Thiacalix[4]‐bis‐crown with Hard Cavities and Soft Bridges Exhibiting Endocyclic Potassium(I) Complexes and Exocyclic Silver(I) Coordination Polymers

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

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 L², O₂S₂-thiacrown-ether L³, and O₂S₂-bridged thiacalixtube L⁴). 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 Hg²⁺ ions vs. other soft metal ions. In thioether L² and thiacalixtube L⁴, 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 Hg²⁺ species). Theoretical calculations for thioether L² 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 L² complexes and Hg-thiacalixtube L⁴ complex for the case of coordination around the metal center involving two alkyl sulfide groups (Hg²⁺) or sulfur atoms on the lower rim and bridging unit (Ag⁺). In thiacrown L³, 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. Hg²⁺ ion uptake by the Langmuir-Blodgett (LB) films of ligand L³ 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 Hg²⁺ ions, which could be useful in the development of Hg²⁺-selective water purification systems or thin-film sensor devices.

K-doped CeO2-ZrO2 for CO2 thermochemical catalytic splitting

Green syngas production is a sustainable energy-development goal. Thermochemical H2O/CO2 splitting is a very promising sustainable technology allowing the production of H2 and CO with only oxygen as the by-product. CeO2-ZrO2 systems are well known thermochemical splitting catalysts, since they combine stability at high temperature with rapid kinetics and redox cyclability. However, redox performances of these materials must be improved to allow their use in large scale plants. K-doped systems show good redox properties and repeatable performances. In this work, we studied the effect of potassium content on the performances of ceria-zirconia for CO2 splitting. A kinetic model was developed to get insight into the nature of the catalytic sites. Fitting results confirmed the hypothesis about the existence of two types of redox sites in the investigated catalytic systems and their role at different K contents. Moreover, the model was used to predict the influence of key parameters, such as the process conditions.

Metallosupramolecules of pillar[5]-bis-trithiacrown including a mercury(ii) iodide ion-triplet complex

A combination of pillar[5]-bis-trithiacrown (L) and mercury(ii) halides afforded a monomer complex (Cl^--form), a 1-D coordination polymer (Br^--form) and a supramolecular ion-triplet complex [(I·Hg·I)@L] (I^--form). In the ion-triplet complex, the host encapsulates the (I^--Hg²⁺-I^-) entity via Hg²⁺π and C-HI^- interactions, reflecting geometrical complementarity.

Influence of anions and mole ratio on the formation of 2-D coordination networks of thiacalix[4]-bis-monothiacrown-5

Anion and mole-ratio dependent formation of 2-D coordination polymers of thiacalix[4]-bis-monothiacrown-5 incorporating sulfur bridges in the rim and a sulfur donor in the crown loop is reported.

Multi-point interaction-based recognition of fluoride ions by tert-butyldihomooxacalix[4]arenes bearing phenolic hydroxyls and thiourea

A series of p-tert-butyldihomooxacalix[4]arenes bearing phenolic hydroxyls and thiourea moieties were prepared to investigate their anion binding behavior.