The synthesis, complexation properties and catalytic activities under phase-transfer (PT) conditions of differently substituted cyclohexapeptoids are reported. Association constants, for small cationic alkali, and catalytic performances, in a model nucleophilic substitution, are comparable to those of representative crown ethers. Noteworthy, the N-[2-(2-methoxyethoxy)ethyl] side chain derivativ...

The feasibility of fabricating copper-sensitive chemically modified electrodes (CMEs) for trace analysis in aqueous and in 40% (v/v) ethanol-water media was investigated. Carbon paste electrodes modified with crown ethers were constructed by mixing the crown ethers into a graphite powder-paraffin oil matrix. The electrodes so formed were able to bind Cu(II) ions chemically and gave better volta...

the interaction between benzo-15-crown-5 (b15c5), dibenzo-18-crown-6 (db18c6), dibenzyl-daza-18crown-6 (dbzda18c6), n-phenyl-aza-15-crown-5 (npha15c5) and dibenzopyridine-18-crown-6 (dbpy18c6) with π-acceptor 2,3-dichloro-5,6-dicyanobenzoquinone (ddq) in chloroform solution was studied spectrophotometrically. the interaction of b15c5-ddq and db18c6-ddq caused the formation of 1:1 charge transfe...

The complexation reactions between Tl+ and Pb2+ ions and crown ethers 12-crown-4(12C4), 15-crown-5 (15C5), benzo-15-crown-5 (B15C5), 18-crown-6 (18C6), dicyclohexyl-18-crown-6 (DC18C6) and aza-18-crown-6 (A18C6) were studied in 90% acetonitrile and 90% ethanol solutions at 25 °C, using an a.c. polarographic technique. The stoichiometry and stability of the complexes we...

crown ethers 12-crown-4 (12c4), benzo-15-crown-5 (b15c5), 18-crown-6 (18c6), nitrobenzo-18-crown-6 (nb18c6) dibenzo-18-crown-6 (db18c6) and dicyclohexyl-18-crown-6 (dc18c6), dissolved in dichloromethane, are able to form oxonium-ion complexes in contact with aqueous sulfuric and hydrochloric acid solutions. this ability allows the transfer of cr(vi) oxanions from the acid media, through an orga...

Supercritical fluid CO 2 is an alternative solvent for extraction of metals. The solubility parameter of supercritical CO 2 varies with density resembling that of liquid hexane at moderate pressures in the supercritical region to those of chlorinated solvents at very high pressures. By changing density of supercritical CO 2 , the solvation environment of a metal chelate system can vary continuo...

Novel 4-acyl-5-pyrazolones having aza-15-crown-5 (HPMP-A15C5) and aza-18-crown-6 (HPMP-A18C6) moieties as an intramolecular synergist have been synthesized by simple coupling reactions between 1-phenyl-3-methyl-4-chloroacetyl-5-pyrazolone and the corresponding azacrown ethers. The solvent extraction of the divalent metal ions (Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+)) were exam...

Making one out of two: Dimeric boraza-crown ethers bridge the gap between metallacrowns and aza-crown with a strikingly simple synthesis. Dioxazaborocanes react alkoxides to form corresponding anionic boronates, which combine dimers upon ring-opening reactions. The presence was proven in solid state solution by X-ray crystallography NMR spectroscopy, respectively. influence counterion on stabil...