Synthesis and luminescence properties of cyclopalladated complexes with S^N and O^N donor ligands

The direct reaction between the hydroxo-complexes [{Pd(μ-OH)(C^N)}(2)] and protonated S^N-donor ligands to yield new dinuclear cyclometallated palladium(ii) complexes containing -NCS- bridging heterocyclic thionates of general formula [{Pd(μ-N^S)(C^N)}(2)] (C^N = 2-(2-pyridyl)phenyl (Phpy) I; = 7,8-benzoquinolyl (Bzq) II; N^S = pyrimidine-2-thionate (Spym) 1, benzoimidazolidine-2-thionate (Sbimid) 2, 1-methylimidazoline-2 thionate (Smeimid) 3) is described. The related mononuclear complexes [Pd(N^S)(C^N)] N^S = 2-aminothiophenolate (Atph) 4) were prepared in a similar way. Photophysical properties were investigated together with those of complexes with related ligands pyridin-2-thionate (Spy) 5 and pyrrole-2-carboxaldehydate (2-pcal) 6. All the compounds absorb intensely below 300 nm via(1)LC transitions located in Bzq or Phpy ligands, and display additional low energy absorptions of mixed (1)MLCT-(1)LC character. In the solid state diffuse reflectance UV-vis spectra, the differences are notable for dinuclear complexes. The complexes under study are quite unusual in terms of luminescence behaviour, since most of them are emissive in solution at room temperature and all display intense emissions in frozen CHCl(3) solution, but also in the solid state at 298 and 77 K. Emission quantum yields are in the range 2.52-0.14%, similar to that of related complexes. Structural characterisation by X-ray diffraction of complexes II3 and II6 confirmed the proposed formula.     

SYNTHESE DE SELS DE VINYLPHOSPHONIUMS β-SUBSTITUES ET DE SELS D'ALKYLPHOSPHONIUMS β-DISUBSTITUES

Abstract

Vinylene-1,2 bisphosphoniums salts react, in the presence of a base, with compounds ZH having a mobile hydrogen, to give a way of synthesis of β-substituted vinylphosphoniums salts 2 or β-disubstituted alkylphosphoniums salts 3. We have studied the limits of these synthesis depending on the experimental conditions and the nature of compounds ZH (alcohols, phenols, thiols, phosphines, amines).

Les sels de vinylène-1,2 bisphosphoniums réagissent, en présence d'une base, avec les composés à hydrogène mobile ZH pour fournir ainsi une méthode d'obtention de sels de vinylphosphoniums β-substitués 2 ou de sels d'alkylphosphoniums β-disubstitués 3. Nous avons étudié les limites de ces synthèses en faisant varier les conditions opératoires et la nature des composés ZH (alcools, phénols, thiols, phosphines, amines).     

Ultra lightweight PMMA-based composite plates with robust super-hydrophobic surfaces

Extremely lightweight plates made of an engineered PMMA-based composite material loaded with hollow glass micro-sized spheres, nano-sized silica particles and aluminum hydroxide prismatic micro-flakes were realized by cast molding. Their interesting bulk mechanical properties were combined to properly tailored surface topography compatible with the achievement of a superhydrophobic behavior after the deposition of a specifically designed hydrophobic coating. With this aim, we synthesized two different species of fluoromethacrylic polymers functionalized with methoxysilane anchoring groups to be covalently grafted onto the surface protruding inorganic fillers. By modulating the feed composition of the reacting monomers, it was possible to combine the hydrophobic character of the polymer with an high adhesion strength to the substrate and hence to maximize both the water contact angle (up to 157°) and the durability of the easy-to-clean effect (up to 2000 h long outdoor exposure).     

Screening of non-polar heterocyclic amines in urine by microextraction in packed sorbent-fluorimetric detection and confirmation by capillary liquid chromatography

A rapid and simple procedure for the direct screening of urine samples is described. The method involves microextraction in a packed sorbent (MEPS) that is on-line coupled to a capillary liquid chromatograph with fluorimetric detection. The overall arrangement works as a screening/confirmatory system for monitoring non-polar heterocyclic aromatic amines (HAAs) in urine samples. This configuration allows the selective retention of HAAs from urine on a C₁₈ MEPS cartridge integrated in the needle of a micro-well plate autosampler. Retained HAAs were eluted with methanol/water (90:10, v/v) and directly injected into the fluorimetric detector. This screening method provides a yes/no binary response that may require confirmation. The samples for which the concentration of HAAs was close to or above the established threshold limit (30 ng mL⁻¹) were subjected to capillary liquid chromatography (CLC) for confirmation purposes. A mobile phase of acetonitrile and triethylamine (25 mM) at pH 2.5, through a gradient of composition at a flow rate of 20 μL min⁻¹, resulted in good separations between the analytes in less than 11 min. This confirmation method allowed the determination of the analytes in the 10-100 ng mL⁻¹ range for harmane and norharmane and from 20 to 200 ng mL⁻¹ for 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b] indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido-[4,3-b] indole (Trp-P-2), 2-amino-9H-pyrido-[2,3-b] indole (AαC) and 2-amino-3-methyl-9H-pyrido-[2,3-b] indole (MeAαC), with relative standard deviation (RSD) values between 2.12% and 3.73%, and limits of detection between 1.6 and 5.6 ng mL⁻¹ for all the HAAs.     

Generative probabilistic models extend the scope of inferential structure determination

Conventional methods for protein structure determination from NMR data rely on the ad hoc combination of physical forcefields and experimental data, along with heuristic determination of free parameters such as weight of experimental data relative to a physical forcefield. Recently, a theoretically rigorous approach was developed which treats structure determination as a problem of Bayesian inference. In this case, the forcefields are brought in as a prior distribution in the form of a Boltzmann factor. Due to high computational cost, the approach has been only sparsely applied in practice. Here, we demonstrate that the use of generative probabilistic models instead of physical forcefields in the Bayesian formalism is not only conceptually attractive, but also improves precision and efficiency. Our results open new vistas for the use of sophisticated probabilistic models of biomolecular structure in structure determination from experimental data.     

Inertial Sensitivity of Porous Microstructures

Fluid flows through porous media are subject to different regimes, ranging from linear creeping flows to unsteady, chaotic turbulence. These different flow regimes at the pore scale have repercussions at larger scales, with the macroscale drag force experienced by a fluid moving through the medium becoming a nonlinear function of the average velocity beyond the creeping flow regime. Accurate prediction of the transition between different flow regimes is an important challenge with repercussions onto many engineering applications. Here, we are interested in the first deviation from Darcy’s law, when inertia effects become sizeable. Our goal is to define a Reynolds number, \(Re_{\mathrm{C}}\), so that the inertial deviation occurs when \(Re_{\mathrm{C}}\sim 1\) for any microstructure. The difficulty in doing so is to reduce the multiple length scales characterizing the geometry of the porous structure to a single length scale, \(\ell \). We analyze the problem using the method of volume averaging and identify a length scale in the form \(\ell =C_\lambda \sqrt{\nicefrac {K_\lambda }{\epsilon _\beta }}\), with \(C_\lambda \) a parameter that indicates the sensitivity of the microstructure to inertia. The main advantage of this definition is that an explicit formula for \(C_\lambda \) is given; \(C_\lambda \) is computed from a creeping flow simulation in the porous medium; and \(Re_{\mathrm{C}}\) can be used to predict the transition to a non-Darcian regime more accurately than by using Reynolds numbers based on alternative length scales. The theory is validated numerically with data from flow simulations for a variety of microstructures.