Binding Constants Of Inclusion Complexes Research Articles

Inclusion complexation of novel synthesis amino acid based ionic liquids with β-cyclodextrin

Inclusion complex formation between amino acid based ionic liquids (AAILs) i.e., 1-(2-(octylamino)-2-oxoethyl)pyridin-1-ium bromide and 4-((hydroxyimino)methyl)-1-(2-(octylamino)-2-oxoethyl)pyridin-1-ium bromide into β-cyclodextrin have been investigated in solution. The inclusion complexes (ICs) of AAILs with β-CD were synthesized through the co-precipitation method. The solid IC formation is characterized by numerous analytical techniques, primarily by UV–vis spectroscopy and secondary by major techniques i.e., FT-IR and 1H NMR. The binding constant and 1:1 stoichiometric of ICs nature of the complex between AAILs and β-CD in solution were determined by Job's plot method using UV–vis spectroscopy. As results suggest, the binding constants of ICs are higher for OAOEPB-β-CD as compared to HIMOAOEPB-β-CD. The different thermodynamic parameters such as change in standard Gibbs free energy (ΔG0), standard enthalpy changes (ΔH0) and standard entropy change (ΔS0) have been estimated with the help of van't Hoff equation. Noteworthy changes of IR stretching frequency also support the IC formation. 1H NMR results suggest that the tail part of AAILs is more suitably included inside the hydrophobic cavity of β-CD and it shows 1:1 stoichiometric ICs formation.

2,6-Dinitroaniline and β-cyclodextrin inclusion complex properties studied by different analytical methods

The formation of supramolecular host-guest inclusion complex of 2,6-Dinitroaniline (2,6-DNA) with nano-hydrophobic cavity of β-cyclodextrin (β-CD) in solution phase were studied by UV-visible spectrophotometer and electrochemical method (cyclic voltammetry, CV). The prototropic behaviors of 2,6-DNA with and without β-CD and the ground state acidity constant (pKa) of host-guest inclusion complex (2,6-DNA-β-CD) was studied by Spectrophotometrically. The binding constant of inclusion complex at 303K was calculated using Benesi–Hildebrand plot and thermodynamic parameter (ΔG) were also calculated. The solid inclusion complex formation between β-CD and 2,6-DNA was confirmed by 1H NMR, FT-IR, XRD and SEM analysis. The β-CD:2,6-DNA inclusion complex obtained by molecular docking studies is in good correlation with the results obtained through experimental methods.

Study of inclusion complex between 2,6-dinitrobenzoic acid and β-cyclodextrin by 1H NMR, 2D 1H NMR (ROESY), FT-IR, XRD, SEM and photophysical methods

The formation of host–guest inclusion complex of 2,6-dinitrobenzoic acid (2,6-DNB) with nano-hydrophobic cavity of β-cyclodextrin (β-CD) in solution phase has been studied by UV–visible spectroscopy and electrochemical analysis (cyclic voltammetry, CV). The effect of acid–base concentrations of 2,6-DNB has been studied in presence and absence of β-CD to determination for the ground state acidity constant (pKa). The binding constant of inclusion complex at 303K was calculated using Benesi–Hildebrand plot and thermodynamic parameter (ΔG) was also calculated. The solid inclusion complex formation between β-CD and 2,6-DNB was confirmed by 1H NMR, 2D 1H NMR (ROESY), FT-IR, XRD and SEM analysis. A schematic representation of this inclusion process was proposed by molecular docking studies using patch dock server.

Spectral Studies on the Supramolecular Assembly of 1H2NA: β-CD Complex and its Analytical Application as Chemosensor for the Selective Sensing of Cr3+

The supramolecular assembly of 1-hydroxy-2-naphthoic acid (1H2NA) with β-CD has been investigated by UV-visible and fluorescence spectroscopy. The stoichiometry and binding constant of inclusion complex was estimated using the Benesi–Hildebrand plot derived from the excitation and emission spectral data at 303 K. The estimated ΔG indicated that the inclusion is an exergonic and spontaneous process. The mechanism of complexation was investigated and confirmed by FTIR spectroscopy, semiempirical, and molecular docking studies. During the investigation of complexation, significant increase in the fluorescence intensity for the variation of β-CD concentration was observed. Based on this phenomena the chemosensory power of 1H2NA: β-CD complex was investigated thoroughly for various metal ions and we found the emission of complex showed a drastic increase in the intensity for Cr3+ and the fluorescence intensity enhanced to >50 out of all the metal ions studied. The order of change of fluorescence intensities found to be, Cr3+ > Se4+ > Ni2+ > K+ > Th4+ > Ca2+, Ti4+ > Al3+ > Ce4+ > Mg2+ > Ag+ > Na+ > Fe3+. Selectivity and sensitivity analysis showed remarkable selectivity in sensing Cr3+ with the LOD of 0.3 × 10−4 M and LOQ of 0.9 × 10−4 M.

The investigation of inclusion behavior of Solvent Violet 9 with 4-sulfonatocalix[n]arenes and its recognition to DNA

The inclusion behavior of Solvent Violet 9 (SV9) with 4-sulfonatocalix[n]arenes (SCXn) (n=4,6,8) was investigated at various pH values by ultraviolet–visible spectroscopy. SV9 is able to form an inclusion complex with calixarenes. Different absorption behaviors were observed for the dye with the various host calixarenes. The molecular binding abilities were affected by the configuration of the calixarene cavities and the solution pH. Various experimental conditions, including calixarenes concentrations, were investigated and the results suggested that the three calixarene were most suitable for inclusion of the dye at pH=3.05. The formation constant could be calculated. The inclusion behavior of the complexes was studied in detail using nuclear magnetic resonance spectroscopy. Finally, the interactions of SV9 with Salmon testes DNA in SCXn supramolecular system were studied by UV–Vis absorption spectroscopy. The UV–Vis absorption show that the interaction of SV9 with DNA depends on the concentration ratio of SV9 to DNA and the pH values. The binding constants of inclusion complexes with DNA are calculated. It was observed that SCXn can affect the interactive mode of SV9 with DNA.

Determination of Binding Constants for Inclusion Complexes of Cyclodextrins with Organic Solvents, Ethylene Glycol, and Its Related Compounds by Means of 1H NMR Spectroscopy

Abstract The binding constants (Ka’s) for the complexation of α- and β-cyclodextrins (α- and β-CDs) with some hydrophilic organic solvents such as methanol, dimethyl sulfoxide, acetone, etc., were successfully determined in D2O by following changes in the 1H NMR chemical shift of the C(3)–H signal of CD, using the C(1)–H signal as an internal reference. The Ka value obtained for a β-CD–methanol complex was 0.088 mol−1 dm3 at 298 K, which is, as we know, the smallest among Ka’s measured thus far for CD complexes. The same method was also applied to the determination of Ka’s for the complexation of α-CD with ethylene glycol and some related compounds. It was revealed that these molecules were certainly included within the cavity of α-CD, though the Ka values are fairly small.

Spectral and electrochemical study of host–guest inclusion complex between 2,4-dinitrophenol and β-cyclodextrin

The formation of host–guest inclusion complex of 2,4-dinitrophenol (2,4-DNP) with nano-hydrophobic cavity of β-cyclodextrin (β-CD) in solution phase was studied by UV–visible spectrophotometer and electrochemical method (cyclic voltammetry, CV). The prototropic behaviors of 2,4-DNP with and without β-CD and the ground state acidity constant (pKa) of host–guest inclusion complex (2,4-DNP–β-CD) were studied. The binding constant of inclusion complex at 303K was calculated using Benesi–Hildebrand plot and thermodynamic parameter (ΔG) was also calculated. The solid inclusion complex formation between β-CD and 2,4-DNP was confirmed by 1H NMR, FT-IR, XRD and SEM analysis. A schematic representation of this inclusion process is proposed by molecular docking studies using PatchDock server.

Determining the stoichiometry and binding constants of inclusion complexes formed between aromatic compounds and β-cyclodextrin by solid-phase microextraction coupled to high-performance liquid chromatography

The complexation of native β-cyclodextrin (CD) and seven aromatic compounds, namely, phenetole, toluene, m-xylene, naphthalene, biphenyl, fluorene and phenanthrene, has been studied for first time utilizing a solid-phase microextraction (SPME)–high-performance liquid chromatography (HPLC) method. The stoichiometries of the analyte:β-CD complexes were found to be either 1:1 or 1:2. The formation of 1:2 complexes was confirmed for naphthalene, biphenyl, fluorene, and phenanthrene only when utilizing relatively high concentrations of β-CD (up to 6.6 mM). The 1:2 stoichiometries were confirmed using the classical modified Benesi–Hildebrand (BH) method. The calculated binding constants for 1:1 stoichiometries ( K 1) using the SPME method varied from 115.3 M −1 for toluene to 3510 M −1 for phenanthrene, whereas the corresponding values to the 1:2 stoichiometries ( K 3) varied from 7.30 × 10 5 M −2 for biphenyl to 9.03 × 10 6 M −2 for naphthalene.

Binding constants of inclusion complexes of nitroimidazoles with β-cyclodextrins in the absence and presence of PVP

Thermodynamics of complexation of 5-nitroimidazoles with β-cyclodextrin and its methylated and hydroxypropyl derivatives in water and in 0.25% polyvinylpyrrolidone are determined by solution calorimetry. A 1:1 stoichiometry was established. The equilibrium constant ( K) for all the nitroimidazoles fall in the range 1000–1900 M −1 suitable for use of cyclodextrins as drug carriers. The complexation ability is significantly enhanced by methylation of the β-cyclodextrin. The stability constant increased in the order metronidazole < ornidazole < tinidazole < secnidazole. The presence of polyvinylpyrrolidone enhances the stability constants.

Substrate selectivity in byphasic Wacker-oxidation of alkenes in the presence of water-soluble calixarenes

Biphasic Wacker-oxidation of higher olefins, catalyzed by palladium complexes with water-soluble sulfonated calix[4]arene- and calix[6]arene-derived ligands have been studied. Complexes showed high catalytic activity under mild conditions and can be multiply reused. Catalysts display substrate selectivity in oxidation of C 6 and C 8 olefins—internal cavity of calixarenes recognizes the size of the substrates. The correlation between binding constants of inclusion complexes and selectivity has been established.

Biphasic Wacker-oxidation of 1-octene catalyzed by palladium complexes with modified β-cyclodextrins

New water-soluble palladium complexes with molecular recognition abilities based on β-cyclodextrin (β-CD) modified by nitrile-containing groups have been designed. Complexes display high catalytic activity and selectivity in two-phase Wacker-oxidation of 1-octene under mild conditions. The correlation between binding constants for inclusion complexes of β-CD-based compounds with substrate and the reaction rates has been established.

Binding constant dependency of amphetamines with various commercial methylated beta-cyclodextrins.

Cyclodextrins play an important role in enantioselective separations. They represent the major class of chiral selectors used by capillary electrophoresis. Unfortunately, the purity of commercial cyclodextrins is often not well characterized, and similar selectors sold by various suppliers may show totally different enantioselectivities. In this study, the composition of several commercial methylated-beta-cyclodextrins is evaluated by means of previously developed analytical methods. Then, different calculation methodologies, such as graphical determinations, as well as nonlinear or linear regression approaches, are evaluated in order to calculate the binding constants of inclusion complexes formed by some amphetamine derivatives with methylated-beta-cyclodextrins. The nonlinear curve-fitting methodology proves to be the most suitable for these determinations. Comparisons are made between the different selectors and several hypotheses are proposed concerning the formation of the inclusion complex. Finally, enantiomeric resolutions are evaluated for these selectors and conclusions drawn about the knowledge of selector composition.

Inclusion complex formation constants of α-, β-, γ-, δ-, ε-, ζ-, η- and θ-cyclodextrins determined with capillary zone electrophoresis

In contrast to the well known small cyclodextrins (CD), cyclomaltohexaose ( α-CD), cyclomaltoheptaose ( β-CD) and cyclomaltooctaose ( γ-CD), very limited information is available on larger CD and their inclusion complex forming properties. Using capillary electrophoresis, the binding constants of inclusion complexes formed with cyclomaltononaose ( δ-CD), cyclomaltodecaose ( ε-CD), cyclomaltoundecaose ( ζ-CD), cyclomaltododecaose ( η-CD) and cyclomaltotridecaose ( θ-CD) and various anions were determined and compared to the corresponding binding constants of α-, β- and γ-CD. All of the large CD were capable to form inclusion complexes. Dependent on the type of guest molecules, δ- and ε-CD were the weakest complex formers. The complex forming ability of ε, ζ-, η-, and θ-CD increased with increasing size of the ring structure and θ-CD displayed inclusion complex formation constants comparable to γ-CD.