Showing papers in "Journal of Inclusion Phenomena and Macrocyclic Chemistry in 1983"

A study of the NaxTiO2 system by electrochemical deintercalation

Abstract: The electrochemical deintercalation from the sheet oxide NaTiO2 leads to new Na x TiO2 materials. The deintercalation is reversible over the range 0.70≲x≤1, whereas irreversible modifications of the host structure occur by overvoltage (x≲0.70). This behavior, which can be explained by migration of some titanium ions from the slabs to the intersheet space, may be considered as a 2D→3D structural transition.

A proposal for the classification and nomenclature of host-guest-type compounds

Abstract: We suggest a system of classification and naming of general application to host-guest-type compounds. The classification is based on several criteria, including the host-guest type and the host-guest interaction, but also on topological and numerical considerations. The application of this concept to the classification of any host-guest situation is illustrated by several examples.

Dimethyl-β-cyclodextrin as parenteral drug carrier

Abstract: The following advantages are expected from the application of a soluble non-toxic inclusion-complexing drug carrier: (a) aqueous injectable solutions could be prepared from insoluble or poorly soluble drugs; (b) the stability of the dissolved drug could be improved; (c) by decelerating the elimination (by diffusion, circulation, metabolism) the duration of the biological effect could be prolonged; (d) by reducing the plasma, level of the active drug (=free, non-complexed drug) through complexation, the toxic effects could also be reduced; (e) in oral administration the bioavailability will be strongly enhanced.

Substrate binding to cyclodextrins in aqueous solution: A multicomponent self-diffusion study

Abstract: It is demonstrated that substrate binding to α- and β-cyclodextrins (CD) in solution can conveniently and directly be monitored from multicomponent self-diffusion data on these solutions, using the Fourier Transform NMR pulsed-gradient spin-echo technique. Included are aromatics and a series of alcohols ranging from methanol to octanol. Experimentally it was found thatn-alcohols associate more strongly with α-CD than with β-CD. As the bulkiness of the alcohol increased, binding to β-CD was enhanced while the reverse effect was observed in the case of α-CD. For both cyclodextrins it was found thatn-alcohol complexation in the homologous series was attributable to an increment in standard free energy of complexation of ∼ −3.0 kJ/mol for each −CH2− group, suggesting that the binding mechanism is of a hydrophobic nature.

Complexes of short-chain alcohols withβ-cyclodextrin

Abstract: The complex formation of β-cyclodextrin with short chain aliphatic alcohols has been studied. The stability constants of 1∶1 complexes, determined spectrophotometrically, increase monotonically in the series of normal alcohols, while branching in the chain results in a further increase in stability. With smaller monoalcohols, complexes containing more than one guest molecule are formed as well, but the relative stability of these complexes decreases with increasing chain length and branching. The stabilities of 1∶1 complexes decrease with an increasing number of OH-groups, probably due to a stronger hydration. This reflects both the roles of space filling and hydrogen bridging

Inclusion compounds —Past, present, and future

Abstract: 3.8. Future 24 Introduction 24 The Synthesis of Host Lattices with 'Tailor Made' Properties Studies of Guest Molecule Reactivity 27 Uses of Inclusion Compounds as Chemical Reagents 28 Media for Stabilizing Unstable Species 31 Biochemical and Industrial Applications 34 New Physical Techniques for Studying Inclusion Compounds 3.7.1. Magic Angle Spinning NMR Spectroscopy 36 3.7.2. High Resolution Electron Microscopy 38 3.7.3. Infrared and Raman Difference Spectroscopy 40 Applications of High Energy Particle Technology 41 25

(β-Cyclodextrin)2·KI7·9 H2O. Spatial fitting of a polyiodide chain to a given matrix

Abstract: α-Cyclodextrin, a torus shaped molecule with a 5 A wide central cavity, forms a number of deep green, blue and black crystals when complexed with iodine/metal iodide. In contrast, β-cyclodextrin, having a 6 A cavity produces only one type of reddish-brown crystal, no matter what metal iodide is used. The complex (β-cyclodextrin)2 ·KI7·9H2O displays space groupP21 (pseudo-C2) with cell constantsa=19.609(5),b=24.513(7),c=15.795(6)A, β=109.50(2)°,Z=4. The crystal structure was solved inC2 on the basis of 3022 absorption corrected CuKα (Ni-filter) X-ray intensities and refined by full matrix least squares toR=17%. This relatively highR-factor is due to many weak reflections (pseudo-C2) and considerable disorder exhibited by water and iodine. In the complex, β-cyclodextrin adopts a ‘round’ shape with O(2)...O(3) interglucose hydrogen bonds formed and all O(6) hydroxyls pointing away from the cavity. Two molecules are arranged head-to-head to produce a dimer, and dimers are stacked such that a slightly zigzagged cylinder with a 6 A-wide cavity is formed. In the cavity described by each dimer, an I 7 − ion composed of I2·I 3 − ·I2 units is located, with I2 and I 3 − perpendicular to each other. K+ ions and 9 H2O molecules are found in interstices between the β-cyclodextrin cylinders. This zigzag polyiodide contrasts with the linear form observed in the 5 A wide α-cyclodextrin channels. It explains differences in color of the crystals and suggests that β-cyclodextrin polyiodide is not a good model for blue starch-iodine.

Reaction of trimethylaluminum with crown ethers. II. The synthesis and crystal structure of (Dibenzo-18-crown-6)tris(trimethylaluminum) and of (18-crown-6)tetrakis(trimethylaluminum)

Abstract: Both title compounds were prepared by adding AlMe3 to a suspension of the appropriate crown ether in toluene, followed by reaction in a sealed tube. Both products were obtained in the form of extremely air-sensitive, colorless crystals. [AlMe3]3[dibenzo-18-crown-6] crystallizes in space group PĪ, witha=8.898(4),b=11.848(5),c=19.060(6) A, α=74.86(3), β=80.73(4), and γ=67.02(4)°. Refinement led to a final conventional weightedR value of 0.052 for 1800 reflections. [AlMe3]4[18-crown-6] belongs to space group Pbcn, witha=18.753(3),b=12.570(6), andc=15.095(6) A. Refinement was taken toR w =0.064 for 1320 reflections.

Chromatographic properties of s -triazines in the presence of soluble β-cyclodextrin polymer

Abstract: The effect of a water-soluble β-cyclodextrin polymer on the lipophilicity and adsorption strength of 17 substituteds-triazine derivatives was studied by thin-layer chromatography. Beta-cyclodextrin polymer dissolved in the mobile phase modifies the chromatographic behaviour ofs-triazine derivatives and, consequently, higherR f and lowerR M values were observed. LiCl exerts an opposite influence, it decreases theR f and increases theR M values. The β-cyclodextrin polymer enhances the mobility of thes-triazine derivatives on silica gel and reduces their lipophilicity, thus promoting their penetration through the hydrophilic membranes of the target organism. The presence of LiCl decreases the stability of inclusion complexes. The first and second substituents on thes-triazine ring result in an increase of the inclusion complex stability but — due to steric hindrances — the third substituent decreases it.

Zeolite inclusion complexes

Abstract: Zeolites provide the largest and most useful family of porous host crystals, stable in the presence or absence of guest molecules. An account is given of their structural characteristics in terms of intracrystalline channels and cavities of molecular dimensions; their total intracrystalline pore volumes; and the intracrystalline distribution patterns of guest molecules, often present as clusters or filaments. The way in which the shape and size of the molecules relate to the shape and size of the apertures or windows giving access to the cavities, together with other factors such as cation location, then determine molecule sieving behaviour, which is discussed with reference to several types of zeolite sieve. The relation between diffusivity and molecular dimensions is also illustrated. A comparison between zeolites and clathrate host lattices shows that there are strong similarities of several kinds. Zeolites may form inclusion complexes with metals, salts and polar or non-polar molecules, examples of which are briefly considered, together with isotherms for some of these types of complex. An account of equilibrium and its formulation demonstrates the thermodynamic background and illustrates the degree of success which has been obtained in describing isotherms in terms of various models.

The use of crown ethers to access new M[Al2R6X] species. Synthesis and crystal structure of [K · dibenzo-18-crown-6] [Al2Me6Cl] · 2 C6H6

Abstract: Potassium chloride does not react with trimethylaluminium in benzene in the absence of a crown ether. With the addition of dibenzo-18-crown-6, a normal liquid clathrate ensues. The composition of the parent compound has been established by a single crystal X-ray diffraction study. The space group is monoclinicP21/c with unit cell dimensionsa=21.319(8),b=9.512(4),c=21.081(8) A, β=93.79(3)°, andρcalc1.15 g cm−3 forZ=4. Refinement led to a final conventionalR value of 0.049 for 2224 observed reflections. The anion has the expected angular geometry (Al−Cl−Al=120.0(1)°). There are two different types of benzene in the crystalline solid. One is associated with the K+ ion, while the other exists in layers normal to thea axis.

CP/MAS13C NMR study of Dianin's compound [4-(p-hydroxyphenyl)-2,2,4-trimethylchroman]clathrates

Abstract: Solid-state13C NMR spectra are reported for Dianin's compound [4-(p-hydroxyphenyl)-2,2,4-trimethyl-chroman) and its clathrates with acetic acid, ethanol, acetonitrile and octanoic acid. Some of the methyl carbon chemical shifts depend on the presence of guest molecules and are also sensitive to guest size. Methyl13C spin-lattice relaxation times, reflecting the methyl reorientational barrier heights, are also extremely sensitive to guest size.

A silyl-α-cyclodextrin intermediate. Preparation and characterization of dodeca- t -butyldimethylsilyl-hexahydroxy-α-cyclodextrin

Abstract: The title compound (II) was prepared by treating dry, purified α-cyclodextrin with 20 equivalents oft-butyldimethylsilyl chloride 20 hr at 110° in DMF/pyridine. Work-up of the product mixture gave 60%II, which was identified by1H and13C NMR. Treatment ofII with Bu4NF 6 hr in refluxing dry THF efficiently removed the protecting groups.

Magic angle spinning29Si and27Al NMR study of mordenite dealumination

Abstract: Magic angle spinning29Si NMR presents a rapid qualitative method of assessing the degree of dealumination of sodium mordenite modified by acid leaching and heat treatment. A quantitative determination of the29Si coordination sphere is hampered by the overlap of chemical shift ranges for Si−O−Al and Si−O−H species. MAS27Al NMR indicates the presence of octahedrally coordinated Al in interstitial sites in all treated samples. On treating mordenite samples at high temperatures (∼700°C) much of the Al becomes invisible to the NMR experiment because of its location in sites of low symmetry and large quadrupole coupling constant.

Hydration reaction of Hofmann's benzene clathrate, diamminenickel(II) tetracyanonickelate(II)-benzene-(1/2), suspended in aqueous media

Abstract: Hofmann's benzene clathrate Ni(NH3)2Ni(CN)4·2C6H6 suspended in ammoniacal, neutral, and acidic aqueous media undergoes the replacement reactions of the guest C6H6 and the ligating NH3 molecules with molecules of water to give Ni(NH3)2Ni(CN)4·≅1H2O, Ni(H2O)2Ni(CN)4·nH2O(0

Crystal and molecular structure of a 1:1 complex of a chiral α-d-glucosido-benzo-18-crown-6 and potassium thiocyanate

Abstract: C28H36O10. KSCN is monoclinic, space groupP21 withZ=2,a=10.390(3),b=8.959(7),c=16.377(7) A, β=92.49(5)°. FinalR=0.053 for 1437 reflections measured at room temperature. The K– ion lies on the least-squares plane formed by the six oxygen atoms in the macrocyclic ring. The SCN− ion was found on the same face of the macrocycle as the chiral glucopyranoside moiety.

The structure of the 1,4-butanediol clathrate of a bis-ammonium salt of azulene

Abstract: The X-ray structure of the 1,4-butanediol clathrate ofN,N′-[1,3-azulenylenebis(methylene)]bis(trimethyl-ammonium)-diiodide is described, and the differences as well as the similarities to the 1-butanol inclusion of the same host are discussed in detail. The unit cell data of further clathrates of this new type are quoted.

Crystal structure analysis of the inclusion compound of 2′-hydroxy-2,4,4,7,4′-pentamethylflavan with 1,4-dioxan and water

Abstract: The 2: 1: 2 complex of 2′-hydroxy-2,4,4,7,4′-pentamethylflavan (1) with 1,4-dioxan and water is triclinic, space groupP\(\bar 1\), witha=8.164(1),b=8.960(1),c=14.644(1) A, α=91.56(1), β=97.19(1), γ=103.37(1)°; there are two flavan host, two water molecules and a single 1,4-dioxan guest molecule in the unit cell. The dioxan molecule is linked,via a hydrogen-bonded water molecule, to the phenolic OH group. The second hydrogen of this water molecule is also involved in hydrogen bonding, in this case to the ring oxygen of a second host molecule. Thus a hydrogen-bonded hexameric unit, a common feature of many clathrates of phenolic hosts, is not found in the present structure.