The first calixarene-based fluorogenic Hg(II)-selective extractant, 5,11,17,23-tetrakis(1,1-dimethylethyl)-25,27-bis(N-(5-dimethylaminonaphthalene-1-sulfonyl)carbamoylmethoxy)-26,28-dimethoxycalix[4]arene (2), is reported. In solvent extraction from aqueous acidic solutions (HNO(3)), 2 exhibits excellent selectivity for Hg(II) over a wide range of transition, alkali, and alkaline earth metal cations. Quenching of its fluorescence due to Hg(II) coordination is unaffected by the presence of 100-fold excesses of alkali metal cations, alkaline earth metal cations, Ag(I), Tl(I), Cd(II), Co(II), Cu(II), Ni(II), Pb(II), Pd(II), Zn(II), or Fe(III).

As evaluated with 15 crown ethers which contain varying numbers of benzo substituents, the magnitude of the extraction selectivities (and in one case, the selectivity order) of aromatic group-containing ionophores for alkali metal picrates may vary significantly from those for alkali metal salts with inorganic anions as a result of π−π interactions between picrate ion and an aromatic unit of the ionophore. The importance of the “picrate effect” increases as the number of benzo groups in the crown ether is enhanced and varies with their location in the macrocycle. To verify the involvement of picrate−crown ether π-stacking in complexation, crown ether−alkali metal picrate complexes were examined in solution by 1H NMR spectroscopy and solid-state structures for nine complexes were determined by X-ray diffraction. Dependence of the chemical shift for the picrate proton singlet in the NMR spectrum on the metal cation and/or macrocycle identity in the metal picrate−crown ether complex was found to be a convenient tool for studying anion−ligand π−π interactions in solution.

Separation factor values for pairs of alkali metal cations determined in competitive solvent extractions of alkali metal picrates from aqueous solutions into chloroform by a variety of benzo- and cyclohexano-group-containing crown ethers vary significantly from extrapolations based upon the results of single-species extraction experiments. For almost all of the crown ether-alkali metal cation combinations examined, the separation factor values are greater for competitive solvent extraction. In view of the unexpected results for sodium picrate extraction by dibenzo-24-crown-8, the solid-state structure of the isolated complex was determined.

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Lariat Ether Carboxylic Acids, O-Benzylhydroxamates and Hydroxamic Acids with Fluorinated Substituents: Synthesis, Metal Ion Complexation and Solubility in Supercritical Carbon Dioxide. -Title fluorine-containing crown ethers such as (I) and (II) are compared with non-fluorinated analogues with respect to increasing the solubility in supercritical CO 2 to affect extraction of lanthanide ions from aqueous solutions into CHCl 3 and to their response toward alkali metal cations in solvent polymeric membrane electrodes. -(ELSHANI, SADIK; DU, HONGSHAN; LAINTZ, KENNETH E.; NATALE, NICHOLAS R.; WAI, CHIEN M.; ELKARIM, NAZAR S. A.; BARTSCH, RICHARD A.; Tetrahedron 56 (2000) 27, 4651-4657; Dep. Chem. Biochem., Tex. Tech. Univ., Lubbock, TX 79409, USA; EN)