Synthesis of Organic-Inorganic Hybrid Particles by Sol-Gel Chemistry

The synthesis of ORganically MOdified SILica (ORMOSIL) particles has been carried out using both the hydrolytic and non-hydrolytic sol-gel routes. The hybrid (nano)composites are organically modified with an alkyl or aryl group covalently bonded to silicon. Hybrids have been synthesised in an aqueous sol-gel process by a modified Stöber route, producing spherical nanoparticles with diameters in the range 50–300 nm. The size of the particles can be controlled by control of certain reaction parameters. Smaller ormosil nanoparticles can be synthesised by a base-catalysed emulsion polymerisation route, by varying the type and concentration of surfactant and precursor feed rate. In this case, particles in the size range 3.5–10 nm can be obtained. Hybrids have been synthesised from hyperbranched polyesters by encapsulation in a silica matrix using the hydrolytic sol-gel route. Optimisation of the reaction conditions allows the hybrids to be produced as isolated sub-micron spherical particles. Ormosil particles have also been synthesised using the non-hydrolytic sol-gel route, which may lead to products of different morphologies because of the different polarity of the reaction medium. Different reaction conditions were studied in order to optimise the size and shape of the particles, including choice of solvent, use of surfactants and addition of polystyrene. Dimethylsulfoxide acts as a novel oxygen donor for the catalyst-free formation of colourless silsesquioxanes.     

Multicenter ligand transformations of thioureas on ruthenium clusters

The reaction of trirutheniumdodecacarbonyl with various thioureas was found to give, depending upon the substituents and the reaction conditions, a large variety of tri-, tetra-, penta-, and hexanuclear ruthenium clusters. The ligand systems observed in the products are derived from the thioureas employed; the fragmentation of the thiourea molecules involve N-H, C-S, C-H, and C-N activation processes.     

Novel blue‐greenish electroluminescent poly(fluorenevinylene‐alt‐dibenzothiophenevinylene)s and their model compounds

Poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐2,8‐vinylene) (PS) and poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐5,5‐dioxide‐2,8‐ vinylene) (PSO) as well as corresponding model compounds were synthesized by Heck coupling. Both the polymers and model compounds were readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane, chloroform, and toluene. The polymers showed a decomposition temperature at ～430 °C and a char yield of about 65% at 800 °C in N₂. The glass‐transition temperatures of the polymers were almost identical (75–77 °C) and higher than those of the model compounds (26–45 °C). All samples absorbed around 390 nm, and their optical band gaps were 2.69–2.85 eV. They behaved as blue‐greenish light emitting materials in both solutions and thin films, with photoluminescence emission maxima at 450–483 nm and photoluminescence quantum yields of 0.52–0.72 in solution. Organic light‐emitting diodes with an indium tin oxide/poly(ethylene dioxythiophene):poly(styrene sulfonic acid)/polymer/Mg:Ag/Ag configuration with polymers PS and PSO as emitting layers showed green electroluminescence with maxima at 530 and 540 nm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6790–6800, 2006     

Efficient synthesis of an imidazole-substituted delta-amino acid by the integration of chiral technologies

Two methods to produce (2S)-5-amino-2-(1-n-propyl-1H-imidazol-4-ylmethyl)-pentanoic acid were investigated. Diastereoisomeric salt resolution, using the quinidine salt, gave the desired intermediate in 98% ee and 33% yield. Asymmetric hydrogenation of various substrates gave high conversions, with up to 83% ee. Integration of these two approaches via asymmetric hydrogenation of a quinidine salt substrate followed by crystallization provided the desired intermediate in 94% ee and 76% yield.     

Win X-ray: a new Monte Carlo program that computes X-ray spectra obtained with a scanning electron microscope.

A new Monte Carlo program, Win X-ray, is presented that predicts X-ray spectra measured with an energy dispersive spectrometer (EDS) attached to a scanning electron microscope (SEM) operating between 10 and 40 keV. All the underlying equations of the Monte Carlo simulation model are included. By simulating X-ray spectra, it is possible to establish the optimum conditions to perform a specific analysis as well as establish detection limits or explore possible peak overlaps. Examples of simulations are also presented to demonstrate the utility of this new program. Although this article concentrates on the simulation of spectra obtained from what are considered conventional thick samples routinely explored by conventional microanalysis techniques, its real power will be in future refinements to address the analysis of sample classifications that include rough surfaces, fine structures, thin films, and inclined surfaces because many of these can be best characterized by Monte Carlo methods. The first step, however, is to develop, refine, and validate a viable Monte Carlo program for simulating spectra from conventional samples.     

All-trans-1-acyloxy-1,3-pentadiene-5 ols as reactive dienes in new intramolecular diels-alder reactions

The high reactivity of the $\text{all-trans}$-1-acyloxy-1,3-pentadiene-5-ols as dienes in intramolecular Diels-Alder reactions with maleic anhydride and fumaric acid ethylester monochloride is discussed.     

Comment: 2004's fastest organic and biomolecular chemistry!

In January 2003, the Royal Society of Chemistry launched Organic & Biomolecular Chemistry (OBC)--a journal promising to provide high quality research from all aspects of synthetic, physical and biomolecular organic chemistry. The journal was set to build upon the foundations laid down by its predecessor publications (J. Chem. Soc., Perkin Trans. 1 and J. Chem. Soc., Perkin Trans. 2) as well as complement the subject coverage already published in prestigious general chemistry journals such as Chemical Communications and Chemical Society Reviews. Nearly two years on, just how is the programme developing and what can the community expect to see from the Royal Society of Chemistry (RSC)?     

Wittig and horner-wittig coupling reactions of 2-substituted cyclic ethers and their application to spiroketal synthesis

Wittig and Horner-Wittig coupling reactions of tetrahydropyran or tetrahydrofuran 2-triphenylphosphonium salts or 2-diphenylphosphine oxides with aldehydes and lactols affords good yields of the corresponding enol ethers. In selected examples these enol ether products may be further converted to spiroketals some of which are natural pheromones derived from $\text{Dacus oleae}$ and $\text{Paravespula vulgaris}$.