Stephen L. De Wall

Experimental Evidence for Alkali Metal Cation−π Interactions

The interaction of alkali metal ions with arenes such as benzene or substituted benzenes has been documented in a variety of ways. This paper reviews the experimental evidence that has been accumulated to document the cation-π interaction that occurs between arenes and, particularly the ions sodium and potassium.

Macrocyclic polyethers as probes to assess and understand alkali metal cation-π interactions

Abstract Cation-π interactions of alkali metals with arenes have been known in the gas phase for two decades but solid-state structural data have become available only recently. The quest for solid-state evidence is described here. Complexation of Na+ and K+ by arene-terminated lariat ethers has provided important insights into the cation-π interaction.

Syntheses and aggregate study of bisphenol-containing diaza-18-crown-6 ligands

Abstract Bisphenol-containing diaza-18-crown-6 ligands (1–16) were synthesized as potential membrane-forming amphiphilesvia the one-pot Mannich reaction. Sonication of the crude products in a small amount of MeOH followed by filtration and drying proved to be an efficient method of purifying nearly all compounds. Compounds8 and9 were selected for assay as amphiphiles. Compared to simple, alkylated diazacrown ethers, the stability of the amphisomes formed from these monomers is lower possibly because intramolecular hydrogen bonding prevents formation of intermolecular hydrogen bonds. Bisphenol-containing diaza-18-crown-6 ligands (1–16) were synthesized as potential membrane-forming amphiphiles. Download : Download full-size image

Aggregate formation from 3-alkylindoles: amphiphilicmodels for interfacial helix anchoring groups

Indole can function as an amphiphile headgroup, but the counter-intuitive observation that 3-substituted indoles form less stable aggregates than the N-substituted isomers has been addressed by use of a Langmuir–Blodgett trough.

Intermolecular axial solvation of bound cations by sidearm donor groups in lariat ethers: formation of a supramolecular network

Abstract Previously studied disubstituted 4,13-diaza-18-crown-6 derivatives, R N18N R, in which the substituents were cyanomethylor propargyl did not show intramolecular, lariat-type cation solvation. The ring-bound cation in the propargyl derivative issolvated by the six macroring heteroatoms and apically by a bifurcated interaction of the type F···K + ···F. In contrast, when thesidearm is cyanoethyl, an extended intermolecular network forms when the bound cation is either Na + or K + .

N,N-Didansyl-4,13-diaza-18-Crown-6: A Fluorescence-sensitive, Weakly Complexing Macrocycle Used to Probe the Phospholipid Vesicle Environment

N, N-Didansyl-4, 13-diaza-18-crownh-a6s been prepared and characterized by standard chemical techniques. The fluorescence emission of the dansyl sidearms are sensitive to the environment and the macrocycle has been used to probe the interior of a phospholipid bilayer. An experiment to probe the environment experienced by metal cation complexes of this macrocycle failed, apparently due to its extremely low cation binding strength. This macrocycle was also ineffective in transporting Na+ through a bulk CHC13 membrane. A solid state structure of the free macrocycle suggests why binding is so poor for this compound.

Sodium cation complexation in a macrocycle containing thymines as sidearm donor groups

AbstractPrevious studies of macrocycles having alkyl sidearms terminated in adenine or thymine have been focused on intermolecular association. Electrospray mass spectrometric analyses suggested that sodium complexation could be a major alternative process in the presence of the appropriate cation. Sodium cation complexation by N,N′-bis(3-(1-thyminyl)propyl)-4,13-diaza-18-crown-6 has been confirmed by X-ray crystallographic analysis. A sodium cation is bound in the center of the macroring. The four ether oxygens and two thyminyl carbonyl donors have the shortest contacts with the two, macroring nitrogen atoms being somewhat more remote. Neither the iodide counterion nor an acetone of solvation appears to interact with the sodium cation. Crystal Data: Triclinic,

Synthetic, Sodium-Ion-Conducting Tris(Macrocycle) Channels that Function in a Phospholipid Bilayer Membrane: An Overview

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