Further Evidence for ‘Extended’ Cumulene Complexes: Derivatives from Reactions with Halide Anions and Water

Reactions of [Ru{C=C(H)-1,4-C₆H₄C≡CH}(PPh₃)₂Cp]BF₄ ([ 1 a ]BF₄) with hydrohalic acids, HX, results in the formation of [Ru{C≡C-1,4-C₆H₄-C(X)=CH₂}(PPh₃)₂Cp] [X=Cl ( 2 a-Cl ), Br ( 2 a-Br )], arising from facile Markovnikov addition of halide anions to the putative quinoidal cumulene cation [Ru(=C=C=C₆H₄=C=CH₂)(PPh₃)₂Cp]⁺. Similarly, [M{C=C(H)-1,4-C₆H₄-C≡CH}(LL)Cp ]BF₄ [M(LL)Cp’=Ru(PPh₃)₂Cp ([ 1 a ]BF₄); Ru(dppe)Cp* ([ 1 b ]BF₄); Fe(dppe)Cp ([ 1 c ]BF₄); Fe(dppe)Cp* ([ 1 d ]BF₄)] react with H⁺/H₂O to give the acyl-functionalised phenylacetylide complexes [M{C≡C-1,4-C₆H₄-C(=O)CH₃}(LL)Cp’] ( 3 a – d ) after workup. The Markovnikov addition of the nucleophile to the remote alkyne in the cations [ 1 a–d ]⁺ is difficult to rationalise from the vinylidene form of the precursor and is much more satisfactorily explained from initial isomerisation to the quinoidal cumulene complexes [M(=C=C=C₆H₄=C=CH₂)(LL)Cp’]⁺ prior to attack at the more exposed, remote quaternary carbon. Thus, whilst representative acetylide complexes [Ru(C≡C-1,4-C₆H₄-C≡CH)(PPh₃)₂Cp] ( 4 a ) and [Ru(C≡C-1,4-C₆H₄-C≡CH)(dppe)Cp*] ( 4 b ) reacted with the relatively small electrophiles [CN]⁺ and [C₇H₇]⁺ at the β-carbon to give the expected vinylidene complexes, the bulky trityl ([CPh₃]⁺) electrophile reacted with [M(C≡C-1,4-C₆H₄-C≡CH)(LL)Cp’] [M(LL)Cp’=Ru(PPh₃)₂Cp ( 4 a ); Ru(dppe)Cp* ( 4 b ); Fe(dppe)Cp ( 4 c ); Fe(dppe)Cp* ( 4 d )] at the more exposed remote end of the carbon-rich ligand to give the putative quinoidal cumulene complexes [M{C=C=C₆H₄=C=C(H)CPh₃}(LL)Cp’]⁺, which were isolated as the water adducts [M{C≡C-1,4-C₆H₄-C(=O)CH₂CPh₃}(LL)Cp’] ( 6 a–d ). Evincing the scope of the formation of such extended cumulenes from ethynyl-substituted arylvinylene precursors, the rather reactive half-sandwich (5-ethynyl-2-thienyl)vinylidene complexes [M{C=C(H)-2,5-^cC₄H₂S-C≡CH}(LL)Cp’]BF₄ ([ 7 a – d ]BF₄ add water readily to give [M{C≡C-2,5-^cC₄H₂S-C(=O)CH₃}(LL)Cp’] ( 8 a – d )].     

Using Time‐Resolved Electrochemical Patterning to Gain Fundamental Insight into Aryl‐Radical Surface Modification

Scanning electrochemical microscopy is used to carry out local free‐radical grafting at a gold surface through mild oxidation of an aryl hydrazine. The process can be deliberately controlled by creation of a local pH gradient at the tip. Comparison of the experimental results with simulations shows that the radial expansion of the pH profile in which successful grafting can be accomplished increases with increasing generation time of OH^? and with decreasing initial concentration of the grafting precursor. Furthermore, the radial expansion is faster than the nucleation of the grafting process.     

State conditions transferability of vapor–liquid equilibria via fluctuation solution theory with correlation function integrals from molecular dynamics simulation

The ‘State Conditions Transferability’ category of IFPSC 2006 tests prediction of binary vapor–liquid isotherms for mixtures of ethanol and the refrigerant HFF-227ea (1,1,1,2,3,3,3-heptafluoropropane). We predict these isotherms using fluctuation solution theory (FST). The method is based on isobaric–isothermal molecular dynamics (NPT-MD) simulations, using force field parameters published in the literature and fitted CHARMM force field parameters. Systems studied previously [S. Christensen, G.H. Peters, F.Y. Hansen, J.P. O’Connell, J. Abildskov, Molecular Simulation 33 (2007) 449–457] comprise the nearly ideal benzene/methyl acetate system, and the less ideal benzene/ethanol system at ambient temperatures. Both are at low pressures and remote from the pure component critical points. For the IFPSC system, we have used the same method even though predictions are for conditions remote from those of the provided data, the pressures are elevated, and the temperatures are near the critical temperature of one of the components. We first describe the computational method and thermodynamic modeling for the entry submitted, which assumed the vapor was an ideal gas and no Poynting correction was included. Then we discuss the effects of using common modeling methods to estimate the effects of elevated pressures.     

Dipyrrinato-Iridium(III) Complexes for Application in Photodynamic Therapy and Antimicrobial Photodynamic Inactivation

The generation of bio-targetable photosensitizers is of utmost importance to the emerging field of photodynamic therapy and antimicrobial (photo-)therapy. A synthetic strategy is presented in which chelating dipyrrin moieties are used to enhance the known photoactivity of iridium(III) metal complexes. Formed complexes can thus be functionalized in a facile manner with a range of targeting groups at their chemically active reaction sites. Dipyrrins with N- and O-substituents afforded (dipy)iridium(III) complexes via complexation with the respective Cp*-iridium(III) and ppy-iridium(III) precursors (dipy=dipyrrinato, Cp*=pentamethyl-η⁵-cyclopentadienyl, ppy=2-phenylpyridyl). Similarly, electron-deficient [Ir^III(dipy)(ppy)₂] complexes could be used for post-functionalization, forming alkenyl, alkynyl and glyco-appended iridium(III) complexes. The phototoxic activity of these complexes has been assessed in cellular and bacterial assays with and without light; the [Ir^III(Cl)(Cp*)(dipy)] complexes and the glyco-substituted iridium(III) complexes showing particular promise as photomedicine candidates. Representative crystal structures of the complexes are also presented.     

Purity Determination of Phosphorus Compounds by Internat- Standard31 P Nmr Spectroscopy. an Experimental Study and Validation

Abstract

Due to the proportionality between the area of the NMR signal and the number of nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.nuclei, internal standard³¹P NMR spectroscopy is in principle a rapid and simple method for determination of the purity of phosphorus compounds.     

Gas–gas experimental interfacial tension measurement

A thermodynamically stable interface can only exist between two immiscible fluids, nonetheless in this work an “immiscible interface” between two gases (CO₂–methane) has been observed and is documented within this paper. This work is the first ever attempt to measure the interfacial tension (IFT) in a gas–gas system, the interfacial tension of supercritical carbon dioxide (SCO₂–methane) was measured at temperatures of 368.15 and 433.15 K and pressures between 6.9 and 41.37 MPa, using a modified pendant drop method. This study was undertaken to investigate the effects of CO₂ injection into a gas reservoir or enhanced gas recovery.     

Phase behavior, topology, and growth of neutral catanionic reverse micelles

The ternary catanionic system octylammoniumoctanoate/octane/water is studied by combined SANS, light scattering, conductivity, and phase diagram approach in the water-poor microemulsion region. The sphere-to-cylinder growth and branching depends on the concentration, the water-to-surfactant ratio, and the temperature. The unidimensional growth leads to a network of interconnected wormlike micelles. Like most studied linear nonionic surfactants, in this true catanionic system at equimolarity of anionic and cationic surfactant, the curvature toward water increases with temperature, making connections between cylinders less frequent.