Thermodynamic Studies on the Cyclodextrin Complexation of Aromatic and Aliphatic Guests in Water and Water−Urea Mixtures. Experimental Evidence for the Interaction of Urea with Arene Surfaces

Godı́nez, Luis A.; Schwartz, L.; Criss, Cecil M.; Kaifer, Ángel E.

doi:10.1021/jp970359i

Cited by 70 publications

(65 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…From the equilibrium constants for these host-guest systems the Gibbs free energy difference DG = RT lnK diss can be derived, which gives a rough estimate of the related binding energies of DG % À28 kJ mol À1 (ammonium) and DG % À38 kJ mol À1 (trimethyl ammonium). These values for DG correspond well with calorimetric or NMR spectroscopic data obtained for related supramolecular systems, such as cyclodextrins [23,29] and watersoluble cavitands. [30] This aspect is important for two reasons: 1) it shows that AFM force spectroscopy can be used to investigate single-molecule affinity interactions in a broad affinity range of ten orders of magnitude (10 À15 m (biotinstreptavidin) to 10 À5 m (this work)), and 2) that this technique allows the estimation of equilibration constants and related binding energies of single (supra)molecular complexes.…”

supporting

confidence: 85%

Supramolecular Chemistry at the Single‐Molecule Level

et al. 2004

View full text Add to dashboard Cite

In supramolecular chemistry [1] synthetically designed organic constituents interact noncovalently, in a directed and specific way to form host-guest complexes of higher complexity. The ability to tailor the molecular interplay with respect of chemical design, specificity, and molecular switching opens up the development of new molecular materials for artificial molecular recognition, molecular organization, and selfassembly. We have used mechanical single-molecule force spectroscopy to investigate the binding of individual resorc-[4]arene-ligand host-guest complexes. By using diluted samples of the host and guest molecules that are modified with a long linker which is attached to an atomic force microscope (AFM) tip, we were able to prevent multiple binding and to observe single host-guest unbinding events in a supramolecular system for the first time. The molecular binding forces, their dependence on external loading rates, the rate of dissociation, and the molecular cavity length directly relate to the molecular properties of the supramolecular species and are consistent with an activated decay of a metastable bound state, a finding already established for biological receptor-ligand complexes. This result allows new insights into the mechanisms, kinetics, and thermodynamics of intermolecular association in chemistry and biology, and opens new possibilities in the investigation, design, and development of synthetic receptor systems.Calixarenes are model receptor systems providing synthetic receptor cavities for the inclusion of small cationic guests, such as alkali-metal or ammonium ions. [2][3][4][5] Organic cations, such as ammonium ions, play a significant role in molecular recognition processes in nature (e.g. in protein side chains). Calix[n]arenes, generally, are a class of macrocyclic compounds formed by the base-catalyzed condensation of nphenol derivatives and formaldehyde. [2,3] The resorc [4]arenes [6,7] considered herein are calixarenes formed from four

show abstract

supporting

confidence: 85%

Supramolecular Chemistry at the Single‐Molecule Level

et al. 2004

View full text Add to dashboard Cite

show abstract

“…Actually, we have investigated the inhibition of altro-b-CD tumbling using a competitive guest, adamantane carboxylic acid sodium salt, which is strongly included in the cavity of b-CD. 39,[48][49][50][51][52] Mixing 100 equivalents of adamantane carboxylic acid sodium salt guest molecules with a PDIC 7 -3bCD 2 aqueous solution decreases the emission intensities of PDIC 7 -3bCD 2 (Supplementary Figure S29). The addition of an excess of adamantane carboxylic acid sodium salt into a PDIC 7 -3bCD 2 aqueous solution causes a marked decrease in the emission intensity, which is 61% of the initial intensity.…”

Section: Resultsmentioning

confidence: 99%

Emission properties of cyclodextrin dimers linked with perylene diimide—effect of cyclodextrin tumbling

Takashima

Otsubo

et al. 2012

Polym J

View full text Add to dashboard Cite

Perylene diimide (PDI) derivatives with cyclodextrins (PDI-CD 2 s) exhibit specific emission properties, which depend on the type of CDs in an aqueous solution. Herein we successfully create an emission film-kneaded PDI-CD 2 derivatives via effective tumbling of the altropyranose unit. PDI-6CD 2 s are crosslinked with PDI between 6-amino-CDs. Although the emission intensities of PDI-6CD 2 s in dimethyl sulfoxide are similar regardless of the type of CD, PDI-6cCD 2 has a relatively high emission intensity in aqueous solutions. In contrast, for PDIC 7 -3CD 2 s, which are linked with N,N'-bis(6-carboxylhexyl)perylene-3,4,9,10-tetracarboxyl diimide (BisC 7 -PDI) between 3-amino-CDs, the emission intensity of PDIC 7 -3bCD 2 is stronger than those of PDIC 7 -3aCD 2 , PDIC 7 -3cCD 2 , and PDI-6CD 2 s in aqueous solutions. The selective emission behavior of PDIC 7 -3CD 2 s is due to the formation of the pseudo[1]rotaxane dimer through tumbling of the altropyranose unit in an aqueous solution. PDIC 7 -3bCD 2 in the solid state does not demonstrate a distinctive emission due to self-quenching, whereas PDIC 7 -3bCD 2 kneaded into the polyvinyl alcohol (PVA) film exhibits a bright yellow emission. The order of the emission intensities of PDIC 7 -3CD 2 s kneaded into PVA films is similar to those in aqueous solutions. INTRODUCTIONRecently, supramolecular assemblies with extended aromatic compounds have attracted much attention. 1-4 Perylene diimides (PDIs) derivatives effectively form supramolecular assemblies through p-p stacking interaction. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] In particular, supramolecular assemblies based on calixarenePDI conjugates show efficient energy and electron transfer properties due to the well-defined rigid and electron-rich scaffolds of calixarenes. [22][23][24][25][26][27] We have prepared PDI derivatives with a high emission property in aqueous solutions.Generally, PDI derivatives have low solubilities in aqueous solutions. Even if PDI derivatives are dissolved in aqueous solutions by introducing a hydrophilic group, the emission of PDI derivatives exhibit self-quenching in aqueous solutions due to the formation of supramolecular assemblies and folders. To create water-soluble and effective emission sensor materials with PDI derivatives, we have introduced CDs into the PDI motif. The CDs are a family of macrocyclic oligosaccharides; the most common are composed of 6 (a), 7 (b), or 8 (g) a-1,4-linked D-glucopyranose units. [28][29][30][31][32][33][34] The introduction of CDs should influence the molecular recognition property and increase the emission intensity. Although supramolecular assemblies based on permethylated CDPDI conjugates have been previously reported, 35-38 the formation of assemblies cannot prevent the decrease in the monomer emission intensity of the PDI units due

show abstract

“…Urea affects the structure of water [10] and has been termed an "antihydrophobic agent" [11]. With regard to the formation of b-CD analyte complexes, a decrease in the complexation constants upon addition of urea has been observed in most of the cases [9,[11][12][13] although the increase of the binding constant between b-CD and naphthalene carboxylic acid has also been reported [12]. However, the actual effect of urea on chiral separations has not yet been studied in more detail.…”

Section: Introductionmentioning

confidence: 99%

Influence of buffer substances and urea on the β‐cyclodextrin‐mediated chiral separation of dipeptides in CE

Hammitzsch-Wiedemann¹,

Scriba²

2007

Electrophoresis

View full text Add to dashboard Cite

The influence of buffering substances and urea on the beta-CD-mediated chiral separations of the dipeptides Ala-Phe and Ala-Tyr was studied in the pH range of 2.5-3.8. Only minor effects of the buffer substances on the chiral separation selectivity alpha were observed at a beta-CD concentration of 15 mg/mL. In contrast, the selectivity improved at pH 2.5 but decreased at pH 3.8 upon the addition of 2 M urea. Complexation by beta-CD resulted in a shift of the pK(a) values toward higher values which was more pronounced for the DD-enantiomers of both dipeptides than for the LL-enantiomers. Addition of urea further increased the pK(a) shift. The consequence of this pK(a) shift is an increase of the fraction of the protonated, positively charged form of the peptides which explained the improved chiral separation at pH 2.5 and the reduced selectivity at pH 3.8. A pK(a) shift by the addition of urea was also observed for N-tert-butyloxycarbonyl phenylalanine (BOC-Phe) as a model compound that is strongly complexed by beta-CD. This effect was not stereospecific. Addition of urea resulted in a decrease of the apparent complexation constants between beta-CD and the BOC-Phe enantiomers to the same extent but this did not affect the separation selectivity alpha. For chiral separations that display strong pH dependence such as peptide enantioseparations close to the pK(a) values of the compounds, urea may not solely be regarded as a solubility enhancer for beta-CD but may also influence the separation.

show abstract

Thermodynamic Studies on the Cyclodextrin Complexation of Aromatic and Aliphatic Guests in Water and Water−Urea Mixtures. Experimental Evidence for the Interaction of Urea with Arene Surfaces

Cited by 70 publications

References 32 publications

Supramolecular Chemistry at the Single‐Molecule Level

Supramolecular Chemistry at the Single‐Molecule Level

Emission properties of cyclodextrin dimers linked with perylene diimide—effect of cyclodextrin tumbling

Influence of buffer substances and urea on the β‐cyclodextrin‐mediated chiral separation of dipeptides in CE

Contact Info

Product

Resources

About