Study of the Inclusion Complexes of β-Cyclodextrin with the Sodium Salt of Trisulfonated Triphenylphosphine

The formation of inclusion complexesbetween the sodium salt of trisulfonatedtriphenylphosphine and -cyclodextrin has beeninvestigated at two temperatures by high field nuclearmagnetic resonance, electrospray mass and UV-visspectroscopies. At 268 K, titration experiments andJob's method suggest that the major species insolution is a 1 : 1 inclusion complex. The moleculargeometry of this inclusion complex was studied usingthe ROESY NMR technique complemented by molecularmodelling. All these methods converged towards thestructure attained by inserting one aromatic ring intothe hydrophobic cavity of the host from the side ofthe secondary hydroxyls. At 298 K, a higher proportionof 2 : 1 and 3 : 1 complexes induces strong alterations ofthe NMR signals, preventing an easy and reliabledetermination of association constants. Nevertheless,an apparent association constant can be determinedfrom UV-vis data by assuming a 1 : 1 equilibrium. Thegeometry of the 2 : 1 and 3 : 1 complexes is also brieflydiscussed from ROESY NMR experiments.     

Complexation of the Non-steroidal Anti-inflammatory Drug Loxoprofen with Modified and Unmodified β-Cyclodextrins

The inclusion complex of the anti-inflammatory drug, loxoprofen, with -cyclodextrin-(CD), sulfated -CD, and glycerol ether -CD was studied by UV-VIS absorption and ¹H-NMR spectroscopy in solution. The inclusion complex of loxoprofen with -CDs was prepared by freeze-drying, and then characterized in the solid state by thermal analysis, X-ray diffraction, FT-IR and FT-Raman spectroscopy, and scanning electron microscopy (SEM). Furthermore, a physical mixture of loxoprofen/-CD (1/1, mol-%) in the solid state was also characterized. The solubility of the loxoprofen increased on addition of -CDs. The solubility enhancement of the loxoprofen with -CDs is in the following order: glycerol ether -CD > sulfated -CD > -CD.     

Bi-directional Inclusion Complexation of Methylalkyl Viologens with β-Cyclodextrin and Naphthyl group-Tethered β-Cyclodextrins

Inclusion complexation of methylalkyl viologens(C₁C_nV²⁺; n = 7–10, 12) withmono-6-O-(2-sulfonato-6-naphthyl)-β-CD (1)and mono-6-O-(2-naphthyl)-β-CD (2) werestudied by steady-state and time-resolved fluorescencespectroscopies and compared with the binding of theviologens with native β-CD investigated by induced circulardichroism. The viologens form bimodal complexes with1 and 2, in which the bipyridinium group of theviologens is placed on the primary side (type I complex) andsecondary side (type II complex) of β-CD cavity, while thegroup is predominantly on the secondary side in complexeswith native β-CD. The microscopic binding constantsK_I and K _II were calculated from theanalysis of fluorescence data. The formation of the type Icomplexes with 1 and 2 appears to be largely dueto the charge–transfer interaction between the bipyridinium andnaphthyl groups in the complexes. This work shows thatthe location of the bipyridinium group in β-CDcomplexes and in the type II complexes of the viologens with1 and 2 depends little on the length of alkyl chainof the viologens.     

Studies on Inclusion Complexes of Felodipine with β-Cyclodextrin

The inclusion behaviour of -cyclodextrin(-CD) with felodipine (FL) as a guest moleculewas studied. Inclusion complexes were obtained by thekneading method in a binary or ternary system with anaddition of polyethylene glycol 6000. Formation ofinclusion complexes was studied by IR spectroscopy,differential scanning calorimetry (DSC), and¹³C-NMR. It has been shown that an aromaticphenyl ring was involved in the process ofcomplexation, and that in the solid clathrates thesolubility of FL increased two fold when compared tothe physical mixture, while it increased 10 fold inliquid three-component complexes. Moreover, thephotochemical stability of felodipine was studied inits crystalline form and in the inclusion complexeswith -CD. Quantitative assessment of thefelodipine photochemical decomposition was made on thebasis of the rate constants of decomposition (k) inthe first order kinetic reaction, half life time(t_0.5) and the time of decomposition of 10% of thecompound (t_0.1). It was shown that complexationof FL with -CD causes a two fold increase ofthe rate of the photodegradation process.     

Experimental and Theoretical Studies on the Inclusion Complexation of β-Cyclodextrin with Phenothiazine Derivatives

Inclusion complexation of -cyclodextrin (-CD) with N-phenylphenothiazine ( 1), N-benzylphenothiazine ( 2) and N-phenethylphenothiazine ( 3) has been studied by means of UV-vis spectroscopy and molecular dynamics simulations. The association constants (K_a) were determined to be 126, 312 and 211 dm³/mol for inclusion of -CD with 1, 2 and 3, respectively. It shows that the K_a values are affected by the substituents of the guest compounds. The structures of the complexes and the conformation of the guest compounds bound by -CD in the complex have been discussed.     

Molecular Recognition Study on a Supramolecular System. Part 21. Inclusion Complexation Thermodynamics of Aliphatic Alcohols by Organoselenium Modified β-Cyclodextrins

The spectrophotometric titrations have beenperformed at 25–40 °C in aqueous solution to give the complexstability constants and the thermodynamic parametersfor the stoichiometric 1 : 1 inclusion complexation ofvarious aliphatic alcohols withmono[6-(phenylseleno)-6-deoxy]--cyclodextrin (2),mono[6-(o-, m-,p-tolylseleno)-6-deoxy]--cyclodextrin (3–5),mono[6-(p-chloro-phenyl-seleno)-6-deoxy]--cyclodextrin(6), mono[6-(benzylseleno)-6-deoxy]--cyclodextrin (7) and mono[6-(naphthaleneseleno)-6-deoxy]--cyclodextrin(8). On thebasis of the present and previous results, themolecular binding abilities and selectivities forguest aliphatic alcohols of the host -cyclodextrinderivatives (2–8) are discussed comparatively and globallyfrom the thermodynamic point of view. Thethermodynamic parameters obtained are criticalfunctions of the size/shape of aliphatic alcohols, andthe position and type of the substituent introduced tothe aromatic ring of -cyclodextrin's sidearm,which are elucidatedin terms of the conformational, electrostatic,hydrogen-bonding, and hydrophobic effects.     

Effects of Modified β-Cyclodextrins on the Hydrolysis Reaction of p-Nitrophenyl α-Methoxyphenylacetate

Effects of -cyclodextrin (-CD) 1and its derivatives 2–7 on the deacylationreaction of p-nitrophenyl (R or S)--methoxyphenylacetatewere studied. The-CD derivatives used were6--D-glucosyl--CD 2, sulfated-CD (7–11 sulfate groups/CD ring) 3,dimethylated -CD 4, carboxymethylated-CD (3.5 carboxymethyl groups/CD ring) 5,2-tri(2-hydroxypropyl)--CD 6, and-CD appended on poly(allylamine) 7. Therate constant (k ^CD) of thesubstrate/-CD complexes and the formationconstants (K) of the complexes were determinedfrom the dependence of the pseudo-first order rateconstants of the deacylation reaction on theconcentration of -CDs. The order ofk ^CD for the R-enantiomer at pH8.0 is 45H₂O3 6 1 2 7, whilethat for the S-enantiomer is 4 5 6H₂O 1 2 3 7: H₂O denotes the rate in theabsence of -CDs. The order of K values is3 7 6 2 1 4 5. This work indicates that, though thesecondary hydroxyl groups of -CD play criticalroles in the deacylation reactions of the esterscomplexed with -CDs, the reactivity of theester/-CD complexes depends highly on thenature of the substituents at the secondary face of-CD. It also suggests that the substratesinserted from the secondary side as well as theprimary side of -CD of poly(allylamine)-bound-CD undergo the reaction by attack of aminogroups on the polymer chain.     

Comparative Study on the Inclusion Complexation of Rutin with Cyclodextrin Supramolecules

Naturalandchemicallymodifiedcyclodextrinshaveabilitytorecogformanyinorgan-..icororganlcguestmoleculesfOrminghost-guestinclusioncomplexest13.Inrecentyears,increasingattentionhasbeenpaidtoalterphisical,chemicalandbiologicalpropertiesofmolecules'-Theunderstanding'ofthebehaviorofthedrugincyclodextrionmicroenwton-mentisaprerequisitetodevelopmentofanovelandeffectivecarrierspptemforthedrug.6-CDcanforminclusioncomplexeswithrutin[2J.WereporthereastudyoninclusioncomplexationofcyClodextrinsbyfluorAnetr…     

NMR Study of the Inclusion Complexes of Carboxy-Phenoxathiin Derivatives with β-Cyclodextrin

The inclusion complexes of the carboxylate forms of 3-carboxy-(I) and 2-carboxy-phenoxathiin (II) with -cyclodextrin were studied by bothone- and two-dimensional NMR spectroscopy. The analysis of the induced chemical shifts of theguests in the presence of different amounts of the host indicates the formation of complexes with 1:1stoichiometry and association averaged pK values of 3.75 (I) and 4.4 (II). Thequalitative analysis of cross peaks in the ROESY spectra support the inclusion of the guests in the cavitywith the substituted phenyl ring, the COO^- group being in the proximity of the primary rim.     

Correlation between Thermodynamic Behavior and Structure in the Complexation of Modified β-Cyclodextrins and Bile Salts

Complex stability constants (K _S), standard molar enthalpy changes (ΔH ⁰) and entropy changes (ΔS ⁰) for the inclusion complexation of two cyclodextrin dimers, 6,6′-{2,2′-diselenobis[2-(benzoylamino)ethylamino]}-bridged bis(β-cyclodextrin) (1) and o-phenylenediseleno bridged bis(β-cyclodextrin)s (3), and their monomer analogs, 6-deoxy-6-{[2-(2,3-dihydro-3-oxo-1,2-benzisoselenazol-2-yl)ethyl]amino}-β-cyclodextrin (2) and mono[6-(phenylseleno)-6-deoxy]-β-cyclodextrin (4), with two bile salt guests, sodium cholate (CA) and sodium deoxycholate (DCA), were determined at 25°C in Tris buffer solutions (pH 7.4) at 298.15?K by means of isothermal titration microcalorimetry (ITC). The interactions and binding modes between the host cyclodextrins and the guest bile salts were further studied by ROESY spectroscopy. The thermodynamic parameters obtained, together with the ROESY spectra, were used to examine the correlations between thermodynamic behavior and binding modes of the host–guest complexation. The results indicate that the length, structure and conformation of the tethers linked to the cyclodextrins determine the binding modes and the binding abilities between hosts and guests to a great extent, leading to a reversion in binding ability when comparing the corresponding dimer and its monomer analog.     

Effect of Temperature-responsive Solution Behavior of PNIPAM-bPPEOMA-b-PNIPAM on Its Inclusion Complexation with α-Cyclodextrin

The effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with α-cyclodextrin was studied. The triblock polymer was prepared by reversible addition-fragmentation chain transfer(RAFT) polymerization and formed inclusion complexes(ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of α-CD units. For comparison, PPEOMA homopolymer was prepared and the inclusion complexation with α-CD was also studied. The ICs were prepared with α-CD when the polymer was in different conformations by changing the temperature, and the formed ICs were characterized by XRD, 1H-NMR, TGA and DSC. The solutions of the ICs show temperature-responsive clear/turbid transition or fluidic emulsion/gel transition depending on the concentration of the α-CD added, and the stoichiometry determined by 1H-NMR and TGA indicates that the stoichiometry of EO to α-CD of the resulted ICs increases with increasing of temperature.     

Influence of Substituents in β-Cyclodextrin on the Interaction of Levofloxacin–β-Cyclodextrin Complexes with Liposomal Membrane

Colloid Journal - The effect of substituents (polar CH2CH(OH)CH3, hydrophobic CH3, and charged $${{\left( {{\text{C}}{{{\text{H}}}_{{\text{2}}}}} \right)}_{{\text{4}}}}{\text{SO}}_{3}^{ - }$$ ) in...     

Inclusion Complexation of β-CD with Phenothiazine and N-Alkylphenothiazine Derivatives

Phenothiazinederivatives(PTZ)havebeenstudiedfOrdecadesbecauseoftheirwideapplicationsintranquilizingdrugs,dyestuffsandsolarenergyconversionmaterialsI.Recently,westudiedtheelectrontransferreactionsofNsubstilutedphenothiazinewithelectronacceptorsinAcyclodextrin(ffCD)aqueous,olution2'3.TheelectrontransferprocesswassignificantlyinfluencedbythepresenceofffCD.IthasbeennotedthatthePTZwereincludedbyACDtoforminclusioncomplexes.Inthisletter,wereportthestudyofinclusioncomplexationofffCDwithphenoth…     

Effect of the Formation of Inclusion Complexes With β-Cyclodextrin on the Photoisomerization and Fluorescence Properties of Aromatic Norbornadiene Derivatives

The valence photoisomerization of four aromatic norbornadiene (NBD)derivatives has been studied in ethanol and in 0.01 M -cyclodextrin(-CD) water–ethanol (v/v, 99/1) solution (WECD). Observedfirst-order rate constants are found to be of the same order of magnitude inethanol and WECD, ranging between 0.1 and 0.28 s^-1, accordingto the compound. These photoisomerization kinetic properties are attributedto the formation of inclusion complexes between NBDs and -CD. Thestoichiometry is 1 : 1, and association constants ranging between 310 and390 M^-1 have been determined fluorimetrically, usingBenesi–Hildebrand plots and a nonlinear regression method. Thestructure of the inclusion complexes is discussed on the basis of AMIsemiempirical dimension calculations and photophysical properties.     

Retention of Cyclodextrins under the Conditions of Reversed-Phase Chromatography and Determining the Stability Constants of Inclusion Complexes of Antocyanins with β-Cyclodextrein

Russian Journal of Physical Chemistry A - The chromatographic behavior of α, β, and γ-cyclodextrins on three types of reversed-phase chromatography of stationary...     

Characteristic Studies of Arylated β-Cyclodextrins in Host-Guest Complexation with Small Molecules

Tornsshapedcyclodextrins(CDs,includingQ-,6-,y-CDetc.),whicharehydrophilicoutsideandhydrophobicinside,havegainedprominenceinrecentyearsforprovidingidealstoconstrUctefficientwtificialenZymes,molecularrecognitionsensorsandotherfunctionalmodelsl-3.ForbuildingmoreefficientartificialenZymesandmolecularrecognitionsensors'-',wehavepreparedaseriesof6-CDderivativesbearingchromophores'-',includingmono-2-O-benzoyI-9-CD(V),mono-3-O-benzoyl-0-CD(VI)andmono-6-O-benzoyl-0-CD(Vll)(Fig.l)andfoundthat3'…     

Stability of Ibuprofen in its Inclusion Complex with β-Cyclodextrin

The ibuprofen--cyclodextrin inclusion complex was prepared by theco-precipitation method. The identity of the obtained product was verified by X-ray and thermogravimetric techniques. The effect of -cyclodextrin on the stability of ibuprofen was analysed.     

Changes in the Solubility of β-Cyclodextrin on Complex Formation: Guest Enforced Solubility of β-Cyclodextrin Inclusion Complexes

The most common native host molecule, -cyclodextrin (cycloheptaamylose) is able toform inclusion complexes with a large variety of guestmolecules (or ions) of different size and shape. Theproperties of the included guest molecule are highlyinfluenced by the host-guest interaction, and thepractical usefulness of -cyclodextrin isdependent on these effects. These changes are mainlyinvestigated from the point of view of the guest andto a lesser extent from that of the host. In spite ofthis, the kind of guests and that of the host-guestinteractions during the formation of the inclusioncomplex seem to influence the properties of thehydrophilic domain of -cyclodextrin (i.e. thatof the supramolecule itself), too, and this effect canbe well demonstrated by the change of solubility ofdifferent -cyclodextrin inclusion complexes.This change can be best correlated with the solubilityof the guest as if the guest enforced its solubilityon the supramolecule.     

Thermodynamic and 13C NMR Studies of the Inclusion Complexes of α- and β-Cyclodextrins with Cyano- and Nitrophenols in Aqueous Solution

Equilibrium constants for the formation of 1 : 1 inclusioncomplexes of -cyclodextrin (-CD) with neutral and anionic phenol derivatives (3- and 4-cyanophenols and 3- and 4-nitrophenols) have been evaluated at 5, 12, 25, and 35 °C by means of spectrophotometry. Similarly, the equilibrium constants have been determined for the inclusion complexes of-cyclodextrin (-CD) with the phenols. Enthalpy and entropy changes for the formationof the inclusion complexes have been estimated from the temperature dependences of theequilibrium constants. With -CD, the enthalpy andentropy changes for the anionic species have been found to be more negative than those for the neutral ones, except for 4-cyanophenol, suggesting that the inclusion complexes of the anionic species are more rigid than those of the neutral species. From analyses of chemical shift differences in ¹³C NMR spectra of 3- and 4-cyanophenolsand 3- and 4-nitrophenols in aqueous solutions with and without CDs, a nitro ora cyano group has been found to be first bound to the - and -CD cavities.     

Theoretical Study of the Inclusion Processes of Ibuprofen Enantiomers with Native and Modified β-CDs

PM3 calculations in vacuum were performedon the inclusion complexation of-cyclodextrin (-CD),heptakis-(2-O-methyl)--cyclodextrin(2-Me--CD) and heptakis-(6-O-methyl)--cyclodextrin(6-Me--CD) withibuprofen (IB) enantiomers. Inclusion processpathways are described and the most probablestructure of the 1:1 complex are sought througha potential energy scan. The energy differencesbetween the inclusion complexes and the hosts(native and modified CDs) by calculation show thatmodified CDs have much more interaction sites withIB and enhance van der Waals interaction andhydrophobic interaction between them, form morestable complexes than native CD does.Stabilization energies of S-IB complexes arehigher than that of R-IB complexes both for nativeand modified CDs.