以对-(4-烯丙氧基苯甲酰氧基)苯甲酸对-甲氧基苯酚酯为单体的液晶聚硅氧烷的合成与表征

侧链型液晶聚合物是目前很有兴趣的研究课题之一。在国内,有关的研究报道也逐渐增多,本工作设计并合成了对-(4-烯丙氧基苯甲酰氧基)苯甲酸对-甲氧基苯酚酯单体,其结构式为:     

The catalyzed hydrosilation reaction: substituent effects

Ab initio electronic structure calculations using MP2 wavefunctions have been used to investigate a reaction path for the hydrosilation reaction catalyzed by divalent titanium [modeled by TiH₂, TiCl₂, and Ti(C₅H₅)₂]. Optimized structures and energies are presented. All model reactions predict a barrierless reaction path compared to a barrier of 78 kcal/mol for the uncatalyzed reaction. Received: 11 August 1998 / Accepted: 3 September 1998 / Published online: 23 February 1999     

The uncatalyzed hydrosilation reaction

Summary The reactions of ethylene with silane, chlorosilane, fluorosilane, and dichlorosilane, and of propylene with silane are considered usingab initio electronic structure calculations. At both the MP2 and MP4 levels of theory with both DZP and TZP quality basis sets, the energy barriers for all reactions are found to be in excess of 50 kcal/mol.     

Platinum(II)-bis-(N-heterocyclic carbene) complexes: synthesis, structure and catalytic activity in the hydrosilylation of alkenes

Chelating biscarbene ligands increase the stability of metal-organic catalyst systems. The catalytic activities of seven structurally different platinum(II)-bis-NHC-complexes in the hydrosilylation of alkenes have been investigated and compared with the catalytic activity of the Karstedt catalyst and of a highly active platinum(0)-NHC-complex. It is shown that a fine-tuning of the catalytic activity of the platinum(II)-bis-NHC-complexes is possible. The synthesis of a platinum(II)-bis-NHC-complex with similar activity, but additional advantages compared to the Karstedt catalyst, is reported. The solid state structure of 1,1-[Bis(3,3′-(4-methoxyphenyl)-1,1′-1H-imidazolium-2,2′-ylidene)methanediyl]platinum(II)-dichloride is presented.     

Substrate binding and activation via pendant hydrogen-bonding groups as an approach to biomimetic homogeneous catalysis

In a biomimetic approach to organometallic catalysis, pendant hydrogen-bonding groups are shown to influence the chemistry of ligand binding and activation in an iridium complex. Such groups can bind a substrate by hydrogen bonding and so offer the possibility of a biomimetic approach to catalysis where binding is controlled via molecular recognition. Because catalyst design in this area may be challenging, combinatorial and rapid screening methods may be needed to assay potential catalysts and initial progress on developing these methods for hydrosilation of alkenes and imines is described. Catalysis of aldehyde imination and the origin of pK_a changes of bound H₂ are discussed.     

Synthesis and reactions of poly[(ethoxysilylene)phenylenevinylene]s and chain-to-pendant energy transfer in the resulting polymer

Reactions of (bromophenylethenyl)diethoxysilanes with magnesium in THF gave poly[(ethoxysilylene)phenylenevinylene]s. The ethoxy group of the polymers could be readily replaced with other substituents by treating them with nucleophiles. Optical properties of the resulting poly(silylenephenylenevinylene)s were examined with respect to their UV absorption and emission spectra. Of those, pyrenylethynyl-substituted one exhibited energy transfer from the backbone to the substituent in the photo-excited state.     

Studies on the Hydrosilation of Aromatic Aldehydes

The dependence of reactivity on molecular structure in hydro-silation of aromatic aldehydes catalyzed by (PPh3)3 RhCl was studied by “IN SITU” FT-IR technique and a plausible mechanism was proposed.The results show that: (1) Model reaction Ⅰ, Ⅱ and Ⅲ are all characterized by an induction period; (2) The reaction constant of model reaction Ⅰ is +1.57, so the rare of reaction Ⅰ is increased by the electron-withdrawing groups; (3) The rate of model reaction Ⅲ decreases when the size of R1 becomes larger; (4) The reaction constant of model reaction Ⅲ is -0. 50, so the rate of it is increased by electron-donating groups.     

Synthesis and characterization of chemically bonded stationary phases on hydride surfaces by hydrosilation of alkynes and dienes

A hydrosilation reaction was used to bind four compounds with one or more alkyne groups or two alkene functionalities. The diffuse reflectance infrared Fourier transform, the 29Si cross-polarization magic-angle spinning (CP-MAS) NMR, and the 13C CP-MAS NMR spectra were used to characterize the various bonded materials. The bonded phase density was determined from carbon elemental analysis. The two ten-carbon hydrophobic stationary phases were characterized chromatographically and static stability tests were run in acidic and basic solutions.     

A NOVEL SUPRAMOLECULAR CLATHRATE OF RODLIKE p-BUTOXYBENZYLIDENE-p′-DODECOXYANILINE TRAPPED WITHIN POLYORGANOSILOXANE PORE*

A novel supramolecular polysiloxane clathrate, POS/C, has been preparedby in-situ encapsulating rodlike p-butoxybenzylidene-p ' - dodecoxyaniline (BBDA ) , one kindof Schiff base liquid crystal molecule, within the pore of polyorganosiloxane (POS) whichis prepared by hydrosilylation coupling reaction of polyvinylsilsesquioxane (Vi- T ) withtetramethyldisiloxane (H-MM). Investigation by polarized light microscopy (PLM), differ-ential scanning calorimetry (DSC), infrared spectroscopy (IR), atomic force microscopy(AFM) and molecular simulation gives a preliminary support to the existence of the titlesupramolecular clathrate.