Polysulfonylamine. CLXVI [1] Kristallstrukturen von Metall‐di(methansulfonyl)amiden. 15 [1] Die isotypen Kristallstrukturen von Ammonium‐ und Caesium‐dimesylamid: Kristallographische Kongruenz zwischen Wasserstoffbrücken N—H···O/N und Metall‐Ligand‐Bindungen Cs—O/N

Polysulfonylamines. CLXVI. Crystal Structures of Metal Di(methanesulfonyl)amides. 15. The Isotypic Crystal Structures of Ammonium and Cesium Dimesylamide: Crystallographic Congruency of Hydrogen Bonds N—H···O/N and Metal‐Ligand Interactions Cs—O/N The ammonium salt NH₄[N(SO₂CH₃)₂] and its previously reported cesium analogue Cs[N(SO₂CH₃)₂] are isostructural (monoclinic, space group P2₁/n, Z = 4, V at —140 °C: 0.761 and 0.832 nm³ respectively). The cesium ion adopts an irregular (O₆N)‐heptacoordination by forming close contacts to one (O, N)‐chelating, one (O, O)‐chelating and three κ¹O‐bonding anions, whereas in the ammonium‐based structure each of the seven Cs—O/N interactions is perfectly mimicked by an N—H···O/N hydrogen‐bond component. To this effect, three N—H donors are engaged in asymmetric three‐centre bonds, the fourth in a moderately strong and approximately linear two‐centre bond. The crystal packings consist of anion monolayers that intercalate planar zigzag rows of cations propagating around symmetry centres (Cs···Cs alternatingly 422.5 and 487.5 pm, Cs···Cs···Cs 135.7°; N···N alternatingly 397.4 and 474.1 pm, N···N···N 136.1°). Each cation row is surrounded by and bonded to four translation‐generated anion stacks, and each anion stack connects two cation rows. The net effect is that the packings display congruent three‐dimensional networks of metal‐ligand bonds or hydrogen bonds, respectively. Moreover, close C—H···O/N interanion contacts consistent with weak hydrogen bonding are observed in both structures.     

Experimental demonstration of continuous variable quantum erasing

We experimentally demonstrate the concept of continuous variable quantum erasing. The amplitude quadrature of the signal state is labeled to another state via a quantum nondemolition interaction, leading to a large uncertainty in the determination of the phase quadrature due to the inextricable complementarity of the two observables. We show that by erasing the amplitude quadrature information we are able to recover the phase quadrature information of the signal state.     

High average power spectral beam combining of four fiber amplifiers to 8.2 kW

We report on the incoherent beam combination of the four narrow-linewidth fiber amplifier chains running at different wavelengths. Each main amplifier stage consists of a large-mode-area photonic crystal fiber delivering more than 2 kW of optical power. The four output beams are spectrally combined to a single beam with an output power of 8.2 kW using a polarization-independent dielectric reflective diffraction grating mainly preserving the beam quality of the individual fiber amplifiers.     

DFT calculations, DRIFT spectroscopy and kinetic studies on the hydrolysis of isocyanic acid on the TiO2-anatase (1 0 1) surface

The co-adsorption of isocyanic acid (HNCO) and water (H₂O) and their reaction to ammonia and carbon dioxide on the anatase phase of TiO₂ were studied with ab initio density functional theory (DFT) calculations using a cluster model as well as with in situ DRIFTS investigations and kinetic experiments. We found that isocyanic acid can in principle adsorb both molecularly and dissociatively on the TiO₂(1 0 1) surface, but the moment at which water gets involved in the process, is vital for determining the further course of the surface reaction. In the absence of water, it was found that HNCO can adsorb in molecular form on the TiO₂ surface. Assuming this case to be the first step of the HNCO hydrolysis, the surface HNCO rearranges into an intermediate complex with a modified NCO skeleton. After decarboxylation water attacks the complex from the gas phase and ammonia is finally formed.

However, when water is present at the beginning of the hydrolysis reaction, it immediately attacks the NCO group present at the surface, yielding a carbamic acid complex, which is further transformed into a carbamate complex. After decarboxylation an NH₂ group remains at the surface. Finally, NH₃ is formed by hydrogen transfer from molecularly adsorbed water at a neighboring titanium center and the hydrolysis reaction is completed.

Since water is always present in diesel exhaust gas, only the second mechanism is relevant under practical conditions. Moreover, the calculated energy barrier is lower for the second mechanism compared to the first reaction pathway. The comparison between the sum of the theoretical vibrational spectra of the reaction intermediates with the in situ DRIFT spectra also strongly supports the accuracy of the second reaction pathway. The experimental investigation of the kinetics of the HNCO hydrolysis on TiO₂-anatase revealed a second order reaction—first order with respect to HNCO and first order with respect to water, which can only be reconciled with the second mechanism.     

Copolymers derived from rapeseed derivatives via ADMET and thiol-ene addition

Novel (co)polymers were synthesized from substances obtained from rapeseed via ADMET and thiol-ene additions. α,ω-Dienes derived from oleic and erucic acid were copolymerized with a ferulic acid derivative, a representative phenolic acid (p-hydroxycinnamic acid) present, for instance, in rapeseed cake. Copolymers with different ratios of these monomers were prepared via two different routes (ADMET and thiol-ene) and studied in detail. Both monomer and polymer synthesis were optimized in order to achieve high yielding synthetic procedures that meet the requirements of green chemistry. Some thermal properties of the resulting copolymer series were then studied and correlated to the co-monomer composition.     

Tunnelling under a conical intersection: application to the product vibrational state distributions in the UV photodissociation of phenols

When phenol is photoexcited to its S(1) (1(1)ππ?) state at wavelengths in the range 257.403 ≤ λ(phot) ≤ 275.133 nm the O-H bond dissociates to yield an H atom and a phenoxyl co-product, with the available energy shared between translation and well characterised product vibration. It is accepted that dissociation is enabled by transfer to an S(2) (1(1)πσ?) state, for which the potential energy surface (PES) is repulsive in the O-H stretch coordinate, R(O-H). This S(2) PES is cut by the S(1) PES near R(O-H) = 1.2 ? and by the S(0) ground state PES near R(O-H) = 2.1 ?, to give two conical intersections (CIs). These have each been invoked-both in theoretical studies and in the interpretation of experimental vibrational activity-but with considerable controversy. This paper revisits the dynamic mechanisms that underlie the photodissociation of phenol and substituted phenols in the light of symmetry restrictions arising from torsional tunnelling degeneracy, which has been neglected hitherto. This places tighter symmetry constraints on the dynamics around the two CIs. The non-rigid molecular symmetry group G(4) necessitates vibronic interactions by a(2) modes to enable coupling at the inner, higher energy (S(1)/S(2)) CI, or by b(1) modes at the outer, lower energy (S(2)/S(0)) CI. The experimental data following excitation through many vibronic levels of the S(1) state of phenol and substituted phenols demonstrate the effective role of the ν(16a) (a(2)) ring torsional mode in enabling O-H bond fission. This requires tunnelling under the S(1)/S(2) CI, with a hindering barrier of ～5000 cm(-1) and with the associated geometric phase effect. Quantum dynamic calculations using new ab initio PESs provide quantitative justification for this conclusion. The fates of other excited S(1) modes are also rationalised, revealing both spectator modes and intramolecular vibrational redistribution between modes. A common feature in many cases is the observation of an extended, odd-number only, progression in product mode ν(16a) (i.e., the parent mode which enables S(1)/S(2) tunnelling), which we explain as a Franck-Condon consequence of a major change in the active vibration frequency. These comprehensive results serve to confirm the hypothesis that O-H fission following excitation to the S(1) state involves tunnelling under the S(1)/S(2) CI-in accord with conclusions reached from a recent correlation of the excited state lifetimes of phenol (and many substituted phenols) with the corresponding vertical energy gaps between their S(1) and S(2) PESs.