Cleaner Continuous Photo‐Oxidation Using Singlet Oxygen in Supercritical Carbon Dioxide

High pressure under the spotlight : A new milliliter‐scale reactor is developed for using supercritical CO₂ to perform continuous photo‐oxidation reactions. Changing from a traditional microliter‐scale batch reaction to 8 hours of reaction using the new reactor gives a 3000‐fold scale‐up of the oxidation of α‐terpinene (see picture).

     

Hydroformylation by Pt-Sn compounds from N-heterocyclic stannylenes

[(Me(2)Si{NAr}(2))-κ(2)N,N']Sn, reacts with PtCl(2)(L(2)) and [PtCl(μ-Cl)(L)](2) to afford products containing Pt-Sn bonds. In the absence of supporting ligands L, coordination of the stannylene and rearrangement to a structurally unique PtSn(2)N(2)Si metallacycle occurs. The hydroformylation activity of a representative Pt-Sn compound is investigated.     

Electron spin resonance studies of the radiolysis of bi-π-cyclopentadienylalkyls of molybdenum and tungsten

Exposure of (C₅H₅)₂MO(CH₃)₂ and (C₅H₅)₂W(CH₃)₂, prepared from the corresponding dichlorides, to ²⁰Co γ-rays at 77 K gave H₂C.CML₃ carbene species characterised by their ESR spectra, together with a central feature possibly due to the parent cations. Dilute solutions in CD₃OD gave features assigned to the parent anions which were converted on bleaching with visible light into methyl radicals, and H₂C.ML₃ radicals. From the magnitude of the ¹H and ¹⁸³W hyperfine coupling constants, it is deduced that the SOMO for H₂C.WL₃ radicals is strongly localised on carbon.Dilute solutions in aqueous sulphuric acid also gave species with A(2H) = 20 G, identified as the carbene derivatives, H₂C.Ml₃. These were formed on annealing, as signals assigned to HSO₄ · radicals were lost.     

Some cubic curves associated with a triangle

There are many interesting cubic curves which arise from the geometry of the triangle. In particular, those which are invariant under the operation of isogonal conjugacy have attracted much attention, and a class of these is here investigated by a variety of methods.     

pH-dependent behavior of surface-immobilized artificial leucine zipper proteins

The coiled-coil protein motif occurs in over 200 proteins and has generated interest for a range of applications requiring surface immobilization of the constituent peptides. This paper describes an investigation of the environment-responsive behavior of a monolayer of surface-immobilized artificial proteins, which are known to assemble to form coiled-coil structures in bulk solution. An extended version of the quartz crystal microbalance (QCM-D) and surface plasmon resonance (SPR) are independently employed to characterize the adsorption of the proteins to a gold surface. The data suggest that the molecules arrange in a closely packed layer orientated perpendicular to the surface. QCM-D measurements are also employed to measure pH-induced changes in the resonant frequency (f) and the energy dissipation factor (D) of a gold-coated quartz crystal functionalized with the formed monolayer. Exposure of the protein monolayer to a pH 4.5 solution results in a shift of 43 Hz in f and a shift of -0.7 x 10(-6) in D as compared to pH 7.4. In contrast, increasing the pH to 11.2, results in f and D shifts of -17 Hz and 0.6 x 10(-6), respectively. The magnitude of the observed shifts suggests that the proteins form a rigid layer at low pH that can be hydrated to a fluid layer as the pH is increased. These observations correlate with spectroscopic changes that indicate a reduction in the helical content of the protein in bulk solutions of high pH.     

Paradigm confirmed: the first use of ionic liquids to dramatically influence the outcome of chemical reactions

It has been an unproven paradigm that the choice of which ionic liquid to use in a chemical reaction can have a dramatic effect on the outcome of that chemical reaction. We demonstrate, for the first time, that the reaction of toluene and nitric acid in three different ionic liquids gives rise to three completely different products in high yield. Furthermore, ionic liquids can catalyze these reactions with the only byproduct being water. [reaction: see text]     

A novel methodology for the synthesis of complexes containing long carbon chains linking metal centres: molecular structures of [Ru(dppe)Cp*]2(mu-C14) and [Co3(mu-dppm)(CO)7]2(mu3:mu3-C16)

Elimination of AuX(PR3)(X = halogen, R = Ph, tol) occurs readily in reactions between compounds containing C(sp)- or C(sp2)-X bonds and alkynyl or polyynyl gold(I) complexes; this reaction has been applied to the syntheses of complexes containing a variety of metal centres linked by C(n) chains (n up to 16).     

ESR spectra fo matrix-isolated bromobenzene cations formed by radiolysis

Exposure of dilute solution of bromobenzene and p-dibromobenzene in fluorotrichloromethane to ⁶⁰Co_γ-rays at 77 K gave the corresponding cations characterized by ESR spectra. Estimated spin densities on bromine of ≈ 30% and 23%, respectively, are greater than those predicted by comparison with neutral α-bromo radicals, R₂CBr (≈ 15%). Evidence for dimer cation formation in more concentrated solutions is presented.     

DDQ induced oxidative cyclisations of 1,2-dihydronaptho[2,1-b]furans

The DDQ mediated oxidative cyclisation reactions of a series of dihydronaptho[2,1-b]furans were examined. In the presence of an acid catalyst, the reaction yielded polycyclic ethers and lactones in good to excellent yields.     

Protein interactions with model chromatographic stationary phases constructed using self-assembled monolayers

Model surfaces representative of chromatographic stationary phases were developed by immobilising an homologous series (C2-C18) of n-alkylthiols, mixed monolayers of C4/C18 and thioalkanes with alcohol, carboxylic acid, amino and sulphonic acid terminal groups onto a flat, silver-coated glass surface using self-assembled monolayer (SAM) chemistry. The processes of adsorption and desorption of serum albumins onto the monolayer surfaces was monitored in real-time using surface plasmon resonance (SPR). Alkyl-terminated SAMs all showed a strong adsorption of bovine serum albumin which was largely independent of alkyl chain length, the ratio of mixed C4/C18 SAMs or the solution pH/ionic strength. The adsorption of human serum albumin to carboxylic and amine terminated SAMs was shown to be predominantly via non-electrostatic interactions (hydrophobic or hydrogen bonding). However, sulphonic acid terminated SAMs showed almost exclusively electrostatic interactions with human serum albumin. This preliminary work using self-assembled monolayer chemistry confirms the usefulness of well characterised SAMs surfaces for investigating protein adsorption and desorption onto/from model chromatography surfaces and gives some guidance for selecting appropriate functionalities to develop better surfaces for chromatography and electrophoresis.