Investigation of indole chalcones encapsulation in β-cyclodextrin: determination of stoichiometry, binding constants and thermodynamic parameters (original) (raw)
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Journal of inclusion phenomena and macrocyclic chemistry, 2018
Spectroscopic investigation supported by molecular modeling methods has been used to describe the inclusion complex of β-cyclodextrin (β-CD) with 1-Methyl-1-({2-[4-(trifluoromethyl)phenyl]-1,3-thiazol-4-yl}methyl) piperidinium chloride (1MPTMPC) in solution and in solid state. The formation of inclusion complex between the β-CD and the 1MPTMPC has been investigated both in solution and in the solid state. Solution-state complexation between the 1MPTMPC and β-CD was established using 1 H NMR spectroscopy and isothermal titration calorimetry (ITC). From the 1 H NMR spectroscopic studies, 1:1 complex stoichiometry was deduced with an association constant (K) of 925 M −1. Using an independent binding model, the ITC technique provides a K value of the same order with the one determined by NMR and the thermodynamic parameters ΔH, ΔS and ΔG which reveals driving forces involved during complex formation. The formation of the solid inclusion compound was confirmed by X-ray powder diffraction and differential scanning calorimetry. The most probable conformation of the inclusion complex obtained through a molecular docking investigation corroborates well to ROESY experiment.
Journal of Inclusion …, 1998
Using a simple molecular mechanics approach interaction energy profiles of simple probes (C, CH 4 , C 6 H 6 , H 2 O, NH + 4 , and HCOO − ) passing through the center of the β-CD ring cavity along the main molecular symmetry axis were first evaluated. Molecular Electrostatic Potential (MEP) values along the same path were also evaluated. The effect of the flexibility of the host β-CD molecule together with solute-solvent (H 2 O) interactions have been represented by averaging structures of MD calculations for β-CD alone and β-CD surrounded by 133 H 2 O molecules. The effect of various substitutions of β-CD has also been evaluated. Small symmetric hydrophobic probes (such as C, CH 4 , C 6 H 6 ) are predicted to form stable inclusion complexes with non-substituted and substituted β-CDs, the probe position typically being near the cavity center. The stability of the inclusion complexes will increase with increasing size and aliphatic character of the probe. Small polar and charged probes (such as H 2 O, NH + 4 , HCOO − ) are predicted to prefer the interaction with the solvent (water) in the bulk phase rather than the formation of inclusion complexes with non-substituted and substituted β-CDs. Guest-host interactions in the stable inclusion complexes with hydrophobic probes are almost entirely dominated by dispersion interactions. The MEP reaches magnitudes close to zero in the center of the non-substituted β-CD ring cavity and in most of the studied substituted β-CDs and shows maximum positive or negative values outside of the cavity, near the ring faces. Substitution of β-CD by neutral substituents leads to enhanced binding of hydrophobic probes and significant changes in the MEP profile along the β-CD symmetry axis.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2024
We prepared a naturally occurring flavanoid namely quercetin from tea leaves and analyzed by Absorption, Emission, FT-IR, 1H, 13C nmr spectra and ESI-MS analysis. The inclusion behavior of quercetin in cyclodextrins like α-, β-, γ-, per-6-ABCD and mono-6-ABCD cavities were supported such as UV–vis., Emission, FT-IR and ICD spectra and energy minimization studies. From the absorption and emission results, the type of complexes formed were found to depend on stoichiometry of Host:Guest. FT-IR data of CD complexes of quercetin supported inclusion complex formation of the substrate with α-, β- and γ-CDs. The inclusion of host–guest complexation of quercetin with α-, β-, γ-CDs, per-6-ABCD and mono-6-ABCDs provides very valuable information about the CD:quercetin complexes, the study also shows that β-CD complexation improves water solubility, chemical stability and bioavailability of quercetin. Besides, phase solubility studies also supported the formation of 1:1 drug-CD soluble complexes. All these spectral results provide insight into the binding behavior of substrate into CD cavity in the order per-6-ABCD > Mono-6-ABCD > γ-CD > β-CD > α-CD. The proposed model also finds strong support from the fact with excess CD this exciton coupling disappears indicates the formation of only 1:1 complex.
Density‐functional‐theory study of α‐cyclodextrin inclusion complexes
We apply the density functional theory on the description of the a-cyclodextrin (a-CD) and the analysis of the molecular electrostatic potential (MEP) for complexes of this system with Na þ , F À , CO 2À 3 , and N,N-dimethyl formamide, as substrates. Four exchange-correlation functionals were considered: one of the local density approximation, two of the generalized gradient approximation (BLYP and PBE), and one of the hybrid family. These exchange-correlation functionals were coupled with the DZVP/A1, DZVP, and TZVP basis set functions. All complexes were fully optimized by all methods. The experimental molecular structure of the a-CD compares better with that described by the PBE exchange-correlation functional. The MEP analysis shows that the electrostatic is quite relevant on the intermolecular interaction for the a-CD complexes in gas phase. Some of our results are in disagreement with those published previously with the PM3 semiempirical method and the B3LYP//PM3 method.
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2013
The inclusion complex of b-cyclodextrin (b-CD) and diphenylamine (DPA) was investigated by using PM3MM, DFT, HF and ONIOM2 methods. The most stable structure was obtained at the optimum position and angle. The results indicate that the inclusion complex formed by DPA entering into the cavity of b-CD from its wide side (the secondary hydroxyl group side) is more stable than that formed by DPA entering into the cavity of b-CD from its narrow side (the primary hydroxyl group side). The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of natural bonding orbital (NBO) analysis, employed to quantify the donor-acceptor interactions between diphenylamine and b-CD. A study of these complexes in solution was carried out using the CPCM model to examine the influence of solvation on the stability of the diphenylamine b-CD complex.
Thermochimica Acta, 2012
An approach mainly based on thermogravimetric analysis (TGA) was developed to evaluate the stoichiometric ratio (SR, guest to host) of the guest-␣-cyclodextrin (Guest-␣-CD) inclusion complexes (4cresol-␣-CD, benzyl alcohol-␣-CD, ferrocene-␣-CD and decanoic acid-␣-CD). The present data obtained from Fourier transform-infrared (FT-IR) spectroscopy showed that all the ␣-CD-based inclusion complexes were successfully prepared in a solid-state form. The stoichiometric ratios of ␣-CD to the relative guests (4-cresol, benzyl alcohol, ferrocene and decanoic acid) determined by the developed method were 1:1, 1:2, 2:1 and 1:2, respectively. These SR data were well demonstrated by the previously reported X-ray diffraction (XRD) method and the NMR confirmatory experiments, except the SR of decanoic acid with a larger size and longer chain was not consistent. It is, therefore, suggested that the TGA-based method is applicable to follow the stoichiometric ratio of the polycrystalline ␣-CD-based inclusion complexes with smaller and shorter chain guests.
Theoretical Chemistry Accounts, 2019
Most of the researches in supramolecular chemistry area are focused on the conventional hydrogen bonds without taking into account unconventional intermolecular interactions. The nature and strength of the conventional and unconventional interactions in inclusion complexes formed between neutral aspirin (ASA) and its deprotonated form (ASA −) with β-cyclodextrin (β-CD) have been studied. It was conducted through combining atoms in molecules (AIM) theoretical criteria suggested by Koch and Popelier and natural bond orbital (NBO) analyses by means of dispersion-corrected density functional theory (DFT-D3) with the functional B3LYP using cc-pvdz basis set in the gas phase. We have found five intermolecular closedshell interaction groups responsible for neutral ASA:β-CD and deprotonated ASA − :β-CD inclusion complexes stability: One is conventional O-H•••O bond group.
Inclusion complexes of spin-labeled indoles with cyclodextrins in aqueous solutions
Russian Chemical Bulletin, 2005
Guest host complexes of β and γ cyclodextrins (CDs) with two spin labeled indole de rivatives having the same molecular weights but different structures were studied by EPR spectroscopy in aqueous solutions and semiempirical quantum chemical calculations of these systems were carried out. In the presence of CD the polarity of the NO group environment decreases and the rotational correlation time (τ) of guest molecules increases. Both indole derivatives form 1 : 1 complexes with γ CD, the binding constants of the complexes being different more than twice. Simulation of EPR spectra made it possible to determine the indole ring orientation relative to the plane of the host molecule (at angles in the range 30-60°) and the rotational diffusion coefficients of the complexes, which corresponded to the hydro dynamic volume of one γ CD molecule. In contrast to the complexes with γ CD the rotational correlation times, τ, of the complexes with β CD correspond to a hydrodynamic volume which much exceeds the volume of a single β CD molecule. The complexes with β CD are also characterized by more hydrophobic environment for guest molecules and absence of spin exchange with Ni 2+ ions in the aqueous solution. There results are consistent with a dimeric structure of β CD in the complex and with the orientation of the long axis of the guest molecule along the dimer axis. The energies and geometric parameters were calculated for all complexes by the PM3 method with a conventional set of parameters. The optimized energeti cally stable structures of the 1 : 1 complexes with γ CD and of the 1 : 2 complexes with β CD are consistent with experimental data.