Formation Of Inclusion Compounds Research Articles

Use of halogen sensor groups for specific trapping of polyhaloalkanes

Multiple halogen ⋯ halogen interactions between the bromine atoms of 3 and polyhaloalkanes result in the formation of stable inclusion compounds, as illustrated here for the X-ray structure of 3·CHCl3, while other molecules of comparable size are excluded.

Helical tubulate inclusion compounds

Abstract The inclusion properties of the first helical tubuland diol hosts 1–5 have been surveyed and are reported. Bicyclic diol 1 forms helical tubulate inclusion compounds with most small solvent molecules, but with certain phenols hydrogen bonded co-crystalline materials are produced instead. Diol 2 yields helical tubulates with larger guest molecules, but if smaller solvents are used then an alternative host system is obtained. This has the guests trapped in ellipsoidal cavities located along constricted canals and is termed the ellipsoidal clathrate type. In some cases both inclusion types can be produced from 2 by varying the experimental conditions. The free volume present in the helical tubuland lattices of 3 and 5 is insufficient for guest inclusion. Diol 4 has the largest void space and can form inclusion compounds with large molecules such as ferrocene and squalene. X-ray crystal structures of representative examples of these compounds are discussed.

Properties and Structure of Aqueous Solutions of Hydroxypropyl‐beta‐Cyclodextrin

AbstractMolecules of hydroxypropyl‐beta‐cyclodextrin (HPBCD) in aqueous solution interact with each other via hydrogen bonds. Especially for concentrations beyond 50% (w/w), a strong increase in viscosity and a considerable decrease of freezable water can be determined. The addition of substances which are able to break the water structure (urea, KSCN) reduces these effects remarkably. The formation of inclusion compounds with urea could not be detected. Endothermic phase transformations confirm the presence of liquid crystalline structures at low temperatures. These liquid crystalline structures are not detectable at room temperatures, but the freeze fracture technique shows micelle‐like associates of a size of about 20 nm. Studies on the complexation of phenolphthalein as well as surface tension measurements of HPBCD solutions indicate that a minimum concentration of HPBC is necessary for the association phenomena.

35Cl nuclear quadrupole resonance and crystal structures of small guest molecules in tris(2,4-pentanedionate)M(III) inclusion compounds

Tris(acetylacetonate)M(III) complexes, where M = AI, V, Cr, Mn, Fe, Co and Ga, form inclusion compounds with different solvent molecules. The compounds have a host/guest ratio of 1:2 for the small guest molecules CHCl 3 and CH 2Cl 2 and of 1:1 for the slightly bigger guest molecules trans-CHClCHCl, CH 2ClCH 2Cl and CCl 4. The 35Cl nuclear quadrupole resonance spectra of these clathrates have been measured in the temperature range 4–200 K. The site symmetry, the existence of different crystal phases, the molecular disorder and molecular motions of the guest molecules in the host cavities, and the host-guest interactions, were evaluated from the NQR frequency measurements. The crystal structures of the M(AcAc) 3/ trans-CHClCHCl compounds were measured at room temperature and confirm the NQR results.

Composition and properties of freeze-dried products of nicotinic acid with?-cyclodextrin and heptakis (2,6-0-dimethyl)-?-cyclodextrin

The purpose of the study was to examine the formation of inclusion compounds in the freeze-dried products obtained from aqueous solutions of nicotinic acid and β-cyclodextrin (β-CD), or heptakis (2,6-0-dimethyl)-β-cyclodextrin (DIMEB). The molar ratios used were 1:1 and 2:1. In addition two freezing temperatures (−40 and −196°C) and different secondary drying temperatures (+50 and +80°C) were used. Freeze-dried products with β-CD obtained after low temperature freezing are of the same crystallographic structure as seen in a pure inclusion compound prepared by coprecipitation. Amorphous products were formed after fast freezing. The molar ratios of included nicotinic acid in the freeze-dried products vary — dependent on the preparation conditions — between 0.75:1 and 1:1. A factorial design proves that the included drug amount can be increased by enhancement of the amount of nicotinic acid used, by faster freezing, and by the combination of these two factors. The proof of inclusion formation was given by a combination of X-ray diffractography, differential scanning calorimetry, thermogravimetry and thermofractography.

Complexation with diol host compounds: Part 9. Structures and thermal analyses of inclusion compounds of trans-9,10-dihydroxy-9,10-diphenyl-9,10- dihydroanthracene with acetonitrile and 3-hydroxypropionitrile

The host compound ( H), trans-9,10-dihydroxy-9,10-diphenyl-9,10-dihydroanthracene forms inclusion compounds with acetonitrile (compound 1) and 3-hydroxypropionitrile (compound 2) both with host : guest ratio of 1:2. Crystal data: ( 1) C 26H 20O 2·2C 2H 3N, M r = 446.54, a = 8.530(2), b = 16.995(6), c = 9.034(1) Å, β = 109.15(2)°, space group P2 1/c , D m = 1.18 g cm −3, D c = 1.20 g cm −3 for Z = 2, R = 0.096 for 1363 reflections; ( 2) C 26H 20O 2·2C 3H 5NO, M r = 506.60, a = 8.444(1), b = 9.7931(7), c = 16.558(2) Å, β = 104.32(1)°, space group P2 1nD m = 1.28 g cm −3, D c = 1-27 g cm −3 for Z = 2, R = 0.066 for 1567 reflections. The thermal decomposition of (1) shows that the guest release reaction occurs in a single step, but that the activation energy varies with the extent of decomposition, from 83 to 114 kJ mol −1. DSC of ( 2) shows that decomposition is more complex, with possible phase changes of the host structure.

Approaches to gradient elution in ion-exclusion chromatography of carboxylic acids

A range of eluents has been examined with a view to determining which can be used to manipulate the selectivity of retention in ion-exclusion chromatography when applied to the separation of common water-soluble carboxylic acids. The column used was a Bio-Rad HPX-87H Organic Acids column and the eluents examined included water and dilute solutions of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, methanesulfonic acid and benzoic acid. Both conductivity and ultraviolet detection were utilized. The use of water alone as an eluent gave poorly shaped peaks, whilst the remaining eluents gave satisfactory peak shape. The best performance was obtained using methanesulfonic acid as eluent. Studies on gradient elution in ion-exclusion chromatography were also undertaken. Three approaches to gradient separation were investigated. The first approach was to utilize a concentration gradient in which the eluent concentration was decreased over the run, thereby increasing the degree of solute ionization and thus solute retention times. This method proved to be of limited utility. The second approach involved increasing the amount of an organic modifier (acetonitrile) in the eluent, and satisfactory gradients were produced by this method. In the third approach, a varying concentration of -cyclodextrin was introduced into the eluent as a means of reducing the retention times of aromatic solutes through the formation of inclusion compounds with -cyclodextrin. Once again, satisfactory gradient separations were produced with this approach.

Stabilization of dyes against hydrolytic decomposition by the formation of inclusion compounds

The decomposition reactions of the dyes phenol blue and murexide were measured spectroscopically in acidic solution at different temperatures. From these reaction rates and their temperature dependence in the absence and presence of various hosts, the stability constants and the reaction enthalpies of the dye complexes with noncyclic dextrins, cyclodextrins and cucurbituril were calculated.β-Cyclodextrin enhances the stability of phenol blue in acidic solution. This effect is even more pronounced with cucurbituril. Due to the molecular structure of murexide this dye cannot form inclusion complexes with hosts containing hydrophobic cavities.

Stereochemistry and transformation of -OH…O= hydrogen bonds Part I. Polymorphism and phase transition of 1,3-cyclohexanedione crystals

The properties of substances or crystals which may depend on the stereochemical configuration of bistable -OH…O= hydrogen bonds are analysed for 1,3-cyclohexanedione crystals and compared with other simple cyclic β-diketoalkane structures (enolized forms). 1,3-Cyclohexanedione (CHD) is known to form monoclinic crystals, space group P2 1/ c, built up of chains of hydrogen-bonden enol molecules (polymorph CHD1). When cooled to below 287(1) K or subjected to elevated pressures of about 10 MPa, the CHD1 crystal undergoes a phase transition involving an H-atom transfer in the hydrogen bond (structure CHD2). The mechanism of this hydrogen-bond transformation is explained. A new polymorph of 1,3-cyclohexanedione (CHD3) is reported and its structure has been dete The CHD3 cyrstals are monoclinic, space group P2 1, with two different stereochemical configurations of the hydrogen bonds. The CHD structures, as well as other simple cyclic β-diketoalkanes and squaric acid, illustrate the interdependence between the stereochemical configuration of bistable -OH…O= hydrogen bonds and the crystal structure, polymorphism, formation of inclusion compounds, phase transitions and other structural transformations, which affect the physical properties of the crystals.

Preparation and properties of inclusion compounds of cobalt cluster complexes with γ-cyclodextrin

Inclusion compounds of di-, tri-, and tetranuclear transition metal complexes with γ-cyclodextrin (CD) have been prepared as the first example of an inclusion compound of cyclodextrin with a metal cluster complex. High yields of crystalline one-to-one inclusion compounds were obtained by the treatment of η 2-acetylenedicobalt hexacarbonyl complexes with γ-CD. μ 3-Phenylmethylidynetricobalt nonacarbonyl, and η 6-mesitylenetetracobalt nonacarbonyl also form inclusion compounds with γ-CD. The formation of inclusion compounds is selective. γ-CD forms 1 : 1 host : guest inclusion compounds with η 2-phenylacetylene- and η 2-phenylmethylacetylenedicobalt hexacarbonyls, but not with the sterically larger η 2-diphenyldicobalt hexacarbonyl. Neither α-CD nor β-CD formed inclusion compounds with any of the cobalt cluster complexes tested. The metal cluster complexes included in γ-CD are thermally more stable than the free complexes.

Threading Cyclodextrin Rings on Polymer Chains

Another form of molecular self-assembly—the threading and unthreading of ring-shaped molecules on a polymer chain (represented schematically here) was studied by NMR spectroscopy and followed qualitatively for the formation of polymeric inclusion compounds made up of cyclodextrins and poly-(iminooligomethylene)s. The structures of the polymeric inclusion compounds are proven by their conversion to polyrotaxanes.

Inclusion of azoniabetain dyes by cyclodextrins.

Formation of inclusion compounds between azoniabetain dyes (2-styryl benzo [a] quinoliziniums, A, B and C) and α-, β- and γ-cyclodextrins (CD) has been investigated from the absorption spectra accompanied by negative solvatochromism. As reference, 4-nitrophenol, potassium 4-nitrophenolate and 4-nitroaniline were used as indicator of the inclusion. The latter three compounds formed inclusion compounds only with α-CD, but not with β- and γ-CD's because of their larger cavity radii. Dye A in OH 0-forms was not included by the three CD's by the steric hindrance of oxygen at o-position of the dye. Dyes, B and C in OH form were not included by α-CD but formed 1:1 inclusion compounds with β- and γ-CD's, and in 0- form, they formed 1:1 incusion compounds with the three CD's. The formation constants were found to be in the order; β-CD > γ-CD > α-CD. Structures of the inclusion compounds were suggested based on their spectra.

シクロデキストリン固体分散系中での医薬品分子状態の研究

Molecular states of drug molecules in cyclodextrin solid dispersion systems have been studied. The possibility of inclusion compound formation was investigated between drug and cyclodextrin molecules by grinding, sealed heating and freeze drying. Solid state fluorescent spectroscopic measurements were made on the ground mixtures as well as infrared and photo-acoustic spectroscopies. It was found that time resolved solid state fluorescence analysis was effective to investigate the molecular states of fluorescent probe dispersed in cyclodextrins. Sealed heating of drug-cyclodextrin mixture was recognized as a new unique method for preparing cyclodextrin inclusion compound. In the case of freeze drying, the freezing conditions showed great influences on the drug dispersion states and the crystallinity of the products. The results are explained in terms of the inclusion compound formation by grinding, sealed heating and freeze drying.

Diastereomer Separation by Formation of Inclusion Compounds: 2,6‐Dimethylnaphthalene Complexes of Flumethrin

Diastereomer Separation by Formation of Inclusion Compounds: 2,6‐Dimethylnaphthalene Complexes of Flumethrin

Inclusion complexes between β‐cyclodextrin and β‐benzyloxy‐α‐propionic derivatives of paramagnetic DOTA‐ and DPTA‐Gd(III) complexes

AbstractThe addition of β‐cyclodextrin to a solution containing β‐benzyloxy‐α‐propionic‐substituted DOTA‐ and DTPA‐Gd(III) complexes leads to the formation of inclusion compounds whose equilibrium constants have been determined by NMR titrations. The main effect associated with the formation of this ‘host‐uest’ interaction is a marked elongation of the molecular reorientational time, τr, which in turn results in increased solvent proton relaxation rates.

Double‐Diamond Inclusion Compounds of 2,6‐Dimethylydeneadamantane‐1,3,5,7‐tetracarboxylic Acid

AbstractThe crystal structures of four inclusion compounds of 2,6‐dimethylideneadamantane‐1,3,5,7‐tetracarboxylic acid (4) are described, which involve the following guest species: (a) a mixture of 4‐methylpent‐3‐en‐2‐one, 2,6‐dimethylhepta‐2,5‐dien‐4‐one, and mesitylene (condensation products of acetone); (b) mesitylene; (c) a mixture of 4‐methylpent‐3‐en‐2‐one and mesitylene; (d) (tert‐butyl)benzene. In all four cases, the host architectures consist of two interpenetrating super‐diamond networks built up by the tetra‐acid molecules via pairwise H‐bonds between the tetrahedrally directed COOH groups. In the first three cases (tetragonal crystal symmetry), the two diamond‐like host lattices interpenetrate symmetrically, in the fourth case (monoclinic) asymmetrically. This asymmetry is brought about by the increased steric bulk of the (tert‐butyl)benzene guest molecules. Attempts to enforce an inclusion compound of 4 with a single, extremely hollow diamond‐like host lattice by offering still bulkier guest molecules have as yet not been met with success. The generally very high propensity of 4 to form inclusion compounds was envisaged and designed beforehand by appropriate evaluation and modulation of the crystal structure of the parent adamantane‐1,3,5,7‐tetracarboxylic acid, which represents a fivefold diamond‐like self‐inclusion compound. Crystals of the free, uncomplexed 4 appear to be extremely unstable and could so far not be obtained. On the other hand, from aqueous solution a very stable monohydrate of 4 may be crystallized (4‐H2O), which was also subjected to X‐ray analysis. The (triclinic) crystal structure of 4·H2O involves an interesting dichotomy inasmuch its pattern of H‐bonding may be rationalized either in terms of a double, cross‐linked super‐zincblende (sphalerite) architecture, or as a system of porous, puckered 4‐connected sheets, which interpenetrate each other pairwise and are cross‐linked by the H2O molecules. Various structure and (space group) symmetry characteristics of the supramolecular solid‐state complexes reported here are highlighted by pointing out analogies with comparable structures retrieved from the literature.

Complexation with diol host compounds. Part 6. Structure and dynamics of enclathration by 1,1,6,6-tetraphenyl-hexa-2,4-diyne-1,6-diol

The host compound 1,1,6,6-tetraphenyl-hexa-2,4-diyne-1,6-diol forms inclusion compounds with acetone( Pbca) and benzophenone( P2 1 c ). The structures of the nonporous α-phase of the host ( P1 bar), as well as those of the host-guest compounds, have been elucidated. The kinetics of the reaction of the host with both these guest molecules have been analyzed.

1H NMR spectroscopy as a probe of intermolecular interactions in ?-cyclodextrin inclusion compounds

1H NMR spectroscopy was used to probe the formation of inclusion compounds of permethylated and peracetylated s-cyclodextrins as host molecules and a variety of electronically very different guest molecules. Complexation, obtained only in water, was estimated quantitatively by means of chemical shift/concentration curves of relevant protons, and the intermolecular forces involved are criticially discussed.

New Methods for Preparing Cyclodextrin Inclusion Compounds. IV. Enhancement of Combining Molar Ratio by Using a Ground Mixture in Heptakis-(2,6-di-O-methyl)-.BETA.-cyclodextrin and Benzoic Acid System.

The inclusion compound of heptakis-(2, 6-di-O-methyl)-β-cyclodextrin (DMβCD) with benzoic acid was prepared by heating the ground mixture in a sealed container. The formation of teh inclusion compound was investigated quantitatively as a functions of heating temperature, heating time, and grinding time. Differential scanning calorimetry (DSC) measurements were made of the ground mixture at different grinding times. From teh DSC measurements, it was found that the temperature of crystallization of an amorphous ground mixture increased with an increase in grinding time. When the ground mixture was heated in a sealed container, the combining molar ratio of benzoic acid to DMβCD increased as the heating temperature increased. The experimental results indicated that the inclusion compound was obtained more effectively by heating the ground mixture rather than by heating the physical mixture.

Selective Reactions in Crystalline Inclusion Compounds

Abstract 1,1,6,6-Tetraphenylhexa-2,4-dyine-1,6-diol and it's chiral derivative 1,6-bis(o-chlorophenyl)-1,6-diphenyl-2,4-dyine-1,6-diol form inclusion compounds with various potentially reactive guest molecules. Photochemical reactions of a-oxoamides imbedded within the matrix of the host molecules afforded in stereo and enantiospecific B-lactam derivatives. Similar reactions with α-tropolone alkyl ether reveal, in 100% e.e. (enantiomeric excess), a bicyclic product. Over 40% e.e. of phenylalcohols were obtained by solid state reduction of the corresponding phenylketones as the guest molecules.