Diphosphines and pyrazole/pyrazolate-type ligands as building blocks in luminescent Au(I) complexes

A series of gold(I) complexes containing diphenylphosphine bridging ligands, dppm, dppe, dpephos, dbfphos and biphep and co-ligands of the type pyrazole have been synthesized. The X-ray crystal structures of [Au₂(μ-dpephos)(μ-pz^2CH3)][PF₆], [Au₂(μ-dbfphos)(μ-pz^2CH3)][PF₆], and of the starting compound [Au₂Cl₂(μ-biphep)] indicate that the structural and stoichiometric characteristics of the new complexes depend on the diphosphine ligand. The three complexes show Au?Au contacts between 3.27 Å and 3.30 Å, with that of the biphep compound being the shortest. Digold (I)-diphosphine derivatives with a bridging pyrazolate ligand are obtained in all cases, except when [Au₂Cl₂(μ-biphep)] is used as starting material. Surprisingly, in this case, two monodentate neutral pyrazole ligands are attached to the gold atoms. The new complexes are luminescent in the solid state at 77 K and in solution both at room temperature and 77 K. Low energy emission bands related to the presence of Au?Au interactions have been identified in some of the compounds in the solid state and/or in solution.     

Design of equalized holographic ROADMs for application in CWDM METRO networks

In this paper a design for an equalized holographic ROADM (Reconfigurable Optical Add-Drop Multiplexer) is done. This device can address several wavelengths at the input to different output fibers, according to the holograms stored in a SLM (Spatial Light Modulator), where all the outputs are equalized in power. All combinations of the input wavelengths are possible at the different output fibers.These type of ROADMs are designed for application in CWDM (Coarse Wavelength Division Multiplexing) networks, where the distance between the different wavelength allow the use of DML (Direct Modulation Lasers) without cooling, reducing the cost and the tolerances of the network components. Application in METRO networks and its interconnection with some PON (Passive Optical Network), as a part of the access to the subscriber, is reviewed.     

Effects of notches on the surface pressure field downstream of a wall-mounted spoiler

Notched spoilers have been observed to be more effective than uniform spoilers to suppress the flow-induced cavity resonance of vehicles with open sunroofs. In this study, a few mechanisms possibly involved in buffeting suppression from notched spoilers were investigated experimentally and numerically. One objective was to investigate the spatial coherence and phase of the wall pressure fluctuations downstream of notched spoilers in comparison with the same quantities for uniform spoilers. Another objective was to gather detailed measured data to allow the verification of computer simulations of the flow over the notched spoiler. Experiments were performed to measure the velocity and wall pressure fields downstream of spoilers mounted on the rigid floor of a closed test section wind tunnel. Efforts were made to reproduce the spoiler and wind tunnel geometry and boundary conditions of the experimental setup in the numerical simulations. The numerical investigation used the Lattice Boltzmann Method (LBM), with the so-called Very Large Eddy Simulation (VLES) viscosity turbulence model. The results of the numerical investigation were in satisfactory agreement with measured data at low frequencies, where buffeting is expected to occur. The results suggested that the notches break down the homogeneity of the leading edge cross-stream vortices predominantly responsible for the cavity excitation. This decreased the cross-stream coherence of the surface pressure field, thereby reducing the magnitude of the net equivalent excitation force acting over the surface downstream.     

An integer programming dynamic farm-household model to evaluate the impact of agricultural policy reforms on farm investment behaviour

We develop a multi-objective farm-household dynamic integer programming model to simulate investment behaviour in different policy and price scenarios, with a particular focus on the decoupling of the Common Agricultural Policy (CAP). The model takes into account the characteristics of individual assets, including ageing and fixity through the explicit consideration of transaction costs. A case study application in the context of arable farming in Northern Italy is provided as an example. The results emphasise different patterns of reaction of different farm-household types over time, as an effect of the varying opportunity costs of resources and initial asset endowments. Overall, this application highlights the potentialities and limits of the methodology. In particular, the approach proved to be effective in providing a variety of results depending on the individual features of each farm-household, such as the differences between: (a) a ‘no reaction’ attitude; (b) an adaptation of farm activity and assets; and (c) a radical reaction pattern guided by high-income alternatives to farming. This highlights the potential of this tool as a generator of ideas and working hypotheses. We argue that, in view of the further developments of the CAP, the use of instruments able to account for multiple objectives, dynamics and investment choices will become even more relevant in the analysis of EU agricultural policy.     

Performance evaluation of 100 and 200-Gb/s WDM PM-QPSK transmission systems: tolerance analysis to the optical link impairments according to the optical carrier shape

Polarization-multiplexing quadrature phase shift keying (PM-QPSK) has become a key ingredient in the design of 100 and 200-Gb/s dense wavelength-division multiplexed (DWDM) networks. The performance of the system using these formats varies according to the shape of the pulses employed by the optical carrier: non-return to zero (NRZ), return to zero (RZ) or carrier-suppressed return to zero (CSRZ). In this paper, we analyse the tolerance of PM-QPSK to linear and nonlinear optical impairments, including amplified spontaneous emission (ASE) noise, crosstalk, distortion by optical filtering, chromatic dispersion (CD), polarization mode dispersion (PMD) and fibre Kerr nonlinearities. The simulation results show that RZ formats with a low-duty cycle have a higher tolerance to CD, PMD and intrachannel nonlinearities due to the reduction of pulse-to-pulse interaction. Conversely, the PM–NRZ-QPSK format has a higher spectral efficiency (SE) than other options and shows better tolerance to filtering distortion and CD in filterless networks.     

Pure hydrogen production from methylcyclohexane using a new high performance membrane reactor

A high efficiency membrane reactor (Pd based) has been developed for hydrogen generation from methylcyclohexane, which is able to produce a pure hydrogen stream with a reaction yield close to 100%.     

The 3,5-dimethyl-4-nitropyrazole ligand in the construction of supramolecular networks of silver(I) complexes

Three new ionic silver complexes based on the 3,5-dimethyl-4-nitropyrazole ligand (Hpz^NO₂) and 1:2 or 1:3 (Ag:Hpz^NO₂) stoichiometries, [Ag(Hpz^NO₂)₂][BF₄], [Ag(Hpz^NO₂)₃][SbF₆] and [Ag(Hpz^NO₂)₃][PO₂F₂]·Hpz^NO₂ have been prepared and structurally characterised. The linear or trigonal metallic coordination environment, the NO₂ groups on the pyrazole ligand as well as the presence of counteranions of the type as , or (the latter one evolving to ) were strategically selected to produce molecular assemblies established on the basis of hydrogen-bonds (N-H?X) and π?π or coordinative interactions involving the NO₂ group. The complex [Ag(Hpz^NO₂)₂][BF₄] exhibited polymeric N-H?F hydrogen-bonded chains which were assembled in a 3D network by weaker coordinative Ag?O(NO₂) and π(NO₂)?π(NO₂) interactions. In the complex [Ag(Hpz^NO₂)₃][SbF₆], consistent with the three-coordinated molecular environment, the interactions were extended to give rise an open 3D cationic sub-network in which the counteranions were encapsulated. By contrast, in the related complex [Ag(Hpz^NO₂)₃][PO₂F₂]·Hpz^NO₂ the presence of a fourth non-coordinated pyrazole Hpz^NO₂ avoided the formation of a 3D network giving rise to a double-chained 1D structure.     

Luminescence of neutral and ionic gold(I) complexes containing pyrazole or pyrazolate-type ligands

A series of pyrazole (Hpz) and pyrazolate (pz⁻) Au(I) complexes of types [Au(Hpz^2R(n))(PPh₃)]⁺ (I), [Au(Hpz^2R(n))₂]⁺ (II), [Au(μ-pz^R(n))]₃ (III), [Au(pz^R(n)/2R(n))(PPh₃)] (IV), [AuCl(Hpz^R(n)/2R(n))] (V) and [(PPh₃)Au(μ-pz^R(n))Au(PPh₃)]⁺ (VI), R(n) and 2R(n) represent C₆H₄OC_nH_2n+1 substituents at the 3- or 3- and 5-positions of the heterocyclic ring, respectively, have been shown to be luminescent in the solid state at 77 K, independently of the presence or not of inter-metallic Au-Au interactions. The emission spectra of all complexes consist of structured bands in the region 395-500 nm, attributed to ligand-to-metal charge transfer (LMCT) transitions involving the Hpz or pz⁻ ligands, the pattern of bands of compounds being related with the molecular structure and/or the nature of the ligands. The thermal behaviour of several complexes of the types III, IV and V containing long-chain substituents (n ? 12) was examined by polarising light optical microscopy (POM). The derivative [AuCl(Hpz^R(12))] was proved to have liquid crystal properties exhibiting a mesophase SmA but the remaining complexes were not liquid crystal materials. This complex is one of the scarce examples of Au(I) derivatives exhibiting both liquid crystal and luminescent properties.