A (bpy)2Ru-coordinated dehydro[12]annulene with exotopically fused diimine binding sites

Synthesis and electronic properties of a dinuclear (bpy)(2)Ru(II) polypyridyl complex are described in which the bridging ligand consists of two dipyridophenazines fused to a formally antiaromatic dehydro[12]annulene and where the electronic and electrochemical properties of the complex are markedly influenced by the cyclic all-carbon core.     

Measurements of hyperon semileptonic decays at the CERN Super Proton Synchrotron

The charged hyperon beam at the CERN Super Proton Synchrotron (SPS) has been used to collect data on semileptonic decays ofΣ ^?,Ξ ^? andΛ. A magnetic channel selects 100 GeV/c negatively charged particles produced in the forward direction by interaction of the 200 GeV/c SPS proton beam on a BeO target. TheΣ ^? andΞ ^? hyperons are concurrently identified in a DISC ?erenkov counter, and their decay products are analysed by a magnetic spectrometer. Electron-hadron discrimination is achieved by the combined use of lead-glass and lead/scintillator counters, transition radiation detectors, and a ?erenkov counter. In this article we report results on the \(\Sigma ^ - \to \Lambda e^ - \bar v\) decay mode. Measurements of the Λ polarization and of the centre-of-mass distributions (baryon kinetic energy, electron-neutrino correlation, and Dalitz plot distributions) yield the vector to axialvector form factor ratiof ₁/g ₁=+0.034±0.080, in agreement with the value expected from the conserved vector current hypothesis (f ₁/g ₁=0). TheΣ ^?→Λe ^? v→ branching ratio measurement gives a value of (5.41±0.30)×10^?5. The effects of radiative corrections are not included in these results. They are discussed in the text. Results on the otherΞ ^?,Σ ^?, andΛ semileptonic decays are reported in separate articles.     

Electron correlation as the driving force for charge transfer: charge migration following ionization in N-methyl acetamide

A hole charge created in a molecule, for instance, by ionization, can migrate through the system solely driven by electron correlation. The migration of a hole charge following ionization in N-methyl acetamide (a molecular system containing a peptide bond) is investigated. The initial hole charge is localized at one specific site of the molecule. Ab initio calculations show that nearly 90% of the hole migrates to a remote site of the molecule in 4.2 fs. This migration of charge is highly efficient and ultrafast. The underlying mechanism for this migration of a hole charge is identified and compared with a simple model.     

Temperature dependence of the reaction C2H (C2D) + O2 between 295 and 700 K

The rate coefficients for the reactions of C₂H and C₂D with O₂ have been measured in the temperature range 295 K T 700 K. Both reactions show a slightly negative temperature dependence in this temperature range, with k_C2H+O2 = (3.15 ± 0.04) × 10⁻¹¹ (T/295 K)^{−(0.16 ± 0.02)} cm³ molecule⁻¹ s⁻¹. The kinetic isotope effect is k_C2H/k_C2D = 1.04 ± 0.03 and is constant with temperature to within experimental error. The temperature dependence and the C₂H + O₂ kinetic isotope effect are consistent with a capture-limited metathesis reaction, and suggest that formation of the initial HCCOO adduct is rate-limiting.     

N‐Heterocyclic Silylenes in Boron Chemistry: Facile Formation of Silylboranes and Silaborinines

Reaction of a N‐heterocyclic silylene (NHSi) with PhBX₂ (X=Cl, Br) readily afforded six‐membered silaborinines through an insertion/ring expansion sequence. Increasing the sterics of the borane from phenyl to duryl enabled the selective generation and isolation of the highly colored silylborane intermediates. Theoretical studies on the mechanism and energetics of the silaborinine formation were fully consistent with the experimental observations.