Reaction with hydrazonoyl halides XXIII [1]: Synthesis and reactions of C‐coumarinoyl‐N‐arylformohydrazonoyl bromides

C‐Coumarinoyl‐N‐arylformohydrazonoyl bromides ( 3 ) were synthesized by reaction of N‐nitrosoarylacetamides with an appropriate sulfonium bromide in ethanol at room temperature. The reactions of potassium thiocyanate, potassium selenocyanate, thiourea, methyl phenylthiocarbomate, and methyl phenylhydrazinedithioate with hydrazonoyl bromide 3a were examined. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 355–362, 1999     

Magnetic exchange coupling in imido bimetallic uranium(V) complexes. A relativistic DFT study

Magnetic exchange coupling between uranium U(V) ions, in the case of the two para- and meta-imido diuranium complexes, respectively [(C₅H₅)₃U]₂(μ-1,4-N₂C₆H₄) and [(C₅H₅)₃U]₂(μ-1,3-N₂C₆H₄) exhibiting the 5f¹-5f¹ configuration, have been investigated using relativistic DFT calculations, combined with the broken symmetry (BS) approach. Using the B3LYP functional, the singlet BS state of the para complex has been found of lower energy than the high spin (HS) triplet one, in agreement with the observed antiferromagnetic character of the complex. On the contrary the BP86 functional fails to predict this magnetic property. The spin density distributions and MO analysis explain well the antiferromagnetic character of the para complex and clarify the failure of the BP86 functional. The effective participation of the 5f metal orbitals in bonding with the imido ligand plays a key role for electronic and magnetic communication between the two active U(V) 5f¹ electrons. The same technique led us to explain the ferromagnetic character of the meta isomer in agreement with experiment. For both isomers the spin polarization mechanism explains well their observed magnetic behaviour.     

A relativistic DFT study of magnetic exchange coupling in ketimide bimetallic uranium(IV) complexes

Magnetic exchange couplings in bis(ketimide) binuclear U^IV/U^IV complexes [Cp′₂UCl]₂(μ-ketimide) diuranium(IV) and [(C₅H₅)₂(Cl)An]₂(μ-ketimide) (Cp′ = C₅Me₄Et; ketimide = N=CMe-(C₆H₄)-MeC=N) have been investigated computationally using relativistic density functional theory (DFT) combined with the broken symmetry (BS) approach. Using the B3LYP hybrid functional, the BS ground state of these U^IV/U^IV 5f ²–5f ² complexes has been found of lower energy than the high spin (HS) quintet state, indicating an antiferromagnetic character (estimated coupling constant |J| < 5 cm⁻¹) which has not yet been evidenced unambiguously experimentally. On the contrary, the BP86 GGA functional overestimates greatly the antiferromagnetic character of the complexes (|J| > 100 cm⁻¹). As recently reported for para-bis(imido) [(C₅H₅)₃U]₂(μ-imido) uranium(V) complex, spin polarization is mainly responsible for the antiferromagnetic coupling through the π-network orbital pathway within the bis(ketimide) bridge. Furthermore, spin polarization is exalted by the combined roles of the 5f metal orbitals and of the π-conjugated ketimide bridging ligand which permit electronic communication between the two uranium atoms albeit separated by a distance of the order of 10 ?. The MO analysis clarifies which MOs contribute to the antiferromagnetic coupling in the binuclear complexes under consideration and brings to light the 5f orbitals driving contribution.     

On completely integrable coupled Burgers and coupled Korteweg–de Vries systems

In this work, we study two completely integrable equations, namely, coupled Burgers and Korteweg–de Vries systems. The modified form of Hirota’s bilinear method, established by Hereman, is employed to formally derive multiple-soliton solutions and multiple-singular-soliton solutions for each system. Hirota’s bilinear method is reliable and effective and can also be applied to solve other types of higher-dimensional integrable and non-integrable systems.     

Circular grating waveguide structures for intracavity generation of azimuthal polarization in a thin-disk laser

We report on the generation of beams with azimuthal polarization using resonant grating waveguide structures (GWSs) inside an Yb:YAG thin-disk laser (TDL) oscillator. Two different GWS concepts were used to select the polarization of the emitted beam. The first uses the resonant reflection principle, and the second is based on the leaky-mode approach already reported in our previous work. Up to 93 W and 103 W of output power were extracted from a TDL with an optical efficiency, η(oo), of 36.2% and 40.1% using the first and the second approaches, respectively. In both cases, a pure azimuthal polarization and a beam quality factor, M2, of about 2.2 were measured. The design, fabrication, and different experimental results, as well as the laser performances for both GWSs, are discussed in the present Letter.     

Continuous-wave Yb-doped Sc2SiO5 thin-disk laser

We present in this Letter experimental results of a Yb:Sc(2)SiO(5) (Yb:SSO) thin-disk laser. To our knowledge, this is the first lasing demonstration of this crystal in thin-disk configuration reported on to date. Preliminary tests regarding the characterization and the laser operation are presented. Two different resonator configurations, a simple linear multimode cavity, and a fundamental-mode folded resonator providing a double pass in the laser crystal were set up. The gain and the small signal gain of the available Yb:SSO sample were calculated using the experimental results of the multimode resonator. The operation in a fundamental-mode resonator with the double pass in the laser crystal led to 9.4 W of output power with an optical efficiency of 25.4%.     

Structural Diversity Within the Series of 68-Electron M4L n E2 (L = 2-Electron Ligand; M = Fe, Ru, Os, Co; E = CH, N, P, NR, PR, S) Organometallic Clusters: A Theoretical Investigation

Four different skeletal structural arrangements with very different connectivities are known for 6-vertex/68-electron of M₄E₂ core (M = transition metal; E = main-group atom or ligand). DFT calculations on a large number of title model compounds allow to rationalize the preferences between these structural shapes with respect to the nature of the metal and main-group elements constituting the cluster cage. In particular, the electronegativity of M and the “size” (first-row vs. second-row element) of E play an important role in the stability preference of a particular isomer. For several compounds, although only one type of structure is known, other low-energy isomeric forms are also likely to exist. Moreover, two structural types, so far unreported, are predicted to be stable enough for being synthesized.     

Further improved F-expansion and new exact solutions for nonlinear evolution equations

The improved F-expansion method with a computerized symbolic computation is used to construct the exact traveling wave solutions of four nonlinear evolution equations in physics. As a result, many exact traveling wave solutions are obtained which include new soliton-like solutions, trigonometric function solutions, and rational solutions. The method is straightforward and concise, and it holds promise for many applications.     

A generalized auxiliary equation method and its applications

In this paper, a generalized auxiliary equation method with the aid of the computer symbolic computation system Maple is proposed to construct more exact solutions of nonlinear evolution equations, namely, the higher-order nonlinear Schrödinger equation, the Whitham–Broer–Kaup system, and the generalized Zakharov equations. As a result, some new types of exact travelling wave solutions are obtained, including soliton-like solutions, trigonometric function solutions, exponential solutions, and rational solutions. The method is straightforward and concise, and its applications are promising.     

New explicit and exact traveling wave solutions for two nonlinear evolution equations

In this paper, with the aid of computer symbolic computation system such as Maple, an algebraic method is firstly applied to two nonlinear evolution equations, namely, nonlinear Schrodinger equation and Pochhammer–Chree (PC) equation. As a consequence, some new types of exact traveling wave solutions are obtained, which include bell and kink profile solitary wave solutions, triangular periodic wave solutions, and singular solutions. The method is straightforward and concise, and it can also be applied to other nonlinear evolution equations in mathematical physics.