Jerald S. Bradshaw

Macrocycle-Facilitated Transport of Ions in Liquid Membrane Systems

Abstract Ion transport in various liquid membrane systems is discussed in terms of those factors which create the environment for efficient and selective transport. The following parameters which affect ion transport are discussed: membrane configuration, cation-macrocycle complex stability, macrocycle partitioning between membrane and water phases, proton ionization of acidic macrocycles, macrocycle concentration, anion type, ion concentration, membrane solvent type and receiving phase composition. A summary of existing models of ion transport is given along with possible applications to macrocycle-facilitated liquid membraneion transport.

Characterization of 5-chloro-8-methoxyquinoline appended diaza-18-crown-6 as a chemosensor for cadmium

Abstract 5-Chloro-8-methoxyquinoline appended diaza-18-crown-6 ( 1 ) selectively responds to Cd 2+ over other tested metal ions via a large increase in fluorescence. In addition, 1 selectively binds Cd 2+ over Zn 2+ . Compound 1 may be useful in measuring Cd 2+ concentrations in waste effluent streams and in food products.

A fluorescent sensor for magnesium ions

Diaza-18-crown-6 appended with two 5-chloro-8-hydroxyquinoline groups can serve as an effective chemosensor for Mg2+. The modified macrocycle will fluoresce in the presence of Mg2+ but not with other alkaline earth ions at pH 7.2. Mg2+ concentrations can be measured in the presence of Na2+, K+, Ca2+, Sr2+ and Ba2+.

Factors influencing enantiomeric recognition of primary alkylammonium salts by pyridino-18-crown-6 type ligands

Equilibrium constant (K), enthalpy change (ΔH), and entropy change (ΔS) values were determined for the interactions of a series of chiral pyridino-18-crown-6 type ligands with enantiomers of several primary alkylammonium salts in various solvents. Good enantiomeric recognition in terms of Δ logK was observed in many systems with Δ logK values greater than 0.4. The extent of enantiomeric recognition and the stabilities of the chiral crown ether-ammonium salt complexes were found to depend on the rigidity of the macrocyclic frame of the ligand, the type and arrangement of the donor atoms on the ligand, the bulkiness of the substituents on the ligands chiral centers, the location of the chiral centers on the ligand, and the solvent. The effects of these factors on the extent of enantiomeric recognition and on the stabilities of the complexes were examined for the systems studied.

Accomplishment of difficult chemical separations using solid phase extraction

A solid phase extraction (SPE) system is described which is capable of highly selective removal of trace amounts of metal ions from solutions containing matrices which normally make separations difficult. Highly acidic or basic solutions and concentrated salt mixtures are included in the matrices. Significant volume reductions can be achieved with SPE. Separations using SPE have been commercialized in both industrial and analytical applications.

A calorimetric titration study of uni-and bivalent metal ion interaction with several thia derivatives of 9-crown-3, 12-crown-4, 15-crown-5, 18-crown-6, 24-crown-8, and with several oxathiapentadecanes in water or water-methanol solvents at 25 °C

Abstract The interaction of several sulfur derivatives of crown-3, crown-4, crown-5, crown-6, crown-8, and three oxathiapentadecanes with Ag + , Hg 2+ , Tl + , and Pb 2+ in water or water-methanol solvents has been studied by a calorimetric titration procedure. The partial substitution of sulfur for oxygen in the crown-5 and crown-6 ligands results in little change in the affinity of the ligand for Tl + and Pb 2+ , but greatly increased affinity for Ag + and Hg 2+ . Values of log K, ΔH, and TΔS are reported where their determination was possible. Cation-ligand stoichiometries of 1:2 were found for Ag + and Hg 2+ complexes of many of the cyclic thia ethers. Only 1:1 complexes were found for Tl + and Pb 2+ .

Synthesis and chromatographic properties of polysiloxane stationary phases containing biphenylcarboxylate ester liquid-crystalline side groups

Abstract Ten new liquid-crystalline alkene compounds based on the biphenylcarboxylate ester have been prepared. Some of these alkenes, along with liquid-crystalline alkenes previously reported, were attached to polysiloxane polymers and tested as stationary phases in capillary column gas chromatography. The phase containing nearly 50% substitution with the biphenylcarboxylate ester side groups which were each separated from the polysiloxane backbone by a three-carbon and an ether- oxygen spacer proved to have the best chromatographic properties.

The synthesis of some substituted macrocyclic ether-ester compounds

Abstract A series of macrocyclic ether-esters has been prepared by treating various glycols with adipoyl chloride and various substituted malonyl, succinyl and glutaryl chlorides. The prepared compounds include: 15-ethyl- and 15-phenyl-1,4,7,10,13-pentaoxacyclohexadecane-14,16-dione ( 5 and 6 ); 15-methyl-, 15-phenyl-, cis -cyclohexo-[o]-and benzo-[o]-1,4,7,10,13-pentaoxacycloheptadecane-14,17-dione ( 7–10 ); trans,trans -1,4,7,10,13,18,21,24,27,30-de-caoxacyclotetratriacontane-15, 32-diene-14,17,31,34-tetraone ( 11 ); 1,4,7,10,13-pentaoxacyclooctadecane-14,18-dione ( 12 ); 15,15,16,16,17,17-hexafluoro- and 16-methyl-1,4,7,10,13-pentaoxacyclooctadecane-14,18-dione ( 13 and 14 ); 1,4,7,10-tetraoxacyclohexadecane-11,16-dione ( 15 ); and 1,4,7,10,13-pentaoxacyclononadecane-14,19-dione ( 16 ).

Proton-ionizable crown compounds : 5. Macrocycle-mediated proton-coupled transport of alkali metal cations in H2OCH2Cl2H2O liquid membrane systems

Abstract Alkali cation transport is studied using proton-ionizable macrocycle carriers of the 4-hydroxypyridine and pyridone types in a bulk H 2 OCH 2 Cl 2 H 2 O liquid membrane system as a function of source and receiving phase pH. A pyridone crown-6 type macrocycle containing an octyl substituent (3) transports Li + , Na + , K + , Rb + and Cs + from MOH solutions by a proton-coupled mechanism in which no co-anion is transported. In these cases, alkali cation transport increases exponentially with increasing source phase pH above pH 12. Generally, alkali cation transport at source phase pH 14 is higher when nitric acid is present (receiving pH = 1.5) than when it is absent. In competitive transport experiments with macrocycle 3 involving K + ) and one other alkali cation M + , K + is transported selectively over M + by 4.6 (Na + ), 2.7 (Rb + ) and 6.3 (Cs + ) fold when the source and receiving phase pH values are 14 and 7, respectively.

Enantiomer-selectivity of ion-selective electrodes based on a chiral crown-ether ionophore

Abstract A newly synthesized crown ether ionophore can differentiate between R-(+) and S-(-)-1-phenylethylammonium ions when incorporated into a plasticized PVC based electrode membrane, thus providing enantiomer-selectivity. Different membrane compositions were studied. The selectivity coefficient found was 0.71, independent of the membrane composition. This proves the robustness of the ISE method for testing the enantiomeric selectivity of newly synthesized ionophores. Selectivities of the new ionophore towards different hydrophilic cations were also determined.