Metal ion complexation in acetonitrile by cone,di-ionised calix[4]arene-1,2-crown ethers with two pendant dansyl fluorophores

Four cone calix[4]arene-1,2-crown ethers each with two ionisable side arms containing dansyl groups are synthesised. The crown ether ring on the lower rim is varied from crown-4 to crown-5 with hydrogen or tert-butyl groups on the para position of the upper rim. Di(tetramethylammonium) salts of the di-ionised ligands are utilised for spectrofluorimetric titration experiments in MeCN. The influence of alkali metal, alkaline earth metal and selected transition and heavy metal (Co²⁺, Fe²⁺, Hg²⁺, Mn²⁺, Pb²⁺, Zn²⁺ and Fe³⁺) cations on the spectroscopic properties of the two dansyl groups linked to the lower rim of the conformationally locked, di-ionised calix[4]arene-1,2-crown ether frameworks is investigated by emission spectrophotometry. All of the metal cations induce red shifts in the emission spectra of the di-ionised ligands. The metal cations produce enhancement or quenching of the fluorescence emissions. Changes in the fluorescence emission as a function of the metal cation identity, the lower rim crown ether ring size and the absence or presence of upper rim tert-butyl groups are investigated.     

Multi-residue enantiomeric analysis of pharmaceuticals and their active metabolites in the Guadalquivir River basin (South Spain) by chiral liquid chromatography coupled with tandem mass spectrometry

This paper describes the development and application of a multi-residue chiral liquid chromatography coupled with tandem mass spectrometry method for simultaneous enantiomeric profiling of 18 chiral pharmaceuticals and their active metabolites (belonging to several therapeutic classes including analgesics, psychiatric drugs, antibiotics, cardiovascular drugs and β-agonists) in surface water and wastewater. To the authors’ knowledge, this is the first time an enantiomeric method including such a high number of pharmaceuticals and their metabolites has been reported. Some of the pharmaceuticals have never been studied before in environmental matrices. Among them are timolol, betaxolol, carazolol and clenbuterol. A monitoring programme of the Guadalquivir River basin (South Spain), including 24 sampling sites and five wastewater treatment plants along the basin, revealed that enantiomeric composition of studied pharmaceuticals is dependent on compound and sampling site. Several compounds such as ibuprofen, atenolol, sotalol and metoprolol were frequently found as racemic mixtures. On the other hand, fluoxetine, propranolol and albuterol were found to be enriched with one enantiomer. Such an outcome might be of significant environmental relevance as two enantiomers of the same chiral compound might reveal different ecotoxicity. For example, propranolol was enriched with S(?)-enantiomer, which is known to be more toxic to Pimephales promelas than R(+)-propranolol. Fluoxetine was found to be enriched with S(+)-enantiomer, which is more toxic to P. promelas than R(?)-fluoxetine.     

Nucleophilic Substitution on 5-Nitrobenzofurazan-3-Oxide: A New Synthetic Route for Novel Benzofurazan-5, 5′-Oxybis 3, 3′-Dioxide and Benzofurazan-5, 5′-Thiobis-3, 3′-Dioxide

The nucleophilic substitution of the nitro group in 5-nitrobenzofurazan-3-oxide is studied undder soild-liquid phase-transfer catalysis (PTC) conditions.     

Drop Size Distribution Bimodality and Its Effect on O/W Emulsion Viscosity

The research work on why and how distribution bimodality tends to reduce the viscosity of a particulate suspension is reviewed. The transfer of the corresponding concepts to emulsions requires some statistical tools, and becomes particularly easy with probability scale plotting which is reviewed. Viscosity reduction can be attained for different kinds of fine and coarse emulsion associations. The results are shown to depend on the characteristics of the base emulsions as well as on the way they are mixed.     

Design,synthesis, and characterization of fullerene–peptide–steroid covalent hybrids

The present study reports the synthesis, spectral characterization, self-assembly properties, and preliminary in vitro study of antioxidant capacity of two triple covalent hybrids consisting of fullerene C₆₀, peptide, and steroidal moiety. Previously synthesized fulleropyrrolidinic acid and pregnenolone were connected by peptide linker using a multistep DCC/DMAP and/or EDC/HOBT esterification/amidation procedure. The hybrids were characterized by comparative analysis of spectroscopic data obtained from FTIR, UV–vis, HRMS, and extensive NMR experiments (¹H, ¹³C, COSY, HSQC, and HMBC). The self-assembling properties and morphology of triads samples prepared by drop-drying method were examined by scanning electron microscopy (SEM). Preliminary in vitro antioxidant activity was studied by Ferrous ion Oxidation-Xylenol orange (FOX) method.