Fluorescence correlation spectroscopy, a tool to investigate supramolecular dynamics: inclusion complexes of pyronines with cyclodextrin (original) (raw)
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Supramolecular host-guest complexes between coumarin 460 and cyclodextrins: a matter of size
The role of the host size on stoichiometry, structure and strength of supramolecular association between a fluorescent probe, coumarin 460 (C460), and the three natural cyclodextrins (CDs) with increasing cavity sizes (α, β fluorescent probe, coumarin 460 (C460), and the three natural cyclodextrins (C s) with increasing cavity si es (α, β and γ-cyclodextrin) is analyzed, using fluorescence spectroscopy. The variations of the fluorescence emission spectra of C460 with CD concentration can be explained with a 1:1 complexation equilibrium model for α-CD and β-CD, but also a 1:2 complex has to be included in the case of γ-CD. Nevertheless, the photophysical properties and the stability of the complexes do not correlate in a simple way with the cavity size. For instance, the association between y p p y y , C460 and β-CD, which is the CD with medium cavity size, is much stronger than with the other CDs but it does not provoke fluorescence enhancement as in those cases. Detailed analysis o...
The possibilityofusingpyreneasa fluorescentprobeinamodelchemosensorcomposedof β-cyclo- dextrin–pyrene(Py–βCD) complexinaqueoussolutionwasstudiedinthepresenceofseveralanalytes (A) ofdifferentpolarity.AbsorptionbandsthatprovetheformationoftheaggregatedPy–βCD complex werefoundintheUV–VIS spectraofaqueoussolutionofpyrenewithadded βCD. Theaggregatesizeas measured bydynamiclightscatteringwasfoundtohaveavalueof3.2–3.6 nm.Theaggregatewas identified asa1:2complexofPywith βCD (Py@2βCD) surroundedbytwoempty βCD molecules.The ratio I3/I1 of intensity I3 of thethirdvibronicbandat 26,000cm1 in the fluorescence spectrumto intensity I1 of the0–0 transitionat 26,800cm1 wasusedasananalyticalcharacteristicofthe fluorescent probe.Thevalueof I3/I1 for Py@2βCD ishighlysensitivetothepresenceofseveral μM of analyteinaqueoussolution,andthisvalueismarkedlyhigherthanthatforpyreneinsolution. & 2016ElsevierB.V.Allrightsreserved
Specific interactions in the inclusion complexes of pyronines Y and B with beta-cyclodextrin
The journal of physical chemistry. B, 2005
The aim of this work is to analyze the role of specific interactions in host-guest association processes. The formation of inclusion complexes between pyronines Y and B and beta-cyclodextrin and the nature of the interactions involved have been studied using absorption, steady-state fluorescence, and time-resolved fluorescence spectroscopies. The two pyronines form 1:1 complexes with beta-cyclodextrin, with the association equilibrium constant being much higher in the case of pyronine B. Complexation causes a slight red shift of the emission spectra of the pyronines but decreases significantly their fluorescence quantum yields and lifetimes. To explain this atypical behavior, the photophysical properties of the pyronines in different solvents were determined and compared with those of the complexes. The similarities observed between the pyronines in dioxane and in the interior of the cyclodextrin cavity suggest that there are important specific interactions of the pyronines with the...
Fluorescence Dynamics of Monocyclodextrin– and Bis(thiol‐cyclodextrin)–Coumarin C153 Complexes
ChemPhysChem, 2015
The solvation and confinement of coumarin C153 within supramolecular host/guest complexes based on β‐cyclodextrin (β‐CD) and 6‐deoxy‐6‐thio‐β‐cyclodextrin (β‐CD‐SH) in water are studied by fluorescence spectroscopy. For β‐CD/C153, the 1:1 complex is proposed, and for β‐CD‐SH/C153 both the 1:1 and 2:1 complexes are believed to be formed. The 2:1 β‐CD‐SH/C153 complex has an association constant of 4.2×105 M−1 and a C153 population of 82 %, which are interestingly high values, indicating that the proposed β‐CD‐SH dimers structure are connected by covalent disulfide bonds; this is supported by mass spectrometry. Solvation related to fast hydrogen‐bond rearrangement as a part of fluorescence relaxation is determined by the ultrafast components of time‐resolved spectroscopy to be 3 and 7 ps for the 1:1 β‐CD/C153 and 2:1 β‐CD‐SH/C153 complexes, respectively.
Evidence of cyclodextrin aggregation obtained with Fluorescence Correlation Spectroscopy
2010
We have studied the complexation between an adamantane derivative labelled with the fluorescent probe Alexa 488 and the three natural cyclodextrins (-, and -CD) by Fluorescence Correlation Spectroscopy (FCS), demonstrating the ability of this technique to detect association and to determine the corresponding equilibrium constants with no need for changes in the fluorescence properties of the guest. At low CD concentrations the observed increase of the diffusion time of the probe is mainly due to the complexation of the adamantyl moiety, but further changes are observed when increasing CD concentration that are attributed to the formation of CD aggregates. These aggregates appear at quite low CD concentrations and seem to be formed by a small number of CD molecules. These results show the potential of FCS for the study of CD self-assembly, a recently-recognized phenomenon that could be used to improve certain applications of CDs.
The Journal of Physical Chemistry, 1995
A 1 : 1 complex of 6-O-a-~-glucosyl-~-cyclodextrin (GI-B-CD) with 4-(dimethy1amino)benzonitrile (DMABN) associates with itself in aqueous solutions at high concentrations into a 2:2 complex (homodimer). The 1:l complex of GI-B-CD with DMABN also makes a heterodimer (1:1:2 complex) by the association with a 1:l inclusion complex of another guest molecule such as 1-pentanol, benzene, anisole, and benzonitrile. The association of the complex is accompanied by a drastic change in the fluorescence spectrum of DMABN. The measurement of the fluorescence intensity as a function of the concentration of GI-B-CD gave the equilibrium constants for the association. The equilibrium constants were greatly dependent on the temperature, and the values for both AH and AS were largely negative. The fluorescence spectra of DMABN in the cavity of the dimers changed with exchanging the second guest compound, which implies that the second guest molecule plays the role of a polar solvent in the nonpolar environment in the cavity. The formation of homo-and heterodimers of the 1:l inclusion complex also takes place in the solutions containing other cyclodextrins and DMABN.
Inclusion complexes of dyes and cyclodextrins: modeling supermolecules by rigorous quantum mechanics
The results of structure optimization and molecular dynamics simulation of host-guest γ -cyclodextrin-pinacyanol dye inclusion complexes are obtained by applying a density functional based tight-binding code. The results attempt to correlate UV/Vis and circular dichroism spectral data with calculated aggregate structures of the sandwich dimer, with the monomers twisted slightly against each other. The sense of twist is predetermined by the chirality of the complexing host. The UV/Visspectral are interpreted using the exciton model. Within this model, each excited state of the monomer generates two excitonic states in the dimer. The interaction between the two monomers results then in a Davydov splitting of the two dimer states. The opposite signs of the two dimer states can be attributed to the twist of the monomers when they interact.