Thermodynamics of Anion Binding by (Thio)ureido-calix[4]arene Derivatives in Acetonitrile.

In this work, we developed (thio)ureido-calix[4]arene derivatives and thoroughly explored their anion-binding properties in acetonitrile. A series of anions, including important inorganic ones (Cl, HSO , HPO , and HPO ) and several ever-present carboxylates (acetate, benzoate, and fumarate), were studied. All systems were investigated by several methods (NMR, ITC, and UV) used in a synergistic fashion, providing their comprehensive thermodynamic description.

Anion-Binding Properties of Short Linear Homopeptides.

A comprehensive thermodynamic and structural study of the complexation affinities of tetra (), penta (), and hexaphenylalanine () linear peptides towards several inorganic anions in acetonitrile (MeCN) and ,-dimethylformamide (DMF) was carried out. The influence of the chain length on the complexation thermodynamics and structural changes upon anion binding are particularly addressed here. The complexation processes were characterized by means of spectrofluorimetric, H NMR, microcalorimetric, and circular dichroism spectroscopy titrations.

Supramolecular Handshakes: Characterization of Urea-Carboxylate Interactions Within Calixarene Frameworks.

The research of molecular capsules offers high application potential and numerous benefits in various fields. With the aim of forming supramolecular capsules which can be reversibly assembled and dissociated by simple external stimuli, we studied interactions between calixarenes containing urea and carboxylate moieties. To this end two ureido-derivatives of p-tert-butylcalix[4]arene comprising phenylureido-moieties and diacetate-calix[4]arenes were prepared.

Enhancing the Cation-Binding Ability of Fluorescent Calixarene Derivatives: Structural, Thermodynamic, and Computational Studies.

Novel fluorescent calix[4]arene derivatives and were synthesized by introducing phenanthridine moieties at the lower calixarene rim, whereby phenanthridine groups served as fluorescent probes and for cation coordination. To enhance the cation-binding ability of the ligands, besides phenanthridines, tertiary-amide or ester functionalities were also introduced in the cation-binding site. Complexation of the prepared compounds with alkali metal cations in acetonitrile (MeCN), methanol (MeOH), ethanol (EtOH), -dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) was investigated at 25 °C experimentally (UV spectrophotometry, fluorimetry, microcalorimetry, and in the solid state by X-ray crystallography) and by means of computational techniques (classical molecular dynamics and DFT calculations).

Utilization of a kinetic isotope effect to decrease decomposition of ceftriaxone in a mixture of DO/HO.

The discovery of cephalosporin and demonstration of its improved stability in aqueous solution, as well as enhanced in vitro activity against penicillin-resistant organisms, were major breakthroughs in the development of β-lactam antibiotics. Although cephalosporins are more stable with respect to hydrolytic degradation than penicillins, they still experience a variety of chemical transformations. The present study offers an insight into the rates and mechanisms of ceftriaxone degradation at the therapeutic concentration in water, a mixture of water and deuterium oxide, and deuterium oxide itself at the neutral pH.