Fabry Perot etalon with polymer cholesteric liquid-crystal mirrors

We present what we believe to be the first implementation of a Fabry-Perot (FP) etalon using polymer cholesteric liquid-crystal mirrors. These polymer mirrors have each been fabricated onto a single substrate, which allows the FP cavity spacing to be only a few micrometers wide. For the experimental results presented, cavity lengths of 13.8 and 7.6 mum yield near-infrared free spectral ranges of 24.8 and 45.6 nm, respectively. The measured finesse of 14.31 is approaching the limitation imposed by the reflectivity of the mirrors.     

Redox reactions involving rhenium and uranium hexafluorides,a convenient synthesis of β-uranium pentafluoride

Rhenium and uranium hexafluorides oxidise elemental iodine in iodine pentafluoride at ambient temperature to give the I₂⁺ cation. With UF₆ an additional reaction occurs to give β-uranium pentafluoride as one product, β-UF₅ is soluble in acetonitrile without disproportionation and is also formed from the reduction of UF₆ by MeCN. Copper, cadmium, and thallium metals are oxidised by ReF₆ in MeCN giving Cu^I, Cd^II, and Tl^I hexafluororhenates(V) but the reactions are complicated by reaction between ReF₆ and the solvent.     

The effect of alkene configuration on the partitioning between the carbenic reactions and the 1,7-electrocyclisation of α-)o-alkenylaryl)diazoalkanes

The 1,7-electroclyclisation of α-($\text{o}$-alkenylaryl)diazoalkenes to 1$\text{H}$-2,3-benzodiazepines is blocked by the $\text{cis}$ substituent in $\text{Z}$ alkenyl groups and the diazo-compounds then react via alternative routes including a new intramolecular carbene reaction to give naphtho[a]cycloheptenes.     

A technique for the indexed assessment of fumes generated by high-power laser processing

Information presented by other workers on fumes generated during high-power CO₂ laser processing tends in most cases to be empirical and qualitative in nature, which has limited the significance of this data to real industrial applications. This paper reviews information on the nature of laser processing fumes and proposes a model for indexing the risk associated with the fumes from both plastics and metal materials processing. The index allows the risks from a specific laser processing system to be assessed and classified into one of three groups. Classification of the risk associated with particular fumes enables appropriate choices about the extraction and filtration system to be made. Application of this model highlights the risks involved in processing stainless steel, owing to the formation of Cr(vi). It also highlights the problems associated with processing Kevlar, polycarbonate, and polyamide.     

A convergent approach to gamma-carbonyl vinyl boronates

Gamma-carbonyl vinyl boronates can be prepared by a visible light induced radical chain addition of an S-acyl dithiocarbonate (xanthate) to the pinacol ester of vinyl boronic acid, followed by treatment with base.     

Arsinophosphonium cations from arsenium-phosphine and -bisphosphine coordination chemistry

A new 14pi-electron tricyclic organoarsenium cation (5-hydrophenarsazinium, AN, C12H9AsN+) has been prepared in situ and used as a Lewis acceptor with trimethylphosphine, triphenylphosphine, bis(diphenylphosphino)methane (dppm), bis(dimethylphosphino)methane (dmpm), and 1,4-bis(diphenylphosphino)benzene (dppb) ligands. Solid-state structures and spectroscopic characterization data are reported for complexes of the general formula [AN-PMe3]+, [AN-PPh3]+, [AN-dppm]+, [AN-dppm-AN]2+, [AN-dmpm-AN]2+, and [AN-dppb-AN]2+ as tetrachlorogallate salts. Depending on reaction stoichiometry, dppm forms adducts at one or both of the donor sites. Structural comparisons with analogous complexes of phosphenium cations provide interesting similarities and differences.