Dimeric ruthenium(II) complexes containing bridging carboxylato and aquo ligands. The crystal structure of μ-aquobis(μ-trifluoroacetato)bis[(η4-cycloocta-1,5-diene)(trifluoroacetato)ruthenium(II)]

Protonation of [Ru(μ³-C₃H₄R)₂(C₈H₁₂)] (R = H, Me; C₈H₁₂ = cycloocta-1,5-diene) with haloacetic acids gives the dimers [Ru₂(C₈H₁₂)₂(O₂CR′)₂(μ-O₂CR′)₂-(μ-OH₂)] (R′ = CF₃, CCl₃ and CH₂Cl), which are precursors for a range of monomeric and dimeric ruthenium carboxylate complexes. The complex [Ru₂(C₈H₁₂)₂-(O₂CCF₃)₂(μ-O₂CCF₃)₂(μ-OH₂)] has been characterized by X-ray analysis.     

MOLECULAR HYDROGEN PRODUCTION BY UROPORPHYRIN AND COPROPORPHYRIN: A MODEL FOR THE ORIGIN OF PHOTOSYNTHETIC FUNCTION

Abstract— Since life originated when the earth's atmosphere was still chemically reducing, the photooxidation of the prevalent reduced organic compounds and the emission of molecular hydrogen would have been a useful form of photosynthesis. If the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis, then uroporphyrin served an early photosynthetic function. In the present study, ethylenediamine tetraacetic acid was oxidized by photoexcited uroporphyrin and coproporphyrin to produce molecular hydrogen in aqueous solution in the presence of colloidal platinum catalyst. In the presence of methyl viologen, a one-electron carrier, the reaction is cyclic and hydrogen gas is produced at a constant rate. The evidence suggests that porphyrin radical intermediates rather than hydroporphyrin are active in the formation of molecular hydrogen. A coproporphyrin-polyvinyl alcohol-colloidal platinum polymer was used as a model for the evolving biological system for photosynthesis in which reactants are held in close proximity.     

Voltammaetric characterization of small platinum-iridium-based mercury film electrodes

A 25-μm diameter microelectrode is constructed from 80% platinum-20% iridium alloy. Mercury films and hemispheres are readily deposited by cathodic reduction of mercury(I) onto the electrode surface and are completely removed by anodic oxidation. The platinum-iridium surface, in contrast with a platinum surface, is not scarred by interaction with mercury. Steady-state reduction currents and sharp oxidation peaks are obtained for the determination of cadmium at the PtIr-based mercury film electrode. The voltammetric signals depend on the age of the film, and hence routine analytical applications will require further development.     

Interrogating HIV integrase for compounds that bind- a SAMPL challenge

Tremendous gains and novel methods are often developed when people are challenged to do something new or difficult. This process is enhanced when people compete against each other-this can be seen in sport as well as in science and technology (e.g. the space race). The SAMPL challenges, like the CASP challenges, aim to challenge modellers and software developers to develop new ways of looking at molecular interactions so the community as a whole can progress in the accurate prediction of these interactions. In order for this challenge to occur, data must be supplied so the prospective test can be done. We have supplied unpublished data related to a drug discovery program run several years ago on HIV integrase for the SAMPL4 challenge. This paper describes the methods used to obtain these data and the chemistry involved.     

Novel Copolymers of Styrene. Alkyl and Alkoxy Ring-Substituted 2-Phenyl-1,1-dicyanoethylenes

Novel copolymers of trisubstituted ethylene monomers, alkyl and alkoxy ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC₆H₄CH=C(CN)₂ (where R is 2-ethyl, 4-i-propyl, 4-butyl, 4-i-butyl, 4-t-butyl, 2-ethoxy, and 4-hexyloxy) and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 4-t-butyl (1.45) > 4-i-propyl (1.38) > 2-ethyl (1.37) > 4-hexyloxy (1.33) > 4-i-butyl (1.24) > 2-ethoxy (1.13) > 4-butyl (1.04). High T _g of the copolymers, in comparison with that of polystyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (1–10% wt.), which then decomposed in the 500–800°C range.     

Magnetic iron oxide nanopowders produced by CO2 laser evaporation

Magnetic iron oxide nanopowders were produced with the laser evaporation technique under normal process gas pressure. In addition, the generated particles were coated in situ with stearic acid and separated on magnets. The methods and the used laboratory setup are briefly described. Influences of essential process conditions, particularly the use of continuous and pulsed laser radiation as well as the properties of the process gas, were experimentally investigated. The produced nanopowders were analysed with TEM, XRD, and magnetic measurements and confirmed the in-principle suitability of the presented method.     

Kinetics and products of the reactions of selected diols with the OH radical

Using a relative rate method, rate constants have been measured at 296 ± 2 K for the gas‐phase reactions of OH radicals with 1,2‐butanediol, 2,3‐butanediol, 1,3‐butanediol, and 2‐methyl‐2,4‐pentanediol, with rate constants (in units of 10^?12 cm³ molecule^?1 s^?1) of 27.0 ± 5.6, 23.6 ± 6.3, 33.2 ± 6.8, and 27.7 ± 6.1, respectively, where the error limits include the estimated overall uncertainty of ±20% in the rate constant for the reference compound. Gas chromatographic analyses showed the formation of 1‐hydroxy‐2‐butanone from 1,2‐butanediol, 3‐hydroxy‐2‐butanone from 2,3‐butanediol, 1‐hydroxy‐3‐butanone from 1,3‐butanediol, and 4‐hydroxy‐4‐methyl‐2‐pentanone from 2‐methyl‐2,4‐pentanediol, with formation yields of 0.66 ± 0.11, 0.89 ± 0.09, 0.50 ± 0.09, and 0.47 ± 0.09, respectively, where the indicated errors are the estimated overall uncertainties. Pathways for the formation of these products are presented, together with a comparison of the measured and estimated rate constants and product yields. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 310–316, 2001