Poly(9,9'-spirobifluorene-manganese porphyrin): a new catalytic material for oxidation of alkenes by iodobenzene diacetate and iodosylbenzene

Anodic oxidation of tetraspirobifluorene-manganese porphyrin lead to the coating of the working electrode by insoluble electroactive poly(9,9'-spirobifluorene-manganese porphyrin) films for which electrochemical behaviour and physicochemical properties are described; these polymeric materials are able to catalyze the heterogeneous epoxidation of styrene with iodobenzene diacetate and iodosylbenzene.     

Mononuclear and dinuclear copper(I) complexes with a particularly bulky phosphine ligand. Unusual synthesis and crystal structure characterizations

Summary The addition of NPm (diphenylaminodiphenylphosphinomethane) to CuI or the addition of KI to (NPm)₂CuNO₃ leads to the same P-bonded Cu^I complex, (NPm)₂CuI, presenting a trigonal geometry around the Cu atom. The reaction of this new complex (or of its chloro analogue) with a Cu^II salt yields dinuclear species of general formula [(NPm)Cu(-X)₂Cu(NPm)] (X = Cl or I). X-ray analysis of these complexes show that they are isostructural and retain the trigonal geometry around the metal atom. The Cu···Cu distances are 2.775(1)Å for X = Cl and 2.642(1) Å for X = I. The Cu-(-X)-Cu angle is more acute for the iodide [61.48(3)°] than for the chloride [74.17(8)°] complex. These values are discussed in terms of Cu···Cu interactions induced by the electron donor ability of X and the bulk of the phosphine L.     

Identification of flavonoids using liquid chromatography with electrospray ionization and ion trap tandem mass spectrometry with an MS/MS library

Searchable MS/MS spectra libraries, constructed using the results of liquid chromatography coupled with electrospray ionization (ESI) tandem mass spectrometry (LC/MS/MS) with data-dependent acquisition on an ion trap mass spectrometer, are presented with regard to the identification and confirmation of a variety of closely related flavonoids in a set of biological samples. Flavonoids were found to exhibit a maximum amount of structurally specific MS/MS spectra at 45% of normalized collision energy on the instrument used, without wideband activation. These MS/MS spectra were then searched automatically against a 297-substance MS/MS library that contains many previously acquired spectra of standard flavonoids. The possible applications of this powerful technique to biological samples are also discussed. Daidzein and genistein were identified through the MS/MS spectra library while searching through LC/MS/MS data for plant and microbial extracts. Moreover, these compounds proved completely distinguishable from other flavonoids of closely related structures in the MS/MS spectra library, using the NIST MS search program. The applicability of the library-searchable spectra at low concentrations was demonstrated by successful identification of daidzein and genistein at 0.05 and 0.5 microg/mL, respectively.     

Surface modification of γ-alumina membranes by silane coupling for CO2 separation

Top layers of γ-Al₂O₃ composite membranes have been modified by the silane coupling technique using phenyltriethoxysilane for improving the separation factor of CO₂ to N₂. The separation efficiency of the modified membranes was strongly dependent upon the hydroxylation tendency of the support materials and the amount of the special functional group (i.e. phenyl radical) which was coupled onto a top layer. The separation factor through the TiO₂ supported γ-Al₂O₃ membrane was found to be fairly enhanced by silane coupling, but in case of the -Al₂O₃ supported membrane was not. The CO₂/N₂ separation factor through the modified γ-Al₂O₃/TiO₂ composite membrane is 1.7 at 90°C and ΔP = 2 × 10⁵ Pa for the binary mixture containing 50 vol% CO₂. The separation factor is proportional to the CO₂ concentration in the gas mixture, and the modified membrane is stable up to 100°C. The main mechanism of the CO₂ transport through the modified γ-Al₂O₃ layer is known to be a surface diffusion.     

Biocatalytic precipitation induced by an affinity reaction on dendrimer-activated surfaces for the electrochemical signaling from immunosensors

We have developed a strategy of signal generation for immunosensors that transduces biospecific affinity recognition reactions into electrochemical signals. The cyclic voltammetric method, tracking the precipitation of insoluble products onto the sensing surface and the subsequent decrement in the electrode area, was chosen for signal registration. Precipitation of insolubilities was induced by the catalytic reaction of enzymes, which were labeled to the biospecifically attached protein or antibody molecules. As a model system for affinity recognition, we have investigated the functionalization of biotin groups to the sensing monolayer and their biospecific interactions with anti-biotin antibody molecules. The immunosensing interface was developed onto the dendrimer-activated self-assembled monolayers (SAMs), as the base template for the functionalization of the antigen moiety and signal generation. The advantages of using dendrimer-activated SAMs in comparison to the plain modified thiolate SAMs for the sensing surface were shown in terms of sensing performances, and the analytical characteristics of the resulting immunosensor were examined. Additionally, the sensing system was applied for biotin/(strept)avidin couples, extending the applicability of the developed strategy.     

Phase coexistence in heterogeneous porous media: a new extension to Gibbs ensemble Monte Carlo simulation method

The effect of confinement on phase behavior of simple fluids is still an area of intensive research. In between experiment and theory, molecular simulation is a powerful tool to study the effect of confinement in realistic porous materials, containing some disorder. Previous simulation works aiming at establishing the phase diagram of a confined Lennard-Jones-type fluid, concentrated on simple pore geometries (slits or cylinders). The development of the Gibbs ensemble Monte Carlo technique by Panagiotopoulos [Mol. Phys. 61, 813 (1987)], greatly favored the study of such simple geometries for two reasons. First, the technique is very efficient to calculate the phase diagram, since each run (at a given temperature) converges directly to an equilibrium between a gaslike and a liquidlike phase. Second, due to volume exchange procedure between the two phases, at least one invariant direction of space is required for applicability of this method, which is the case for slits or cylinders. Generally, the introduction of some disorder in such simple pores breaks the initial invariance in one of the space directions and prevents to work in the Gibbs ensemble. The simulation techniques for such disordered systems are numerous (grand canonical Monte Carlo, molecular dynamics, histogram reweighting, N-P-T+test method, Gibbs-Duhem integration procedure, etc.). However, the Gibbs ensemble technique, which gives directly the coexistence between phases, was never generalized to such systems. In this work, we focus on two weakly disordered pores for which a modified Gibbs ensemble Monte Carlo technique can be applied. One of the pores is geometrically undulated, whereas the second is cylindrical but presents a chemical variation which gives rise to a modulation of the wall potential. In the first case almost no change in the phase diagram is observed, whereas in the second strong modifications are reported.     

Particle interactions in electrophoresis: I. Motion of two spheres along their line of centers

The electrophoretic motion of two charged colloidal spheres with very thin electrical double layers in a constant applied electric field along their line of centers is considered. The particles may differ in radius and in zeta potential at the surface. The electrostatic and hydrodynamic governing equations are solved in the quasi-steady situation using bipolar coordinates and the electrophoretic velocities of particles are calculated for various cases. The interaction effect between particles can be very significant when the distance between particle surfaces gets close to zero. The particle with smaller zeta potential is speeded up by the motion of the other, which is retarded at the same time by the motion of the former one, if the two spheres have unequal zeta potentials of the same electrical sign. For two particles of different signs in zeta potential, motions of both are hindered by each other. The influence of the interaction between particles in general is stronger on the smaller one than on the larger one. For the special case of two electrophoretic spheres with identical zeta potentials, there is no particle interaction for all particle sizes and separations.     

Efficient excitation energy transfer in long meso-meso linked Zn(II) porphyrin arrays bearing a 5,15-bisphenylethynylated Zn(II) porphyrin acceptor

Electronically coupled porphyrin arrays are suitable for artificial light harvesting antenna in light of a large absorption cross-section and fast excitation energy transfer (EET). Along this line, an artificial energy transfer model system has been synthesized, comprising of an energy donating meso-meso linked Zn(II) porphyrin array and an energy accepting 5,15-bisphenylethynylated Zn(II) porphyrin linked via a 1,4-phenylene spacer. This includes an increasing number of porphyrins in the meso-meso linked Zn(II) porphyrin array, 1, 2, 3, 6, 12, and 24 (Z1A, Z2A, Z3A, Z6A, Z12A, and Z24A). The intramolecular singlet-singlet EET processes have been examined by means of the steady-state and time-resolved spectroscopic techniques. The steady-state fluorescence comes only from the acceptor moiety in Z1A-Z12A, indicating nearly the quantitative EET. In Z24A that has a molecular length of ca. 217 A, the fluorescence comes largely from the acceptor moiety but partly from the long donor array, indicating that the intramolecular EET is not quantitative. The transient absorption spectroscopy has provided the EET rates in real time scale: (2.5 ps)(-1) for Z1A, (3.3 ps)(-1) for Z2A, (5.5 ps)(-1) for Z3A, (21 ps)(-1) for Z6A, (63 ps)(-1) for Z12A, and (108 ps)(-1) for Z24A. These results have been well explained by a revised F?rster equation (Sumi formula), which takes into account an exciton extending coherently over several porphyrin pigments in the donor array, whose length is not much shorter than the average donor-acceptor distance. Advantages of such strongly coupled porphyrin arrays in light harvesting and transmission are emphasized in terms of fast EET and a large absorption cross-section for incident light.     

Elucidating interactions of ionic liquids with polymer films using confocal Raman spectroscopy

We report on the molecular interactions between room-temperature ionic liquids (RTILs) and Nafion and PDMS membranes, proving that in contact with these polymers RTILs behave like electrolytes rather than solvents.