Pyrroloquinolines,a New Platform for Developing Organic Photosensitizers: When Synthetic Methodology Meets Photophysics†

New molecular architectures with triplet sensitization properties can have a big impact on photochemistry and photobiology. In their recent work, de Bonfils et al. have tackled this challenge in a very systematic way using a powerful synthetic strategy. This consists of an elegant yet practical organocatalyzed cyclization/oxidation rearrangement sequence which they now apply to the synthesis of pyrroloquinolines, a new scaffold for photosensitizers. However, beyond this new class of compounds, the strategy has potential to produce a myriad of compact organic chromophores with promising photoinduced intersystem crossing properties. The study therefore provides interesting clues to serve the rational design of biocompatible molecular photosensitizers but also raises puzzling questions on the intriguing excited state reactivity of these molecular architectures.     

Spectral and oscillatory properties of a linear pencil of fourth-order differential operators

The paper deals with the spectral and oscillatory properties of a linear operator pencilA ? λB, where the coefficient A corresponds to the differential expression (py″)″ and the coefficient B corresponds to the differential expression ?y″ + cry. In particular, it is shown that all negative eigenvalues of the pencil are simple and, under some additional conditions, the number of zeros of the corresponding eigenfunctions is related to the serial number of the corresponding eigenvalue.     

Synthesis, crystal structure and optical investigation of the new phosphates: Na7Mg13Ln(PO4)12 (Ln=La, Eu)

Two new isostructural rare earth phosphates Na₇Mg₁₃Ln(PO₄)₁₂ (Ln=La, Eu) have been synthesized and investigated by X-ray diffraction and optical measurements. They crystallize in the orthorhombic system with the Cmc2₁ space group (Z=4). The crystal structure exhibits a new type of framework built up from LnO₈ (Ln=La, Eu), MO₆ (M=0.5Mg+0.5Na) and MgO_x (x=5, 6) polyhedra and PO₄ tetrahedra linked by common corner, edge or face. It can be described in terms of [Mg₄MP₄O₂₂]_∞ layers stacked along the a direction. These layers are interconnected by [Mg₄LnP₄O₃₆]_∞ undulating chains spreading along the b direction. This framework delimits 6 distinct cavities occupied by Na⁺ cations. The results of the optical study of Na₇Mg₁₃La_1−xEu_x(PO₄)₁₂ (x=0, 0.02, 0.1, 1) reveal the presence of two different Eu³⁺ ion environments whereas the X-ray study predicts the existence of only one Eu site. This difference can be explained by the possible presence of the europium element in the sodium sites with small occupancies which cannot be detected by the X-ray structural determination.     

Formulation fonction-courant et tourbillon du problème de Stokes dans un domaine bidimensionnel multiplement connexe

We consider the formulation of the Stokes problem in a multiply connected two-dimensional domain where the unknowns are the stream-function and the vorticity. We derive its equivalence with a finite system of several variational problems. This leads to the construction of a finite element discretization of this problem. The analysis and a numerical experiment prove the convergence of the method. To cite this article: M. Amara et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

Exact Solutions of Some Discrete Deconvolution Problems

In this work, we study the existence of solutions of the deconvolution problems in the discrete setting. More precisely, we prove the existence of solutions of the discrete multichannel deconvolution problems DMDP with convolvers being the characteristic functions of finite sets of positive integers. Also, we provide the reader with a simple method and a fast algorithm for finding the closed forms of the discrete deconvolvers with minimal supports that constitute exact solutions of the DMDP. Moreover, we show that unlike the singular value decomposition scheme, the multichannel deconvolution scheme based on the use of these discrete deconvolvers is not very sensitive to small 2-norm perturbation of the data. Finally, we show how to generalize our method for solving the 2-D version of the DMDP.     

Efficient capillary electrophoresis separation and determination of free amino acids in beer samples

Simultaneous detection of various o‐phthalaldehyde (OPA)‐labeled amino acids (AAs) in food samples was reported based on CE separation. Ionic liquid was used for the first time for CE analysis of AAs with in‐capillary derivatization. Several other additives, including SDS, α/β‐CD, and ACN, as well as key parameters for CE separation (buffer pH value, separation voltage), were also investigated. Our results show that the multiple additive strategy exhibits good stable and repeatable character for CE analysis of OPA‐labeled AAs, for either in‐capillary derivatization or CE separation, and allows simultaneous quantification of different OPA‐labeled AAs in a large concentration range of 50 μM to 3.0 mM with LOD down to 10 μM. Seventeen OPA‐labeled AAs, except for two pairs of AAs (His/Gln and Phe/Leu), which were separated with resolutions of 1.1 and 1.2, respectively, were baseline separated and identified within 23 min using the present multiple additive strategy. The method was successfully applied for simultaneous analysis of AAs in seven beer samples and as many as eleven trace‐amount AAs were detected and quantified, indicating the valuable potential application of the present method for food analysis.     

A competitive transport across polymeric membranes. Study of complexation and separation of ions

The removal and separation of Cu(II), Zn(II) and Ni(II) from nitrate aqueous solutions were studied by competitive transport across cellulose triacetate plasticized membranes modified with polyelectrolytes: polyethyleneimine (PEI) and polyethyleneglycol (PEG). Competitive transport of trace ions from aqueous solutions across polymer inclusion membranes containing a mixture of the three polymers (cellulose triacetate as the support) and tris(2-ethylhexyl-phosphate) (TEHP) as the plasticizer provide the selectivity order: Cu(II) > Ni(II) > Zn(II). A long-term transport experiment was carried out to demonstrate the durability of polymer inclusion membranes. A separation of bivalents cations (Cu²⁺, Ni²⁺, Zn²⁺) and monovalent cations (K⁺ and Na⁺) is achieved.     

Chlorpromazine Electro‐oxidation at BDD Electrode Modified with nZVI Nanoparticles Impregnated NiAl LDH

Nanocomposite of nanoscale zero‐valent iron (nZVI) and layered double hydroxide (LDH) was used as modifier for boron‐doped diamond electrode in determination of anti‐psychotic drug chlorpromazine (CPZ). nZVI nanoparticles were prepared by liquid phase reduction of ferric chloride with sodium borohydride on the surface of NiAl LDH matrix owing to the strong exchange and confinement efficiency of LDH. The structure, binding and surface properties of the nZVI@LDH nanocomposite were monitored using powder X‐ray diffractometry, FT‐IR spectroscopy, scanning and transmission microscopy and BET techniques. The electrochemical properties of the modified electrode were investigated by CV and EIS, performed in a phosphate buffer containing ferro/ferricyanide as redox probe. The modified electrode exhibited excellent electrochemical performance compared with unmodified electrode. As regard potential application of the nanocomposite surface to the CPZ detection, square‐wave voltammetric signals showed a good linear correlation over CPZ concentrations in a broad range from 0.1 to 8.0 μM with low detection limit of 0.005 μM. Nevertheless, these results suggest that the proposed nanocomposite modifier surface provides exceptional synergy and significant enhancement effect to the voltammetric response of CPZ and thus could be applied as highly efficient and stable platform of sensors in clinical analysis.