Characterization of At- species in simple and biological media by high performance anion exchange chromatography coupled to gamma detector.

Astatine is a rare radioelement belonging to the halogen group. Considering the trace amounts of astatine produced in cyclotrons, its chemistry cannot be evaluated by spectroscopic tools. Analytical tools, provided that they are coupled with a radioactive detection system, may be an alternative way to study its chemistry. In this research work, High Performance Anion Exchange Chromatography (HPAEC) coupled to a gamma detector (γ) was used to evaluate astatine species under reducing conditions. Also, to strengthen the reliability of the experiments, a quantitative analysis using a reactive transport model has been done. The results confirm the existence of one species bearing one negative charge in the pH range 27.5. With respect to the other halogens, its behavior indicates the existence of negative ion, astatide At-. The methodology was successfully applied to the speciation of the astatine in human serum. Under fixed experimental conditions (pH 7.47.5 and redox potential of 250 mV) astatine exists mainly as astatide At- and does not interact with the major serum components. Also, the method might be useful for the in vitro stability assessment of 211At-labelled molecules potentially applicable in nuclear medicine

Rapid and Efficient Removal of Perfluorooctanoic Acid from Water with Fluorine-Rich Calixarene-Based Porous Polymers

On account of its nonbiodegradable nature and persistence in the environment, perfluorooctanoic acid (PFOA) accumulates in water resources and poses serious environmental issues in many parts of the world. Here, we present the development of two fluorine-rich calix[4]arene-based porous polymers, FCX4-P and FCX4-BP, and demonstrate their utility for the efficient removal of PFOA from water. These materials featured Brunauer–Emmett–Teller (BET) surface areas of up to 450 m^{2} g^{-1}, which is slightly lower than their nonfluorinated counterparts (up to 596 m^{2} g^{-1}). FCX4-P removes PFOA at environmentally relevant concentrations with a high rate constant of 3.80 g mg^{-1} h^{-1} and reached an exceptional maximum PFOA uptake capacity of 188.7 mg g^{-1}. In addition, it could be regenerated by simple methanol wash and reused without a significant decrease in performance

Structures and properties of solvated and unsolvated isopropyl functionalised calix[4]arenes

The tetra-iso-propyl ethers of calix[4]arene and p-t-butylcalix[4]arene have been isolated in the cone conformation, and structurally characterized as chloroform solvates. Thermogravimetric analysis demonstrated that the parent iso-propylcalix[4]arene solvate is significantly more stable than the p-t-butylcalix[4]arene analogue, retaining the solvent up to a temperature of of 125 °C. It was found that the calix[4]arene ether sublimes at atmospheric pressure, and solvent-free crystals appropriate for structure determination were produced at reduced pressure. The p-t-butylcalix[4]arene ether was also isolated without solvent in the lattice, but in this case the calixarene was crystallized from acetone, as sublimation did not produce crystals of sufficient quality

Synthesis of macrocyclic receptors with intrinsic fluorescence featuring quinizarin moieties

An unprecedented class of macrocycles with intrinsic fluorescence consisting of phenolic trimers and quinizarin is developed. Though they are lacking strong hydrogen bonds as observed in calixarenes, the two examples introduced here each adopt a vase-like conformation with all four aromatic units pointing in one direction (syn orientation). This “cone” conformation has been confirmed by NMR spectroscopy, molecular modeling, and X-ray crystallography. The laminar, electron-rich fluorophore as part of the macrocycle allows additional contacts to enclosed guest molecules

Nucleophilic Functionalization of the Calix[6]arene Para- and Meta-Position via p‑Bromodienone Route

It is here demonstrated that the p-bromodienone route, previously reported for calix[4]arenes, is also effective for the functionalization of the calix[6]arene macrocycle. Thus, alcoholic O-nucleophiles can be introduced at the calix[6]arene exo rim. In addition, the reaction of a calix[6]arene p-bromodienone derivative with an actived aromatic substrate, such as resorcinol, led to the first example of a meta-functionalized, inherently chiral calix[6]arene derivativ