Muonium chemistry: kinetics of the gas phase reaction Mu + F2 → MuF + F from 300 to 400 K

The MSR (muonium spin rotation) technique was used to measure the chemical reaction rate for Mu + F₂ → MuF + F in N₂ moderator at ≈ 1 atm from 295 to 383 K giving the Arrhenius expression: log₁₀k (?/mole s) = (10.83 ± 0.20) - (200 ± 50)/T, with k = (1.46 ± 0.11) × 10¹⁰ ?/mole s at 300 K. This is at least 6.8 times the room temperature rate constant for the analogous H atom reaction. The measured activation energy and enhancement over the H reaction rate are indicative of significant tunnelling in the Mu reaction, in agreement with the recent collinear quantum mechanical calculations of Connor et al.     

The Electronic Structure of Vinyl Ethers and Sulfides with Interrupted Conjugation Examined by Photoelectron Spectroscopy

Photoelectron spectroscopy has been used to examine the consequences of steric inhibition of conjugation in a distorted vinyl sulfide and vinyl ether. Based upon the degree of interaction a deviation from coplanarity of 70°–75° is calculated for 9-oxabicyclo[3.3.1]non-1-ene ( 3 ) and approximately 75°–80° for the sulfur analog 6 .     

Conjugate additions of a simple monosilylcopper reagent with use of the CuI.DMS complex: stereoselectivities and a dramatic impact by DMS

Conjugate additions utilizing the simple monosilylcuprate reagent Li[PhMe2SiCuI] to alpha,beta-unsaturated carbonyl compounds are described. The presence of dimethyl sulfide (DMS), either as a component originating from the (CuI)4(DMS)3 complex or as a solvent added, has an amazing influence on both chemical yield and the level of diastereomeric ratio (dr) of the products. Gilman-type silylcyanocuprates {Li(Ph2MeSi)2Cu/LiCN} have previously been used to guarantee good results in conjugate addition reactions. External additives such as HMPA, tributylphosphine, or dialkylzinc are not necessary in conjunction with the simple Li[PhMe2SiCuI] reagent. It is demonstrated that the monosilylcuprate reagent with DMS as the solvent is very useful with sterically hindered (beta,beta-disubstituted) enones, and provides very high yields of the beta-silylated 1,4-addition products. Since there is no oligomerization problem associated with the simple monosilylcuprate reagent, this reagent should be considered as a very useful 1,4-silyl donor to enals, enones, and enoates in conjugate addition reactions.     

Strategies for hydrogen storage in metal--organic frameworks

Increased attention is being focused on metal-organic frameworks as candidates for hydrogen storage materials. This is a result of their many favorable attributes, such as high porosity, reproducible and facile syntheses, amenability to scale-up, and chemical modification for targeting desired properties. A discussion of several strategies aimed at improving hydrogen uptake in these materials is presented. These strategies include the optimization of pore size and adsorption energy by linker modification, impregnation, catenation, and the inclusion of open metal sites and lighter metals.     

Characterization of H2 binding sites in prototypical metal-organic frameworks by inelastic neutron scattering

The hindered rotor transitions of H(2) adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 were studied by inelastic neutron scattering to gain information on the specifics of H(2) binding in this class of adsorbents. Remarkably sharp and complex spectra of these materials signify a diversity of well-defined binding sites. Similarities in the spectral features as a function of H(2) loading and correlations with recent crystallographic studies were used to assign transitions ranging in rotational barrier from <0.04 to 0.6 kcal/mol as corresponding to localized adsorption sites on the organic and inorganic components of these frameworks. We find that binding of H(2) at the inorganic cluster sites is affected by the nature of the organic link and is strongest in IRMOF-11 in accord with our adsorption isotherm data. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H(2) loading, which demonstrates their importance for hydrogen uptake by these materials.     

Fabrication of polyelectrolyte multilayer films comprising nanoblended layers

Polyelectrolyte multilayer thin films were prepared via the alternate deposition of poly(allylamine hydrochloride) (PAH) and a blend of poly(acrylic acid) (PAA) and poly(styrenesulfonate) (PSS). When the pH of the blend solution was 3.5, the presence of PAA in this solution significantly increased the total film thickness. With only 10 wt % PAA in the blend adsorption solution, a large increase in film thickness was observed (92 nm cf. 18 nm). It was also demonstrated that the total amount of PSS adsorbed was enhanced by the presence of PAA in the blend solution, showing that the blend solution composition influenced that of the multilayer films. Thin films prepared with nanoblended layers also showed improved pH stability, because they exhibited reduced film rearrangement upon exposure to acidic conditions (pH = 2.5).     

Zur Kenntnis der RbNiCrF6Typs. III. Neue Fluoride des Typs CsZnMF6 mit M = Al,Ga, In,Tl, Sc,Ti, V,Mn, Cu,Rh

On the RbNiCrF₆ Type. III. New Fluorides of the Type CsZnMF₆ (M = Al, Ga, In, Tl, Sc, Ti, V, Mn, Cu, Rh) Cubic compounds are CsZnGaF₆ [3] (colourless, a = 10.29 Å); CsZnInF₆ (colourless, a = 10.58 Å); CsZnTlF₆ (colourless, a = 10.62 Å); CsZnScF₆ (colourless, a = 10.58 Å); CsZnTiF₆ (lightblue, a = 10.50 Å); CsZnVF₆ (lightgreen, a = 10.43 Å); CsZnMnF₆ (redbrown, a = 10.40 Å); CsZnCuF₆ (light brown, a = 10.24 Å); CsZnRhF₆ (redbrown, a = 10.41 Å), all RbNiCrF₆ type of structure, in addition non cubic: CsZnAlF₆ (colourless). The Madelung part of lattice energy, MAPLE, is calculated and discussed.     

Color Bricks: Building Highly Organized and Strongly Absorbing Multicomponent Arrays of Terpyridyl Perylenes on Metal Oxide Surfaces

Terpyridine‐substituted perylenes containing cyclic anhydrides in the peri position were synthesized. The anhydride group served as an anchor for assembly of the terpyridyl‐crowned chromophores as monomolecular layers on metal oxide surfaces. Further coordination with Zn²⁺ ions allowed for layer‐by‐layer formation of supramolecular assemblies of perylene imides on the solid substrates. With properly selected anchor and linker molecules it was possible to build high quality structures of greater than ten successive layers by a simple and straightforward procedure. The prepared films were stable and had a broad spectral coverage and high absorbance. To demonstrate their potential use, the synthesized dyes were employed in solid‐state dye‐sensitized solar cells, and electron injection from the perylene antennas to titanium dioxide was observed.