Phenylsilane Research Articles

Synthesis and properties of polysilanes with tetrathiafulvalene as pendant group

Two polysilanes with tetrathiafulvalene (TTF) as pendant groups were synthesized by reaction of 2-cyanoethyl substituted TTF 1 with (chloromethylphenyl)dimethyl(phenyl)polysilane, or reaction of 4-vinylphenyl-TTF 2 with poly[methylsilane-co-methyl(phenyl)silane]. The structures and properties of TTF-polysilanes and their intermediates were characterized by 1H NMR, mass, GPC, UV/Vis, IR and cyclic voltammetry (CV). The results of UV/Vis and CV of these polysilanes indicated interaction between the TTF moieties and σ-electron delocalized Si–Si chain in the ground states. These polysilanes doped by I2 exhibited high conductivities (10−2 S cm−1).

On the Similarity and Difference of Molecular Structure and Packing Between Organopolysilanes with Symmetric and Asymmetric Side-Chains

Molecular structure and packing of various organopolysilanes with symmetric and asymmetric side-chains have been obtained by comparing the theoretical X-ray diffraction pattern with the experimental pattern. Molecular structure of the organopolysilanes with asymmetric side-chains, such as, poly(methyl propyl silane) and poly(methyl phenyl silane), is mainly determined by the intra-molecular van der Waals interaction between the adjacent side-chains, which is similar to that of the organopolysilanes with symmetric side-chains, such as, poly(di-methyl silane) and poly(di-propyl silane). Packing of the organopolysilanes is determined to occupy closely in space in both cases. However, density of the organopolysilanes with asymmetric side-chains is smaller than that of the organopolysilanes with symmetric side-chains because of the large space between the adjacent side-chains.

Photoreactions of 4,4'-Bis(pentamethyldisilanyl)biphenyl

report-ed that the photolysis of 4-(trifluoromethyl)phenylpenta-methyldisilane in ethanol-hexane mixture affords 4-(tri-fluoromethyl)phenyldimethylsilane, (trimethylsilyl)[(eth-oxydimethyl)silyl](trifluoromethyl)cyclohexadienes, and 4-(trifluoromethyl)phenyl(ethoxydimethyl)silane in 24, 41,and 15% yields, respectively. In this reaction, it wasconcluded that 4-(trifluoromethyl)phenyldimethylsilane wasformed through the nucleophilic attack of ethanol at the β-silicon atom of the disilane moiety. In the photolysis of

Efficient Enantioselective Hydrosilylation of Aryl Ketones Catalyzed by a Chiral BINAP‐Copper(I) Catalyst‐Phenyl(methyl)silane System.

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Efficient Enantioselective Hydrosilylation of Aryl Ketones Catalyzed by a Chiral BINAP‐Copper(I) Catalyst‐Phenyl(methyl)silane System

AbstractThe Cu(I)‐chiral diphosphine (BINAP) system was found to efficiently catalyze the hydrosilylation of aryl alkyl ketones with excellent enantioselectivities by using phenyl(methyl)silane as stoichiometric hydride source.

Phosphorus–phosphorus coupling in a diphosphine with a ten bond P⋯P separation

The large, unsymmetrical diphosphine 5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinomethoxy)-27(or 28)-benzoyloxy-28(or 27)-hydroxycalix[4]arene, in which the phosphorus atoms are separated by ten bonds, was prepared by monobenzoylation of 5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinoylmethoxy)-27,28-bis(hydroxy)calix[4]arene, followed by reduction with phenyl silane. Its molecular structure has been determined by X-ray crystallography. In the solid state, the phosphorus atoms are separated by 5.333(1) A. NMR investigations reveal an unexpected "through-space"J(PP') coupling constant of 8.0 Hz and also show that, in solution, the calixarene is conformationally mobile, the phenoxy ring flipping rapidly through the calixarene annulus. The spatial proximity of the two phosphorus atoms was further demonstrated by the ease of obtaining the cis-chelate complex [Pd(eta3-C3H4Me)(THF)2]BF4 (THF = tetrahydrofuran).

Reaction of Germanium Tetrachloride with Chloro(phenyl)silanes in the Presence of Aluminum Chloride

The effect of the quantity of aluminum chloride on the direction and depth of reaction of germanium tetrachloride with chloro(phenyl)silanes of the general formula PhnSiCl4−n (n = 1 – 3) was studied to show that radical exchange between germanium and silicon is initiated only if the mixture contains no less than 2.5–5 wt % of aluminum chloride. With trichloro(phenyl)silane, the radical exchange is initiated at 5 wt % of aluminum chloride and results in exclusive formation of trichloro(phenyl)germane. The reactions of GeCl4 with dichlorodiphenylsilane and chlorotriphenylsilane in the presence of 2.5–7.5 wt % of aluminum chloride give dichlorodiphenylgermane as the major product, and at AlCl3 concentrations of above 10 wt % the major product becomes to be trichloro(phenyl)germane.

Excitations in oligosilanes with photochromic side groups

A quantum mechanical study of conformations, electronic densities, and absorption spectra of neutral and cation-radical hepta[methyl(phenyl)silanes] (7MPSi) substituted with a photochromic spiropyran derivative (SP/MR) was performed. 7MPSi-SP exhibit similar differences between the neutral and cation-radical conformation as unsubstituted 7MPSi, while 7MPSi-MR do not show any significant main chain conformation differences between the neutral and positively charged macromolecule. Population analysis shows that the positive charge in the cation-radical of 7MPSi-SP is located on the main chain, while in the cation-radical of 7MPSi-MR it is located on the photochromic unit.

Incidence of microflora and of ochratoxin A in green coffee beans (Coffea arabica)

Coffee is produced in tropical countries around the Equator where climatic conditions are favourable for fungal development and mycotoxin production; however, mycotoxins do not only occur in the tropical countries. The aim was to evaluate the mycoflora and possible incidence of ochratoxin A (OTA) in 60 samples of green coffee beans from Brazil. The mycological evaluation was carried out using a conventional method and the OTA was determined using sequential phenyl silane and immunoaffinity column cleanup followed by HPLC. The detection limit was 0.2 μg kg−1. Practically all samples (91.7%) were contaminated with moulds. The dominant fungal genus was Aspergillus, including A. niger (83.3%), A. ochraceus (53.3%) and A. flavus (25.0%). The occurrence and the levels of the genus Cladosporium (16.6%) and Penicillium (10.0%) were substantially lower than Aspergilli. Twenty samples (33.3%) of 60 were contaminated with the toxin at levels ranging from 0.2 to 7.3μg kg−1. The average concentration was 2.38 μg kg−1. All positive samples showed OTA levels below the limit suggested by the European Union (8 μg kg−1).

Mutagenic activity of structurally related oxiranes and siloranes in Salmonella typhimurium

Ring-opening molecules like oxiranes (epoxides) maybe suitable for the development of non-shrinking dental composite materials. Since oxiranes are reactive molecules, they can cause adverse biological effects in living organisms. The introduction of siloranes, a merger of silane and oxirane, may solve this problem. Here, new oxiranes and siloranes were analyzed for the induction of mutations in Salmonella typhimurium (TA97a, TA98, TA100, and TA102), and a reactive oxirane molecule served as a reference. This chemical, epoxy cyclohexyl methyl-epoxy cyclohexane carboxylate (Est-Ep) tested positive in S. typhimurium TA100. The numbers of mutants were about 3–10-fold higher than controls in the presence of a metabolically active S9 fraction isolated from rat liver. Only a weak mutagenic effect was observed after direct testing (without S9). Di(cyclohexene-epoxidemethyl)ether (Eth-Ep) also caused a slight increase of mutant numbers in TA100 both in the presence and absence of S9. In contrast, no effects were detected with the large oxirane molecules, 2,2-bis(4,1-phenylenoxy-3,1-propanediyl-3-oxatricyclo [3.2.1.0 2,4]octylcarboxy) propylidene (Nor-BP-Ep) and 2,2-bis(4,1-phenylenoxy-3,1-propanediyl-3,4-epoxycyclo-hexylcarboxylic-acid) propylidene (Est-BP-Ep). As to the siloranes, 1,4-bis(2,3-epoxypropyloxypropyl-dimethylsilyl)-benzene (Phen-Glyc) was a direct mutagen in S. typhimurium TA100 and TA102. This weak but dose-related increase of revertants was even enhanced by S9. Other siloranes, like di-3,4-epoxy cyclohexylmethyl-dimethyl-silane (DiMe-Sil), methyl-bis[2-(7-oxabicyclo[4.1.0]hept-3-yl)phenyl silane (Ph-Sil), and 1,3,5,7-tetrakis(ethyl cyclohexane epoxy)-1,3,5,7-tetramethyl-cyclotetrasiloxane (TET-Sil) tested negative in all S. typhimurium strains. All compounds will be further analyzed for the formation of chromosomal aberrations in mammalian cell cultures.

Conformation changes of polysilanes during the polaron formation

Abstract Quantum mechanical studies of polaron formation in oligo[methyl(phenyl)silane] (OMPSi) was performed. The conformations of the neutral, positively and negatively charged OMPSi were optimized by means of B3LYP method. For the evaluation of the substituent effects, the conformation of the unsubstituted oligosilane chain was also calculated. The negative polaron conformation shows a significant stretching of the chain, whereas the positive polaron conformation is shrunk. This fact is associated with changes of electron density distribution. There is also a strong influence of the π-conjugated substituent on the conformation of the negative polaron. On the other hand, the influence of the substituents on the conformation of the positive polaron is small. The absorption spectra of the defect-free and polaron oligomers are discussed.

Syntheses of enantiopure Si-centrochiral silicon-based muscarinic antagonists using an enantioselective enzymatic esterification as the key step

The muscarinic antagonists (R)-cyclopentyl(hydroxymethyl)phenyl[2-(piperidin-1-yl)ethyl]silane[(R)-1] and(R)-1-{2-[cyclopentyl(hydroxymethyl)phenylsilyl]ethyl}-1-methylpiperidinium iodide [(R)-2] were synthesized using anenantioselective enzymatic transformation as the key step. Apapain-catalyzed (E.C. 3.4.22.2) esterification ofrac-cyclopentyl(hydroxymethyl)phenyl(vinyl)silane(rac-3) with 5-phenylpentanoic acid afforded(R)-cyclopentyl(phenyl)[(5-phenylpentanoyloxy)methyl]vinylsilane[(R)-4] which upon chemical hydrolysis gave enantiomericallyenriched (R)-3 (68% ee). Repetition of thisesterification/hydrolysis sequence, starting from enantiomericallyenriched (R)-3, finally gave the enantiopure silane (R)-3(≥98% ee) which served as the starting material for thesubsequent chemical synthesis of (R)-1 and (R)-2{(R)-3 →(R)-cyclopentyl(phenyl)[(trimethylsilyloxy)methyl]vinylsilane[(R)-5] → (R)-1 → (R)-2}.

Optical Correlation System Based on Photorefractive Polymer and Polysilane Phase Mask

Modification of the refractive index of polysilanes due to the UV-photodecomposition and its application to phase mask were investigated. From the wavelength dependence of UV-photodecomposition in the poly[methyl(phenyl) silane] (PMPS) film, the refractive index was found to be effectively lowered by eliminating phenyl side-group with shorter wavelength UV light. It was also confirmed that the phase difference information could be recordable by utilizing such refractive index changes in PMPS films. Utilizing the 4-f matched-filter architecture based on the four-wave mixing with photorefractive polymers as the optical correlator, the occurrence of large correlation signal was successfully observed only when the image written in the PMPS phase mask was coincident with the phase difference pattern on the PMPS film as a reference. This result indicates that the polysilane films with UV-photodecomposition pattern can be useful for the phase difference mask in the optical correlation system.

Increase of photoluminescence from fullerene‐doped polymers under laser irradiation

AbstractPhotoluminescence (PL) from fullerene (C60 and C70)‐doped polymers such as poly(methyl methacrylate) (PMMA), polystyrene (PS), poly(methyl phenyl silane) (PMPS) and poly(phenyl silsesquioxane) (PPSQ) increases gradually under laser irradiation in air (but not in vacuum and in nitrogen) and eventually becomes visible to the naked eye. Concomitantly, the PL peak is broadened and, in most cases, blue‐shifted. No such PL increases are observed for pure C60 films made by vacuum vapor deposition and pure polymer films. Among the polymers used, fullerene‐doped PMMA has the greatest PL increase after several hours of laser irradiation and fullerene‐doped PMPS has the highest rate of PL increase at the initial stage of the laser irradiation. To gain an insight into the mechanism of the PL increase, laser‐irradiated fullerene‐doped PMMA samples were analyzed by UV‐Vis spectrophotometer, FT‐IR, mass spectrometry, GPC and NMR. The results show that the PL increase can be attributed to CH60On‐polymer (or C70On‐polymer) and oxidized fullerene‐polymer adducts formed by some laser‐induced photochemical reactions among fullerenes, oxygen and polymers.

Using linear and branched polysilanes for the photoinitiated polymerization of a commercial silicone-acrylate resin.: A real time FTIR study

The photo-crosslinking of a silicone-based oligomer, bearing pendant acrylate groups, has been carried out using linear polysilanes (poly(methyl phenyl silane), poly(methyl- n-propyl silane), poly(di- n-hexyl silane)) and a branched one, poly( p-butylphenyl phenyl silane-co-phenyl silyne), as initiators. The curing rate was measured with the aid of the real time Fourier transformed infrared spectroscopy. Apart from the neat oligomer also formulations containing reactive diluents, i.e. acrylic and vinyl ether monomers were photo-cured. An excellent curing performance (final conversion of about 95%) was achieved with a 1:1 (w:w) blend of the oligomer with 2-ethyl hexyl methacrylate (EHMA). n-Butyl vinyl ether (BVE) was found to copolymerize with the pendant acrylate groups. Moreover, in the presence of diphenyl iodonium chloride it homopolymerized simultaneously by a cationic mechanism. In this way interpenetrating structures were formed. The iodonium ions oxidize some of the photo-generated silyl radicals thus producing initiating cations.

Combined Phenyl Silane and Immunoaffinity Column Cleanup with Liquid Chromatography for Determination of Ochratoxin A in Roasted Coffee: Collaborative Study

A collaborative study was conducted to evaluate a liquid chromatography (LC) method for ochratoxin A using sequential phenyl silane and immunoaffinity column cleanup. The method was tested at 3 different levels of ochratoxin A in roasted coffee, which spanned the range of possible future European regulatory limits. The test portion was extracted with methanol and sodium bicarbonate by shaking for 30 min. The extract was filtered, centrifuged, and then cleaned up on a phenyl silane column before being eluted from the washed column with methanol-water. The eluate was diluted with phosphate-buffered saline (PBS) and applied to an ochratoxin A immunoaffinity column, which was washed with water. The ochratoxin A was eluted with methanol, the solvent was evaporated, and the residue was redissolved in injection solvent. After injection of this solution onto a reversed-phase LC apparatus, ochratoxin A was measured by fluorescence detection. Eight laboratory samples of low-level naturally contaminated roasted coffee and 2 laboratory samples of blank coffee (< 0.2 ng/g ochratoxin A at the signal-to-noise ratio of 3:1), along with ampules of ochratoxin A calibrant and spiking solutions, were sent to 15 laboratories in 13 different European countries. Test portions of the laboratory samples were spiked at levels of 4 ng/g ochratoxin A, and recoveries ranged from 65 to 97%. Based on results for spiked blank material (blind duplicates) and naturally contaminated material (blind duplicates at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 2 to 22% and the relative standard deviation for reproducibility (RSDR) ranged from 14 to 26%. The method showed acceptable within- and between-laboratory precision, as evidenced by HORRAT values, at the low level of determination for ochratoxin A in roasted coffee.

Refractive Index Modification Due to the Uv-Photodecomposition of Polysilane and Its Application as Phase Mask

The development of phase mask using the refractive index variation due to the UV-photodecomposition of the polysilane was examined. It was proven that the refractive index due to the UV-photodecomposition of the poly[methyl(phenyl)silane] changed from 1.70 to 1.56 by means of the ellipsometry measurements. Furthermore, it was confirmed that information of the phase difference could be recorded by providing the pattern of the UV photodecomposition of the polysilane.

Characterization and properties of new silicone-containing epoxy resin

A new epoxy monomer, triglycidyloxy phenyl silane (TGPS) has been synthesized. By curing of TGPS, Epon 828 and DER 732, with 4,4-diaminodiphenyl methane (DDM), the curing rate and conversion efficiency of these epoxy resins are in the order of TGPS>Epon828>DER732. In the mixed epoxy system of TGPS/Epon 828/DDM, homogenous products are obtained from all proportions. In addition, the glass transition temperature of the blend decreases with increasing amount of TGPS from 140 to 100°C. By using TGA in a N2 environment, the onset decomposition temperature of silicone-containing epoxy resin system of TGPS is 80°C lower than that of Epon 828, and the decomposition of TGPS is a two-stage process with maxima weight loss rates at 330 and 430°C, respectively. The first stage involves the breaking of the silicone-containing group in TGPS and the second-stage is carbonization. In the second stage of carbonization, the temperature for maximum weight loss rate is 15°C higher than that of the Epon 828 in the first stage. This result indicates that the silicone-containing group is in favor of the carbonization mechanism and the solid char yield at 800°C for TGPS is 40wt%. Based on EDX analysis on the surface elements, the presence of Si and C is indicative of the above observation. In addition, the result by using TGA in an air environment shows that the silicon-containing carbon residue is superior in preventing oxidative burning. The high limiting oxygen index (LOI) of TGPS at 35 is considered as an excellent flame retardant in the epoxy system.

Quasiparticles in σ-conjugated polymers

Conformations of quasiparticle defects (positive and negative polaron and exciton) of oligosilanes consisting of up to 10 repeating units are determined. The polaron conformations computed by the ROHF, UHF and B3LYP methods are compared. Conformations of the positive and negative polarons of oligo[methyl(phenyl)silane] (six repeating units) are determined by means of the ROHF and B3LYP methods. Conformation of the exciton is determined by means of the ab initio configuration interaction (CIS) method. The results are compared with those for the unsubstituted oligosilane.

Rapid production of silicon-containing vapor grown carbon fibers using the liquid pulse injection technique

Silicon containing vapor grown carbon fibers have been rapidly produced from a mixture of benzene and phenyl silane, using the liquid pulse injection technique. Fibers with lengths up to 20 mm were obtained within 1 min at a carbon yield of 0.23. The inclusion of silicon led to the improvement in the oxidation resistivity of the fibers. Moreover, the obtained fibers possessed tensile strengths and electrical resistivities comparable to those of fibers without silicon inclusion. Electrochemical analysis suggests that the included silicon is highly dispersed within the structure of the fibers.