Examples of a new type of cryptophane molecule incorporating aromatic groups in the bridges (1-4) and, for the first time, being also supplied with three endo-positional ionizable carboxylic acid functions (1) have been synthesized and characterized. The cryptophane triester 2 yielded a solvate (channel inclusion compound) with trichloromethane and water, the X-ray crystal structure of which is reported. The complexation of 1 with low-molecular-weight alcohols in solution was studied, and the liquid-liquid extraction of different metal ions including alkali (Na(+), Cs(+)), alkaline earth (Mg(2+), Ca(2+), Sr(2+), Ba(2+)), and the lanthanide metal ions Eu(3+) and Yb(3+) in an extraction system containing metal nitrate buffer/H(2)O/1/CHCl(3) was examined. Molecular modeling calculations of the cryptophanes 1 and 2, and of the Eu(3+) complex of 1 were carried out contributing to the discussion.

A low-temperature single-crystal X-ray structural determination of [CuCl(L 1 )]ClO 4 ؒH 2 O [where L 1 = meso-2, 12dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene] is reported. The coordination geometry of the complex cation approximates square pyramidal, with the chloro ligand occupying an apical position. The latter group is associated with an intermolecular hydrogen bonding network involving the uncoordinated water molecule and the perchlorate counter ion. Density functional theory (DFT) has been applied to modeling the structure of this complex, both in the presence and the absence of the intermolecular hydrogen-bonding network. In the absence of this network a good fit to the X-ray structural parameters was obtained except for the Cu-Cl bond length. For this bond the calculated value (2.346 Å) was significantly shorter than the X-ray value [2.541( 2) Å] but, on incorporation of the hydrogen-bonded network, while the major portion of the computed structure remained almost identical to that obtained from the initial calculation, the Cu-Cl bond was now found to be longer at 2.572 Å, approximating the X-ray value quite closely. The study has been extended to similar/related systems for which structural data are available, confirming the wider applicability of this approach in modeling arrays of this type.

Structure-function relationships underlying the interaction of progressively N-benzylated N(4)O(2)-donor macrocycles with cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) have been probed using a range of techniques that include X-ray diffraction, DFT computations, solvent extraction, potentiometric stability constant determinations and competitive membrane transport experiments. Collectively, the results indicate that N-benzylation of the secondary amine donor groups of the parent macrocyclic ring results in an enhanced tendency towards selectivity for silver(I) relative to the other six metals investigated. The observed behaviour serves as additional exemplification of the previously proposed concept of selective 'detuning' as a mechanism for metal ion discrimination.

Solvent extraction as a well-established process in hydrometallurgy, waste treatment, and material preparation requires selective and effective complexing agents with high lipophilicity. The extractant types used in industry reach from simple acids, ethers, and esters to more complex chelating agents. Nowadays the progress of supramolecular chemistry offers interesting possibilities to control the selectivity of metal extraction and to achieve a tailored ligand. In this paper, solvent extraction studies are presented for transition-metal ions with position isomers of alkylated 8-hydroxyquinolines from the chelating type as well as for amino and imino cage compounds and their acyclic counterparts from the supramolecular type. In all cases the extraction selectivity and efficiency strongly depend both on the extractant architecture and on the aqueous-phase composition. It is clearly shown that manipulation of the chemistry in the investigated systems leads to significant changes of the graduated extractabilities.