NOUVEAUX DÉCONTAMINANTS. ACTION DU MONOPERPHTALATE DE MAGNÉSIUM (MPPM) SUR QUELQUES INSECTICIDES ET TOXIQUES DE GUERRE ORGANOPHOSPHORÉES OU ORGANOSOUFRÉS

Abstract

Magnesium monoperoxyphthalate (MMPP) is a good decontaminant reagent when it is used in alcoholic solvent. Paraoxon (O,O-diethyl O-paranitrophenyl phosphate) but specially VX [O-ethyl S-(2-diiso-propylaminoethyl)] methylphosphonothiolate and HD (2,2′-dichlorodiethyIsulfide) react with MMPP completely in a very short time.

Le monoperphtalate de magnesium (MPPM) est un bon agent de décontamination lorsqu'il est utilisé en milieu alcoolique. Le Paraoxon (O.O-diéthyl O-paranitrophenyl phosphate) mais surtout le VX [O-éthyl S-(diisopropylaminoéthyl-2)] méthylphosphonothiolate et l'ypérite (HD) (dichloro-2.2′diéthyl-sulfure) réagissent de faFon totale avec le MPPM en un temps très court.     

Synthesis of (2-Furyl)Aminomethanephosphonic Acids Derivatives

Abstract

Synthetical aspects of furylaminophosphonic acids are discussed here.     

Bis­[(R)‐1‐phenyl­ethyl isocyanido](5,10,15,20‐tetrakis{2,6‐bis[(S)‐2,2‐di­methyl‐1,3‐dioxolan‐4‐yl­methyl­oxy]­phenyl}­porphyrin)­ruthenium(II) at 110 K

The geometry about the Ru atom in the title compound, [Ru(C₉H₉N)₂(C₉₂H₁₀₈N₄O₂₄)], is approximately tetragonal and the porphyrin ring is nearly planar, while the C—N—R angles [169.3 (3) and 163.9 (3)°] of the isocyanide ligands in the complex are different from the value of 180° expected in the free ligand.     

Spectroscopic characterization of a high-potential lipo-cupredoxin found in Streptomyces coelicolor

For many streptomycetes, a distinct dependence on the "bioavailability" of copper ions for their morphological development has been reported. Analysis of the Streptomyces coelicolor genome reveals a number of gene products encoding for putative copper-binding proteins. One of these appears as an unusual copper-binding protein with a lipoprotein signal sequence and a cupredoxin-like domain harboring a putative Type-1 copper-binding motif. Cloning of this gene from S. coelicolor and subsequent heterologous expression in Escherichia coli has allowed for a thorough spectroscopic interrogation of this putative copper-binding protein. Optical and electron paramagnetic resonance spectroscopies have confirmed the presence of a "classic" Type-1 copper site with the axial ligand to the copper a methionine. Paramagnetic NMR spectroscopy on both the native Cu(II) form and Co(II)-substituted protein has yielded active-site structural information, which on comparison with that of other cupredoxin active sites reveals metal-ligand interactions most similar to the "classic" Type-1 copper site found in the amicyanin family of cupredoxins. Despite this high structural similarity, the Cu(II)/(I) midpoint potential of the S. coelicolor protein is an unprecedented +605 mV vs normal hydrogen electrode at neutral pH (amicyanin approximately +250 mV), with no active-site protonation of the N-terminal His ligand observed. Suggestions for the physiological role/function of this high-potential cupredoxin are discussed.     

Ionic core-shell dendrimers with an octacationic core as noncovalent supports for homogeneous catalysts

Ionic core-shell dendrimers with an octacationic core have been applied as noncovalent supports for homogeneous catalysts. Catalytically active arylpalladium complexes, which bear a tethered sulfato group, were noncovalently attached to the ionic core-shell dendritic supports via a straightforward ion-exchange reaction under mild conditions. Diagnostic shifts in (1)H NMR and Overhauser contacts show that the sulfato groups of the catalysts are located close to the octacationic core of the dendritic support in the resulting assemblies. The location of the catalytic Pd(II) sites has been varied via two strategies: by increasing the dendrimer generation and/or by shortening of the sulfato tether. In addition, a metallodendritic assembly was prepared, which bears an alternative shell of apolar dodecyl groups. Both the dendrimer size and the nature of the dendritic shell have no influence on the binding properties of the dendritic supports, i.e., the octacationic dendrimers of generations 1-3 form discrete 1:8 assemblies with the arylpalladium complexes. The structural aspects and the nature of the metallodendritic assemblies have been studied by means of pulse gradient spin-echo NMR diffusion methods, Overhauser spectroscopy, and electron microscopy (TEM). These techniques showed that the dendritic supports and arylpalladium complexes are strongly associated in solution to give unimolecular assemblies of nanoscopic dimensions. Membrane dialysis can recover these metallodendritic assemblies due to their nanoscopic size. The catalytic performances of the metallodendritic assemblies are comparable, but slightly lower than the performance of the unsupported catalyst.     

Hydroxy- and mercaptopyridine pincer platinum and palladium complexes generated by silver-free halide abstraction

A silver-free route has been employed for the synthesis of a number of Pd and Pt complexes supported by an NCN "pincer" ligand (NCN = [2,6-(Me2NCH2)2C6H3]-) via halide abstraction. This was achieved by the use of o-, m-, and p-hydroxypyridines or o- and p-mercaptopyridines in basic ethanol solutions. The acidic OH or SH protons are removed to generate the formally anionic ligands. X-ray crystal structure determination of these complexes shows that the bonding of the substituted pyridine ligands occurs exclusively through the pyridine N for hydroxypyridines and exclusively through the thiol S in mercaptopyridines. In the hydroxypyridine case, the ortho and para isomers tautomerize to generate pyridone structures with a covalent M-N bond, whereas the m-hydroxypyridine complex, which is unable to tautomerize, is found to still be bound through the pyridine N but in a zwitterionic structure. The mercaptopyridine complexes are the first reported examples of pincer-ligated Pd and Pt thiolate species. The pyridine ligands can be quantitatively exchanged for chloride by reaction with excess NH4Cl, a potentially useful chemical switch for ligation/decomplexation of this ligand type.     

A novel heteroditopic terpyridine-pincer ligand as building block for mono- and heterometallic Pd(II) and Ru(II) complexes

A palladium-catalyzed Stille coupling reaction was employed as a versatile method for the synthesis of a novel terpyridine-pincer (3, TPBr) bridging ligand, 4'-{4-BrC6H2(CH2NMe2)2-3,5}-2,2':6',2' '-terpyridine. Mononuclear species [PdX(TP)] (X = Br, Cl), [Ru(TPBr)(tpy)](PF6)2, and [Ru(TPBr)2](PF6)2, synthesized by selective metalation of the NCNBr-pincer moiety or complexation of the terpyridine of the bifunctional ligand TPBr, were used as building blocks for the preparation of heterodi- and trimetallic complexes [Ru(TPPdCl)(tpy)](PF6)2 (7) and [Ru(TPPdCl)2](PF6)2 (8). The molecular structures in the solid state of [PdBr(TP)] (4a) and [Ru(TPBr)2](PF6)2 (6) have been determined by single-crystal X-ray analysis. Electrochemical behavior and photophysical properties of the mono- and heterometallic complexes are described. All the above di- and trimetallic Ru complexes exhibit absorption bands attributable to (1)MLCT (Ru --> tpy) transitions. For the heteroleptic complexes, the transitions involving the unsubstituted tpy ligand are at a lower energy than the tpy moiety of the TPBr ligand. The absorption bands observed in the electronic spectra for TPBr and [PdCl(TP)] have been assigned with the aid of TD-DFT calculations. All complexes display weak emission both at room temperature and in a butyronitrile glass at 77 K. The considerable red shift of the emission maxima relative to the signal of the reference compound [Ru(tpy)2]2+ indicates stabilization of the luminescent 3MLCT state. For the mono- and heterometallic complexes, electrochemical and spectroscopic studies (electronic absorption and emission spectra and luminescence lifetimes recorded at room temperature and 77 K in nitrile solvents), together with the information gained from IR spectroelectrochemical studies of the dimetallic complex [Ru(TPPdSCN)(tpy)](PF6)2, are indicative of charge redistribution through the bridging ligand TPBr. The results are in line with a weak coupling between the {Ru(tpy)2} chromophoric unit and the (non)metalated NCN-pincer moiety.     

Infrared multiphoton ionization of superhot C60: experiment and model calculations

We address, both experimentally and theoretically, the issue of infrared (IR) resonance enhanced multiphoton ionization (IR-REMPI) and thermally induced redshifts of IR absorption lines in a very large and highly vibrationally excited molecular system. Isolated superhot C60 molecules with well defined and variable average vibrational energy in the range of 9-19 eV, effusing out of a constant flux thermal source, are excited and ionized after the absorption of multiple (500-800) infrared photons in the 450-1800 cm(-1) spectral energy range. Recording the mass-selected ion signal as a function of IR wavelength gives well resolved IR-REMPI spectra, with zero off-resonance background signal. An enhancement of the ion signal of about a factor of 10 is observed when the temperature is increased from 1200 to 1800 K under otherwise identical conditions. A pronounced temperature dependent redshift of some of the IR absorption lines is observed. The observations are found to be in good agreement with a model which is based on the sequential absorption of single photons, always followed by instantaneous vibrational energy redistribution. The mass spectra (C60(+) fragmentation pattern) are found to be strongly excitation wavelength dependent. Extensive fragmentation down to C32(+) is observed following the absorption of 1350-1400 cm(-1) as well as 1500-1530 cm(-1) photons while negligible fragmentation is observed when exciting around 520 cm(-1).