ABSTRACT
A new templating motif for the formation of [2]pseudorotaxanes is described in which rigid, Y-shaped axles with an imidazolium core and aromatic substituents at the 2-, 4- and 5-positions interact with [24]crown-8 ether wheels ([24]crown-8 and dibenzo[24]crown-8). The Y-shape of the axle significantly enhances the association between axle and wheel when compared to simple imidazolium cations.
ABSTRACT
A new templating motif for the formation of [2]pseudorotaxanes is described in which T-shaped axles with a benzimidazolium core and aromatic substituents at the 2-, 4-, and 7-positions interact with [24]crown-8 ether wheels ([24]crown-8, dibenzo[24]crown-8, and dinaphtho[24]crown-8). The T-shape greatly enhances the association between axle and wheel when compared to simple imidazolium or benzimidazolium cations. A series of interpenetrated molecules are characterized by (1)H NMR spectroscopy and single crystal X-ray crystallography.
ABSTRACT
We report the Cl(-) transport activity for three imidazolium-based transporters. We present significant findings regarding the use of α-cyclodextrin and cucurbit[7]uril macrocycles to form inclusion complexes with these salts and to inhibit their membrane activity.
Subject(s)
Cell Membrane/metabolism , Chlorides/chemistry , Imidazolines/chemistry , Salts/chemistry , Anions/chemistry , Anions/metabolism , Biological Transport , Bridged-Ring Compounds/chemistry , Bridged-Ring Compounds/metabolism , Buffers , Cell Membrane/chemistry , Cell Membrane Permeability , Chlorides/metabolism , Hydrogen-Ion Concentration , Imidazoles/chemistry , Imidazoles/metabolism , Imidazolines/metabolism , Magnetic Resonance Spectroscopy , Salts/metabolism , Solutions/chemistry , alpha-Cyclodextrins/chemistry , alpha-Cyclodextrins/metabolismABSTRACT
N,N'-Dialkyl-(1,4-phenylene)bisimidazolium salts form inclusion complexes with cucurbit[7]uril (CB[7]) with high association constants. The stoichiometry of the complexes depends on the alkyl chains and on the relative concentration of the imidazolium salt and CB[7]. The binding interactions of CB[7] with these bisimidazolium salts were studied experimentally by (1)H NMR, high resolution mass spectroscopy, and UV spectroscopy, and theoretically by semiempirical molecular modeling. Nonlinear regression analysis was used to calculate or estimate the binding parameters for the supramolecular inclusion complexes present in solution. The detailed study of the binding association of these imidazolium salts may allow us to understand the exact role of each recognition site in these salts and to assemble higher supramolecular complexes.
ABSTRACT
N, N'-Disubstituted methylenediimidazolium bromide salts substituted with two aromatic groups present two different binding sites. In the binary complexes with cyclodextrins (CDs) or cucurbit[7]uril (CB[7]), the macrocycle is always positioned on the external aromatic residues. In the ternary complexes, CB[7] is positioned around the diimidazolium cation, where the external aromatic residue is included in the CD's cavity. The unfavored position of the CB[7] on the cationic site in the ternary complex is the result of its cooperative supramolecular interaction with the cyclodextrin. The obtained ternary complexes possess different interfacial properties, compared to those of the binary complexes. We demonstrate these hypotheses by NMR spectroscopy, ESI-HRMS spectrometry, molecular modeling simulation, and surface tension measurements.
ABSTRACT
N,N'-Disubstituted methylenediimidazolium salts allow the formation of flexible inclusion complexes with beta-cyclodextrin, cucurbit[7]uril, tetrapropoxycalix[4]arene, and dibenzo-24-crown-8 ether. Due to the salt nature of the imidazolium guest, the counterion largely determines its solubility in a given solvent. Moreover, by the judicious choice of the imidazolium substituents, inclusion complexes of guest salts were obtained with a variety of macrocyclic hosts, and the binding parameters of the inclusion were determined for each complex.
