Oxygenation of alkenes with t-BuOOH catalysed by beta-cyclodextrin borate

beta-Cyclodextrin borate catalyses oxygenation of aryl substituted alkenes in the presence of t-BuOOH to afford beta-dioxy alcohols in good yields (63-86%). Copyright (C) 1996 Published by Elsevier Science Ltd

Headspace solid-phase microextraction with novel sol-gel permethylated-beta-cyclodextrin/hydroxyl-termination silicone oil fiber for determination of polybrominated diphenyl ethers by gas chromatography-mass spectrometry in soil

A simple, sensitive, and accurate method for determination of polybrominated diphenyl ethers (PBDEs) in soil has been developed based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). Permethylated-beta-cyclodextrin/hydroxyl-termination silicone oil (PM-beta-CD/OH-TSO) fiber was first prepared by sol-gel technology and employed in SPME procedure. By exploiting the superiorities of sot-gel coating technique and the advantages of the high hydrophobic doughnut-shaped cavity of PM-beta-CD, the novel fiber showed desirable operational stability and extraction ability. After optimization on extraction conditions like water addition, extraction temperature, extraction time, salts effect, and solvents addition, the method was validated in soil samples, achieving good linearity (r>0.999), precision (R.S.D. < 10%), accuracy (recovery>78%), and detection limits (S/N =3) raging from 13.0 to 78.3 pg/g. (c) 2007 Published by Elsevier B.V.

Water solubility enhancement of phthalates by cetyltrimethylammonium bromide and beta-cyclodextrin

Water solubility enhancements of six phthalates (five aliphatic phthalates and one phenyl phthalate) by cetyltrimethylammonium bromide (CTAB) and beta-cyclodextrin (beta-CD) were studied at 25 degreesC. The solubilities of these plithalates are remarkably enhanced by CTAB solutions above the critical micelle concentration (cmc). Only marginal enhancement of phthalate solubility was observed in solutions containing CTAB below its cmc and beta-CD at low concentrations (less than 5 mM). The solubility enhancements of the plithalates are proportional to the added amount of CTAB and beta-CD. Partition coefficients of the plithalates between monomeric CTAB surfactant and water (K-MN) and between CTAB micelle and water K-MC) were estimated from the experimental data. The mechanisms of solubility enhancements by CTAB and beta-CD were discussed. A log-linear equation was proposed and evaluated for the solubilization by CTAB below cmc, while the previously proposed linear partitioning model was questioned. The structures of the complexes formed between plithalates and beta-CD were proposed, and the formation constants were estimated. The values of log K-MC, log K-MN, and log Kbeta-CD of the plithalates were found to correlate linearly with the log K-OW of plithalates, with the exception of the solid phenyl phthalate.

Investigation of heptakis(2,6-di-O-methyl)-beta-cyclodextrin inclusion complexes with flavonoid glycosides by electrospray ionization mass spectrometry

The non-covalent complexes between three flavonoid glycosides (quercitrin, hyperoside and rutin) and heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD) were investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). The 1:1 complexation of each flavonoid glycoside (guest) to the DM-beta-CD (host) was monitored in the negative ion mode by mixing each guest with an up to 30-fold molar excess of the host. The binding constants for all complexes were calculated by a linear equation in the order: DM-beta-CD:quercitrin > DM-beta-CD:rutin > DM-beta-CD:hyperoside. A binding model for the complexes has also been proposed based on the binding constants and tandem mass spectrometric data of these complexes.

Interfacial supramolecular self-assembled monolayers of C-60 by thiolated beta-cyclodextrin on gold surfaces via monoanionic C-60

The supramolecular self-assembled monolayers (SAMs) of C-60 by thiolated beta-cyclodextrin (CD) on gold surfaces were constructed for the first time using C-60 monoanion. The results indicate that monoanionic C-60 plays a crucial role in the formation of the C-60-containing self-assembled monolayers. The generation of C-60 monoanion and the formation process of C-60 SAMs were monitored in-situ by UV-visible and near-IR spectroscopy. The resulting C-60 SAMs were fully characterized by spectroscopic ellipsometry (SE), cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and water contact angle measurements. After the immobilization of C-60 by the SAMs of thiolated beta-CD, the film thickness increased by approximately 1 nm from 0.8 to 1.8 nm as determined by SE, demonstrating the formation of the supramolecular self-assembled monolayers of thiolated beta-CD/C-60. The new C-60 SAMs exhibited one quasi-reversible redox couple at half wave potential of -0.57 V vs SCE in aqueous solution containing 0.1 M KCl. The surface coverage of C-60 on the gold surfaces was estimated to be 1.1 x 10(-10) mol cm(-2). The XPS showed the assembly of C-60 over the thiolated beta-CD SAMs.

beta-cyclodextrin controlled assembling nanostructures from gold nanoparticles to gold nanowires

In this Letter, P-cyclodextrin (P-CD) was employed as stabilizer in the synthesis of gold nanoparticles. Gold nanoparticles were synthesized by the reduction of HAuCl4 by NaBH4 in the presence of P-CD. Varying the ratio of P-Cl) to HAuCl4, isolated gold nanoparticles could be assembled into nanowires. The nanoparticles and nanowires were characterized by transmission electron microscopy, UV/visible spectroscopy, infrared spectroscopy and X-ray photoelectron spectroscopy. The decreased relative intensity of skeletal and ring vibration in FT-IR spectra and the negative shift of the Au4f(7/2) binding energy in XPS spectra confirmed that beta-CD was chemisorped on An nanoparticles via hydroxyl group.

Detection and characterization of non-covalent complex between lappaconitine and beta-cyclodextrin by electrospray ionization tandem mass spectrometry

The non-covalent complexes between lappaconitine (LA) and beta-cyclodextrin (beta-CD) have been detected and characterized by electrospray ionization combined with ion trap tandem mass spectrometry (ESI-MSn). The experimental results showed that only 1:1 non-covalent complex can be formed in different starting molar ratios of LA to beta-CD. Furthermore, the diagnostic fragmentation of the beta-CD-LA complex, with a significant contribution of covalent fragmentation of LA leaving the N-acetyl anthranoyl (AN) moiety inserted to beta-CD, provided the convincing evidence for the formation of non-covalent complex between LA and beta-CD and the cite of LA molecule included to cavity of beta-CD assigned to AN residue.

Preparation and characterization of a novel beta-cyclodextrin modified poly(N-acetylaniline) film

Hydroquinone was chosen as an electroactive probe to study the beta-cyclodextrin (beta-CD) modified poly(N-acetylaniline) (PNAANI) electrode. The beta-CD modified PNAANI electrode was prepared by electrooxidation of the PNAANI electrode in a beta-CD/DMSO solution. The electrochemical properties of the beta-CD inclusion complex of hydroquinone on the PNAANI electrode and hydroquinone on the beta-CD modified PNAANI electrode were studied. In the cyclic voltammogram of hydroquinone at the beta-CD/PNAANI electrode, DeltaE(p) of the peaks is sharpening and the area of the peaks is increasing, which can be due to the inclusion of hydroquinone into the cavity of beta-CD immobilized at the electrode surface. The beta-CD/PNAANI film was characterized by X-ray photoelectron spectroscopy and H-1 NMR. The mechanism for beta-CD incorporation into the polymer film was also proposed.

Studies on beta-cyclodextrin amino acids inclusion complexes by electrospray ionization mass spectrometry

The positive- and negative-ion electrospray ionization mass spectra of beta-cyclodextrin-amino acids complexes in NH4Ac buffer have been reported in this paper. Compared with positive-ion ESI mass spectra of beta-cyclodextrin-amino acids complexes under the same condition, negative-ion mass spectra obtained for inclusion complexes of beta-cyclodextrin (CD) with tyrosine, phenylalanine and tryptophan, respectively, were completely dominated by deprotonated complex ions and [CD-H](-) ion which is the only daughter ion in collision-induced dissociation (CID) experiment of deprotonated complexes, The results indicated that the charged position for protonated and deprotonated complexes is different from each other. In addition, two complex ions for the same complex have similarly relative dissociation energies, which are higher than that of [CD+NH4](+), indicating that complexes observed in gasphase are not electrostatic adducts at all but complexes formed by hydrogen bonds.

The preparation and stability of the inclusion complex of astaxanthin with beta-cyclodextrin

Inclusion complex of astaxanthin with beta-cyclodextrin was prepared. The water solubility of the inclusion complex was < 0.5 mg/ml, which is better than that of astaxanthin. Large aggregates were observed in the aqueous solution of the inclusion complex. Furthermore, the stability of the inclusion complex against temperature and light was greatly enhanced compared to that of astaxanthin. (c) 2006 Elsevier Ltd. All rights reserved.

Polymethine cyanine dyes in beta-cyclodextrin solution: multiple equilibria and chemical oxidation

Absorption and fluorescence spectroscopy, electrochemical techniques, and semiempirical calculations were employed to characterize the multiple complexation equilibria between two polymethine cyanine dyes (IR-786 and Indocyanine green-ICG, 5) and beta-cyclodextrin (beta-CD, L), as well as the chemical reactivity of the complexed and uncomplexed species against the oxidizing agents hypochlorite (HC) and hydrogen peroxide (HP). IR-786 dimerization is favored with the increase in beta-CD concentration in the form of (SL)(2) complexes. In the case of ICG, free dimers (D) and SL complexes are favored. Both IR-786 and ICG react and discolor in the presence of HC and HP. For IR-786, the reaction with HP and HC proceeds with observed rate constants of 10(-3) and 0.28 s(-1) and second-order rate constants (k(2)) of similar to 10(-3) and 10(4) M(-1) s(-1), respectively. The intermediate species observed in the bleaching reactions of IR-786 and ICG were shown, by cyclic voltammetry and VIS absorption, to result from one electron oxidation. IR-786 complexed with beta-CD is protected against bleaching in the presence of HP and HC by factors of 20 and 4, respectively. This protection was not observed in ICG complexes. Superdelocalizability profile of both dyes and frontier orbital analysis indicates that beta-CD does not protect ICG from oxidation by HP or HC, whereas the 2:2 IR-786/beta-Cd complex is able to avoid the oxidation of IR-786. We concluded that the decrease in the chemical reactivity of the dyes against oxidant agents in the presence of beta-CD is due to the formation of (SL)(2) complexes. Copyright (C) 2010 John Wiley & Sons, Ltd.

Host-guest system of 4-nerolidylcatechol in 2-hydroxypropyl-beta-cyclodextrin: preparation, characterization and molecular modeling

The interaction of 4-nerolidylcatechol (4-NRC), a potent antioxidant agent, and 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was investigated by the solubility method using Fourier transform infrared (FTIR) methods in addition to UV-Vis, (1)H-nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. The inclusion complexes were prepared using grinding, kneading and freeze-drying methods. According to phase solubility studies in water a B(S)-type diagram was found, displaying a stoichiometry complexation of 2:1 (drug:host) and stability constant of 6494 +/- A 837 M(-1). Stoichiometry was established by the UV spectrophotometer using Job`s plot method and, also confirmed by molecular modeling. Data from (1)H-NMR, and FTIR, experiments also provided formation evidence of an inclusion complex between 4-NRC and HP-beta-CD. 4-NRC complexation indeed led to higher drug solubility and stability which could probably be useful to improve its biological properties and make it available to oral administration and topical formulations.

Triangular ruthenium acetate clusters containing the bis(pyridyl)propane ligand and their inclusion chemistry with beta-cyclodextrin

The triruthenium carboxylate cluster [Ru(3)O(OAc)(6)(py)(2)(bpp)](+) (OAc = acetate) containing the bridging 1,3-bis(4-pyridyl)propane (bpp) ligand, and its dimeric species [{Ru(3)O(OAc)(6)(py(2))}(2)(mu-bpp)](2+) were synthesized in order to investigate their inclusion compounds with beta-cyclodextrin (beta-CD). Characterization of the complexes was carried out based on spectroscopic, electrochemical and spectroelectrochemical techniques, while the formation of inclusion complexes was evaluated using (1)H NMR/NOESY spectroscopy. Since bpp is a flexible ligand, a DFT study was carried out in order to characterize its conformational isomers and their possible role in the host-guest chemistry with beta-CD. Instead of observing the formation of inclusion compounds with different stoichiometries, we observed the formation of 1:1 bpp/beta-CD compounds in which the bpp ligand assumes different conformations. The assembly of polymetallic rotaxane species was successfully demonstrated by monitoring the (1)H NMR spectra of the monomeric cluster species in the presence of aquapentacyanoferrate(II) ions and beta-CD.