorovatovskii, Pavel, Zubavichus, Yan, Naumkin, Alexander, Selektor, Sofiya, Solovieva, Svetlana, Antipin, Igor
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 20.02.2022; MDPI
• Subjects: Ag+ and Hg2+ complexes; Aggregates; Aqueous solutions; Band theory; Binding; Blue shift; Calixarenes; Charge transfer; Confined Spaces; Deionization; Heavy metals; Ions; Langmuir monolayers; Langmuir-Blodgett films; Ligands; Liquid phases; Mercury - chemistry; Metal ions; Metals - chemistry; Monolayers; Monomolecular films; NMR; NMR spectroscopy; Nuclear magnetic resonance; Photoelectron spectroscopy; Photoelectrons; Salts; Selectivity; Silver; Single crystals; Sulfides; Sulfides - chemistry; Sulfur; thiacalixarenes; thiacrown-ethers; Thioethers; Topology; Water - chemistry; Water purification; X ray photoelectron spectroscopy; Ag+ and Hg2+ complexes; thiacalixarenes; Langmuir monolayers; X-ray photoelectron spectroscopy; thiacrown-ethers
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms23042341

Sulfur-containing groups preorganized on macrocyclic scaffolds are well suited for liquid-phase complexation of soft metal ions; however, their binding potential was not extensively studied at the air-water interface, and the effect of thioether topology on metal ion binding mechanisms under various conditions was not considered. Herein, we report the interface receptor characteristics of topologically varied thiacalixarene thioethers (linear bis-(methylthio)ethoxy derivative , O S -thiacrown-ether , and O S -bridged thiacalixtube ). The study was conducted in bulk liquid phase and Langmuir monolayers. For all compounds, the highest liquid-phase extraction selectivity was revealed for Ag and Hg ions vs. other soft metal ions. In thioether and thiacalixtube , metal ion binding was evidenced by a blue shift of the band at 303 nm (for Ag species) and the appearance of ligand-to-metal charge transfer bands at 330-340 nm (for Hg species). Theoretical calculations for thioether and its Ag and Hg complexes are consistent with experimental data of UV/Vis, nuclear magnetic resonance (NMR) spectroscopy, and single-crystal X-ray diffractometry of Ag-thioether complexes and Hg-thiacalixtube complex for the case of coordination around the metal center involving two alkyl sulfide groups (Hg ) or sulfur atoms on the lower rim and bridging unit (Ag ). In thiacrown , Ag and Hg binding by alkyl sulfide groups was suggested from changes in NMR spectra upon the addition of corresponding salts. In spite of the low ability of the thioethers to form stable Langmuir monolayers on deionized water, one might argue that the monolayers significantly expand in the presence of Hg salts in the water subphase. Hg ion uptake by the Langmuir-Blodgett (LB) films of ligand was proved by X-ray photoelectron spectroscopy (XPS). Together, these results demonstrate the potential of sulfide groups on the calixarene platform as receptor unit towards Hg ions, which could be useful in the development of Hg -selective water purification systems or thin-film sensor devices.