An alternative approach to 3-(diphenylphosphino)hexahelicene

3-(Diphenylphosphino)hexahelicene is synthesised in good yield and purity, via a three-step sequence involving a palladium-catalysed Mizoroki-Heck coupling reaction and classical oxidative photocyclisation. Mononuclear ruthenium and palladium complexes of 3-(diphenylphosphino)hexahelicene are prepared and characterised.     

Synthesis and X-ray structure of neutral Pd(IV) hydride complexes supported by β-ketoimine ligands

A series of neutral palladium(IV) hydride complexes supported by β-ketoimine ligands was synthesized. Reaction of dichlorobis(acetonitrile)palladium(II) with β-ketoamines (1–4) in dichloromethane at room temperature generated dark red solids of [PdCl₂(β-ketoimine)(H)] (6–9) in which the central carbon of the ketoimine ligand is σ-bound to the palladium. All the new complexes have been characterized by NMR and IR spectroscopy. The structure of complex(9) has been solved by X-ray crystallography.     

Dielectric spectroscopy study of the new compound [C<Subscript>12</Subscript>H<Subscript>17</Subscript>N<Subscript>2</Subscript>]<Subscript>2</Subscript>CdCl<Subscript>4</Subscript>

The temperature dependence of the electrical conductivity of the compound 2,4,4-trimethyl-4,5-dihydro-3H-benzo[b] [1,4] diazepin-1-ium tetrachlorocadmiate in the different phases follows the Arrhenius law. The imaginary part of the permittivity constant is analyzed with the Cole–Cole formalism. In the temperature range 348–394 K, the activation energy of conductivity obtained from complex permittivity in regions I and II are, respectively, 1.03 and 0.33 eV, and E _m (in regions I and II are, respectively, 0.97 and 0.36 eV) obtained from the modulus spectra is close, suggesting that the ion transport is probably due to a hopping mechanism. The Kohlrausch–Williams–Watts function, j(t) = exp( - ( \fractt_\textKWW )^b ) \varphi (t) = \exp \left( { - {{\left( {\frac{t}{{{\tau_{\text{KWW}}}}}} \right)}^\beta }} \right) , and the coupling model are utilized for analyzing electric modulus at various temperatures. The decreasing of β at 373 K is due to approaching the temperatures of change in the conduction mechanism of the sample.     

The design of an optimal viscous damper for a bridge stay cable using energy-based approach

An energy-based method is developed in the present paper to evaluate the damping property of a stay cable when transversely attached to a viscous damper. The overall increase of the cable damping offered by the external damper is determined by examining the time history of the kinetic energy in the damped cable. The concept of kinetic energy decay ratio is introduced as a key index to evaluate the effectiveness of a damper design in suppressing cable vibration. Compared to earlier studies, the proposed energy-based approach has no restrictions on the damper location. In addition, the flexural rigidity and sag extensibility of the cable are included in the formulation. Numerical simulation of free vibration of a damped stay cable is conducted using ABAQUS. To assist the design process, a set of damping estimation curves, which directly relate a damper design with the corresponding equivalent structural damping in a damped cable are developed for the practical parameter ranges of bridge stay cables. A number of numerical examples are presented. The validity and accuracy of the proposed method and damping estimation curves are verified by comparing with other studies. Results show that the energy-based approach developed in the present study is effective and efficient in determining the overall damping property of a cable-damper system, particularly in the preliminary stage of a damper design. In addition, the flexible applications of the developed damping estimation curves to damper design are demonstrated through these examples.     

Numerical and experimental analysis of the birefringence of large air fraction slightly unsymmetrical holey fibres

Careful numerical computations show that very slight geometrical imperfections of the cross-section of actual large air-fraction holey fibres (d/Λ > 0.6) may induce surprisingly high birefringence, corresponding to beat lengths as short as few millimeters. The spectral variations of this birefringence obeys laws similar to those of elliptical core Hi-Bi holey fibres with low air-fraction. For all the tested fibres, the group birefringence numerically deduced from the only shape birefringence is in good agreement with the measured one that does not varies when strongly heating the fibres. These computations and measurements show that the contribution of possible inner stress to the birefringence is negligible.     

Emissvity of metallic microcontoured surfaces

In this paper, we study the diffraction of electromagnetic radiation by a periodic micro-rough surface separating vacuum from a metal with a finite conductivity. We submit the integral method to the surface impedance boundary condition. Thus the numerical implementation is greatly reduced. We compare the numerical emissivities obtained by this approach to those we have calculated through the rigorous multilayer modal method. This enables us to show that the mentioned approximate method has two regions of validity: one corresponding to fairly flat surfaces and the other to very deep surfaces. It is well known that both the Kirchhoff approximation and the constant flat boundary impedance approximation are also valid for fairly flat surfaces. Our investigation aims also to establish whether these two approximate methods lead to the same results, and whether the integral method submitted to the surface impedance condition has a larger domain of validity. Concerning deep surfaces with a period smaller than the wavelength, we introduce the homogenization process in order to study its accuracy.Finally, this work permitted to identify three different regimes depending on the surface slopes: the simple scattering regime, the homogenization regime and the intermediate regime. For the latter, if the period is in the order of the wavelength, then we will show that the emissivity can be exalted.     

Synthesis,X-Ray Analysis,and Evaluation of the Optoelectronic Properties of a New Thia[6]helicene

The synthesis and structural characterization of a new hexahelicene derivative is reported. This compound features a new type of structure bearing a bromine atom. Suitable crystals of the latter indicate that its conformation closely resembles that of the unsubstituted [6]helicene, whose idealized symmetry is C2. The optoelectronic properties of this helical hexacyclic system were determined and exhibit a very interesting behavior.     

Synthesis,Electronic Properties and OLED Devices of Chromophores Based on λ5-Phosphinines

A new series of 2,4,6-triaryl-λ⁵-phosphinines have been synthesized that contain different substituents both on the carbon backbone and the phosphorus atom of the six-membered heterocycle. Their optical and redox properties were studied in detail, supported by in-depth theoretical calculations. The modularity of the synthetic strategy allowed the establishment of structure–property relationships for this class of compounds and an OLED based on a blue phosphinine emitter could be developed for the first time.     

Preparation and characterization of organic–inorganic hybrid compound [N(C<Subscript>4</Subscript>H<Subscript>9</Subscript>)<Subscript>4</Subscript>]<Subscript>2</Subscript>Cu<Subscript>2</Subscript>Cl<Subscript>6</Subscript>

Organic–inorganic hybrid sample [N(C₄H₉)₄]₂Cu₂Cl₆ was prepared via the reaction between copper chloride and tetrabutylammonium chloride. The compound was characterized by X-ray powder diffraction, IR, Raman, differential scanning calorimetry (DSC), DTA-TGA analysis and electrical impedance spectroscopy. DSC studies indicate a presence of one-phase transition at 343 K. The complex impedance of compound [N(C₄H₉)₄]₂Cu₂Cl₆ have been investigated in temperature and frequency ranges 300–380 K and 200 Hz–5 MHz, respectively. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination of bulk resistance R _p and constant phase elements CPE. The frequency dependence of the conductivity is interpreted in term of Jonscher's law: s(w) = s_dc + Awⁿ \sigma (\omega ){ } = {\sigma_{\rm{dc}}} + { }A{\omega^n} . The conductivity follows the Arrhenius relation. The variation of the value of these elements with temperatures confirmed the availability of the phase transition at 343 K detected by DSC and electrical measurements.     

Cohomology of Hom-Lie superalgebras and q-deformed Witt superalgebra

Hom-Lie algebra (superalgebra) structure appeared naturally in q-deformations, based on σ-derivations of Witt and Virasoro algebras (superalgebras). They are a twisted version of Lie algebras (superalgebras), obtained by deforming the Jacobi identity by a homomorphism. In this paper, we discuss the concept of α ^k -derivation, a representation theory, and provide a cohomology complex of Hom-Lie superalgebras. Moreover, we study central extensions. As application, we compute derivations and the second cohomology group of a twisted osp(1, 2) superalgebra and q-deformed Witt superalgebra.