New ring-opening polymerization via a π-allylpalladium complex

Summary A binary system of a palladium complex as catalyst and zinc alkoxide as initiator conducted a novel ring-opening polymerization of cyclic carbonate, i. e., 5,5-dimethyl-4-ethenyl-1,3-dioxan-2-one. The polymerization proceeded along with releasing carbon dioxide to produce the corresponding polyether. The -allylpalladium complex generated from the monomer with the catalyst is the key intermediate for this new polymerization. The propagating end is zinc alkoxide, which nucleophilically attacks the monomer activated as the -allylpalladium complex in the propagation.     

Synthesis of BCN ceramics from pyrrolidine–Borane complex

BCN ceramics were prepared from pyrrolidine–borane complex. Its complex was a new product and has not appeared on the market. The chemical compositions of the BCN ceramics were BC_1·5N_0·4 obtained at 1000°C in Ar, BC_0·9N_0·4 obtained at 1000°C in NH₃. Boron was a mixture of trigonal and tetragonal BN bonds. Electrical conductivity, of the BCN ceramics showed semiconductive properties. ©     

Di-μ-hydroxy macrocyclic ytterbium(III) complex

The mononuclear [YbracL]Cl₃·2H₂O and dinuclear [Yb₂(OH)₂Cl₂(racL)₂]Cl₂·4CH₃OH·2H₂O complexes of the macrocyclic ligand L derived from trans-1,2-diaminocyclohexane and 2,6-diformylpyridine have been obtained. The formation of the dinuclear species upon addition of hydroxide to the [YbracL]Cl₃·2H₂O or the enantiopure [YbrrrrL(NO₃)₂](NO₃) has been followed using ¹H NMR spectroscopy. The X-ray crystal structure of [Yb₂(OH)₂Cl₂(racL)₂]Cl₂·4CH₃OH·2H₂O complex has been determined. The complex is a dimer consisting of two macrocyclic units. The Yb(III) ion is coordinated by six nitrogen atoms of the macrocyclic ligand, two bridging OH groups and chloride anions. The chiral macrocycle L in this complex exhibits twist-bent conformation of approximate C₂ symmetry.     

Low pressure ethylene oligomerization with a nickel-PÔ complex

Summary The oligomerization of ethylene catalyzed by nickel-PÔ complexes at room temperature and low pressure (5 to 30 bar) yields butenes, hexenes and octenes. The molecular weight distribution can be manipulated by variation of ethylene pressure and by addition of triphenylphosphine. An unexpected linear dependence between the growing factor of the Schulz-Flory type distribution and the pressure has been observed. The equation: =6.2 (PPh₃/Ni)^1.2-[0,17 P(PPh₃/Ni)^1.2] allows to predict the composition of the -olefins formed under different reaction conditions.     

Novel Fe‐based complex oxide catalysts for hydroxylation of phenol

Novel catalysts for the hydroxylation of phenol, Fe–Si–O, Fe–Mg–O and Fe–Mg–Si–O complex oxides, have been synthesized by a coprecipitation method. X‐ray diffraction studies show that MgFe₂O₄ crystallites with spinel structure are formed in Fe–Mg–Si–O and Fe–Mg–O complex oxides and the crystallite size of the metal oxide or complex oxide is reduced after addition of Si. In the hydroxylation of phenol with hydrogen peroxide, Fe‐based complex oxides exhibit high activities after a short induction period. The phenol conversion is improved when silicon is introduced into the Fe‐based complex oxides, and formation of MgFe₂O₄ crystals with spinel structure in the catalysts increases the diphenol selectivity. The addition of a little acetic acid to the reaction liquid can shorten the induction period effectively. Under the same reaction conditions, phenol conversion and diphenol selectivity over the Fe–Mg–Si–O catalyst are close to those over TS‐1, and furthermore, the reaction time is more than ten times shorter as compared to TS‐1. The reaction mechanism of the hydroxylation of phenol on the catalysts has been studied, and a free‐radical mechanism initiated by the formation of phenoxy free radicals is suggested. This revised version was published online in August 2006 with corrections to the Cover Date.     

The asymmetric hydration of 1-octene to (S)-(+)-2-octanol with a biopolymer–metal complex,silica-supported chitosan–cobalt complex

A new biopolymer-non-noble metal catalyst, silica-supported chitosan–cobalt complex (SiO₂–CS–Co), has been prepared by a simple method and found to be a high stereoselective catalyst for asymmetric hydration of 1-octene to (S)-(+)-2-octanol amounted to 97.8%ee when fitting conditions were selected. This catalyst was very stable and could be reused several times without any remarkable change in catalytic activity and optical selectivity. Obviously, the present work has provided a more economical alternative way for the preparation of a chiral 2-octanol.     

Preparation, characterization, and antibacterial activity evaluation of collagen–Zn complex

The different kinds of collagen–Zn complexes were prepared by zinc acetate, zinc chloride, zinc nitrate, and zinc sulfate reacted with collagen protein. Their antibacterial activities have been investigated by MIC method. It was found that the antibacterial activity of collagen–ZnSO₄ complex is better than that of others. To obtain a better antibacterial activity, collagen–ZnSO₄ complexes with different zinc amount were prepared using zinc sulfate as starting material. These complexes were characterized by FT-IR, XRD, and atomic absorption spectrometry. The results showed that zinc ion could chelate with N–H, C–O, and C=O group in collagen to form the stable complex. Antibacterial activities of collagen–ZnSO₄ complexes containing different Zn amount were evaluated against Escherichia coli and Staphylococcus aureus. The results suggested that antibacterial activity increases with the increase of zinc amount.     

Characterization,stability, and pharmacokinetics of sibutramine/β-cyclodextrin inclusion complex

β-Cyclodextrin (β-CD) is widely used to increase the stability, solubility, and bioavailability of poorly soluble drugs because of the appropriate size of its cavity. Sibutramine is a neurotransmitter reuptake inhibitor that has been investigated as an oral anorexiant. Here we report the complexation of sibutramine base with β-CD and the stability, dissolution, and pharmacokinetic properties of the sibutramine/CD complex. The formation of sibutramine/β-CD inclusion complexes is confirmed using differential scanning calorimetry, X-ray diffractometry, and ¹H nuclear magnetic resonance. The thermal and photochemical stability of sibutramine is significantly improved by the complexation with β-CD, and the pharmacokinetic parameters (e.g., the plasma concentration, area under the curve, and maximum concentration of two active metabolites) for humans are comparable with those of the commercialized standard product (Reductil^®). Our study suggests that sibutramine/β-CD complexation can be of great use to increase the stability and biological efficacy of sibutramine base.     

Structure–rheology relationship in complex quaternized polysulfones/solvent/nonsolvent systems

Polymer chains consisting of water-soluble polysulfones with various amounts of ionic chlorine have been prepared via the quaternization reaction of chloromethylated polysulfones with N,N-dimethylethanolamine. Rheological investigations have reflected the importance of electrostatic interactions, hydrogen bonding, and association phenomena from the ternary systems consisting of a proton-acceptor polymer (polysulfones with different ionic chlorine content), a proton-donor solvent (N,N-dimethylformamide), and a proton-donor solvent (methanol). The specific interactions, the polyelectrolyte effect induced by enhanced dissociation of the ionizable groups and mixed solvents’ quality modify the rheological functions, i.e., dynamic viscosity, elastic shear modulus and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent energy of activation and flow activation entropy. These results were correlated with the surface properties of the polysulfonic films formed from solutions in solvent/nonsolvent mixtures.     

Online process monitoring for complex systems with dynamic weighted principal component analysis☆

Conventional multivariate statistical methods for process monitoring may not be suitable for dynamic processes since they usually rely on assumptions such as time invariance or uncorrelation. We are therefore motivated to propose a new monitoring method by compensating the principal component analysis with a weight approach. The proposed monitor consists of two tiers. The first tier uses the principal component analysis method to extract cross-correlation structure among process data, expressed by independent components. The second tier estimates auto-correlation structure among the extracted components as auto-regressive models. It is therefore named a dynamic weighted principal component analysis with hybrid correlation structure. The essential of the proposed method is to incorporate a weight approach into principal component analysis to construct two new subspaces, namely the important component subspace and the residual subspace, and two new statistics are de-fined to monitor them respectively. Through computing the weight values upon a new observation, the proposed method increases the weights along directions of components that have large estimation errors while reduces the influences of other directions. The rationale behind comes from the observations that the fault information is associated with online estimation errors of auto-regressive models. The proposed monitoring method is exem-plified by the Tennessee Eastman process. The monitoring results show that the proposed method outperforms conventional principal component analysis, dynamic principal component analysis and dynamic latent variable. ? 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.     

Electronic structure and bonding in the platinum–silylene complex [PtSiH2]

Relativistic ab initio molecular orbital calculations have been performed on the monoligated neutral complex [PtSiH₂] in order to investigate the nature and energetics of the interaction between the metal and SiH₂ ligand. The results suggest that the silylene ligand acts as both a σ-donor and π-acceptor but is a relatively better π-acceptor. The electronic structure of [PtSiH₂] is analyzed in detail as measured by Wiberg’s bond indices, charge distributions and orbital populations.     

Preparation and electrochemical behavior of water-soluble inclusion complex of ferrocene with β-cyclodextrin polymer

A new water-soluble inclusion complex of ferrocene (Fc) with β-cyclodextrin polymer (β-CDP) was prepared by a facile strategy and characterized by ¹H NMR spectroscopy, elemental analysis, powder X-ray diffractometry, thermogravimetry, UV–vis spectroscopy and cyclic voltammetry. Compared with Fc and the inclusion complex of Fc with β-cyclodextrin (Fc-β-CD), the solubility of ferrocene-β-cyclodextrin polymer (Fc-β-CDP) was greatly enhanced due to the water-soluble β-CDP host. The ratio of β-cyclodextrin (β-CD) unit in β-CDP to Fc was determined as 1:1. At 25 °C, the dissociated constant of Fc-β-CDP was measured as 3.65 mM by UV–vis spectroscopy and cyclic voltammetry. The electrochemical properties of Fc-β-CDP in water were studied. The diffusion coefficients of oxidation state and reduction state were calculated as 3.52 × 10⁻⁷ cm² s⁻¹ and 3.93 × 10⁻⁷ cm² s⁻¹. The resulting value of standard rate constant was measured as 1.95 × 10⁻³ cm s⁻¹. The diffusion activation energy was calculated as 21.8 kJ mol⁻¹.     

Flame-retardant epoxy resin with good smoke-suppression endowed by chitosan–cobalt/phosphorus complex

Chitosan-based flame-retardant CS–Co–DOPA (CCD) was synthesized by the neutralization reaction of 10-hydroxy-9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide (DOPA) with chitosan-cobalt complex and fully characterized by scanning electron microscopy (SEM), energy-dispersive spectrometer, x-ray diffraction, X-ray photoelectron spectroscopy (XPS), optical emission spectrometer, and Fourier transform infrared (FTIR) characterizations. The epoxy resin (EP) modified with CCD exhibited good flame retardancy. With the addition of 5 wt% CCD, the EP/CCD achieved UL-94 V-1 rating and possessed limiting oxygen index (LOI) value of 30%. Cone calorimetry (CC) test demonstrated that EP/CCD resulted in a remarkable reduction of peak smoke production rate (pSPR) and total smoke production (TSP) by 63% and 40%, respectively, showing an outstanding smoke suppression. The char residue obtained from the CC test was further characterized using SEM, FTIR, Raman, and XPS techniques. The results revealed that CCD facilitated the formation of a dense and compact char layer on EP during combustion, thereby impeding gas and heat transfer. In addition, TG-IR was employed to investigate the gas-phase flame-retardant effect of EP/CCD composites, which revealed that CCD promotes the release of water, CO_2, and other incombustible gases, altering the decomposition path of EP.     

Fluoroalcohol-mediated reductive iodonio-Claisen rearrangement: Synthesis of complex ortho-substituted-allyl iodoarenes? ?

Reductive iodonio-Claisen rearrangement (RICR) involving λ³-iodanes and allyl or substituted-allyl silanes in fluoroalcohols, such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE), was studied for the synthesis of complex ortho-allyl or substituted-allyl iodoarenes. In comparison to the previously reported condition involving boron trifluoride diethyl etherate, the RICR mediated by fluoroalcohols was found to proceed more effectively. The resulting complex ortho-allyl iodoarenes are useful synthetic intermediates and can be readily converted to various heterocyclic compounds.     

Gelatin–κ-carrageenan polyelectrolyte complex hydrogel compositions for the design and development of extended-release pellets

Present investigation was aimed to develop Zaltoprofen-loaded extended-release (ER) pellets formulation for prolonged release. The matrix type of pellets was prepared by extrusion-spheronization technique using calcium chloride-mediated gelatin–κ-carrageenan (G–κ-Carr) polyelectrolyte complex (PEC) hydrogel using rotatable central composite design. The pellets were characterized for physicochemical, morphological, solid-state characterization and flow properties. The formulations were also estimated for drug release and mucoadhesion potential. The optimized formulation (F1) containing 5:5 ratio of G–κ-Carr showed a drug release up to 98.2% and mucoadhesion of 95%. Optimized formulation showed acceptable release pattern, and hence would be viable alternative to ER type of formulations.