The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform

Walter Purcell - One of the best experts on this subject based on the ideXlab platform.

Johann G. Leipoldt - One of the best experts on this subject based on the ideXlab platform.

  • The crystal structure of (AsPh4)2[Re(NO)(H2O)(CN)4]·5H2O
    Polyhedron, 1995
    Co-Authors: John M. A. Smith, Walter Purcell, Gert J. Lamprecht, Johann G. Leipoldt
    Abstract:

    Abstract The crystal structure of (AsPh4)2[Re(NO)(H2O)(CN)4]·5H2O has been determined from three-dimensional X-ray diffraction data. The [Re(NO)(H2O)(CN)4]2− ion has a distorted octahedral geometry with the following bond distances: ReNO = 1.732(7), ReOH2 = 2.165(5) and Re  CN av = 2.09 A . The NO group bond is at 178.4(7)° to the Rhenium Atom and N  O = 1.181(8) A . The Rhenium Atom is displaced by 0.17 A out of the plane formed by the four carbon Atoms of the cyano ligands towards the nitrosyl ligand.

  • Crystal structure of tetraphenylarsonium aquatetracyanonitridorhenate(V), (AsPh_4)_2 [ReN(H_2O)(CN)_4]·5H_2O
    Transition Metal Chemistry, 1992
    Co-Authors: Walter Purcell, Izak M. Potgieter, Llewellyn J. Damoense, Johann G. Leipoldt
    Abstract:

    The crystal structure of (AsPh_4)_2[ReN(H_2O)(CN)_4]·5H_2O has been determined from three-dimensional X-ray diffraction data. The yellow crystals are monoclinic, space group P2_1/n with cell dimensions a =15.482(1), b =19.950(2), c =16.999(1)Å and β=101.69(6)^o, Z =4, D _expt=1.48(1)g cm^−3 and D _calc=1.52g cm^−3. The anisotropic refinement of 7858 observed reflections converged to R =0.055. The [ReN(H_2O)(CN)_4]^2− ion has a distorted octahedral geometry. Bond distances: Re≡N=1.639(8), Re−OH_2=2.496(7) and Re−C_(av)=2.11(1) Å. The Rhenium Atom is displaced by 0.35 Å out of the plane formed by the four carbon Atoms of the cyano ligands towards the terminal nitrido ligand.

  • The crystal structure of tetraethylammonium aquatetracyanooxorhenate(V)
    Transition Metal Chemistry, 1990
    Co-Authors: Walter Purcell, Andreas Roodt, Stephen S. Basson, Johann G. Leipoldt
    Abstract:

    The crystal structure of the tetraethylammonium salt of [ReO(H_2O)(CN)_4]^− has been determined from threedimensional x-ray diffraction data. The light blue crystals are monoclinic, space group P2_1/m with a =8.760(1), b =9.518(5), c =11.718(1) Å, β=102.63(1)^o with two molecules per unit cell. The final R value using 2009 observed reflections and anisotropic thermal parameters for all the non-hydrogen Atoms was 0.038. The [ReO(H_2O)(CN)_4]^− ion has a distorted octahedral geometry with the Rhenium Atom displaced by 0.30 Å out of the plane formed by the four carbon Atoms of the cyano ligands towards the oxo ligand. Bond distances: Re=O=1.667(8), Re−OH_2=2.142(7) and Re−C (average)=2.11(1) Å.

Stephen S. Basson - One of the best experts on this subject based on the ideXlab platform.

Jeanne Crassous - One of the best experts on this subject based on the ideXlab platform.

  • a chiral Rhenium complex with predicted high parity violation effects synthesis stereochemical characterization by vcd spectroscopy and quantum chemical calculations
    Physical Chemistry Chemical Physics, 2013
    Co-Authors: Nidal Saleh, Samia Zrig, Radovan Bast, Trond Saue, Benoit Darquie, Thierry Roisnel, Jeanne Crassous
    Abstract:

    With their rich electronic, vibrational, rotational and hyperfine structure, molecular systems have the potential to play a decisive role in precision tests of fundamental physics. For example, electroweak nuclear interactions should cause small energy differences between the two enantiomers of chiral molecules, a signature of parity symmetry breaking. Enantioenriched oxoRhenium(VII) complexes S-(−)- and R-(+)-3 bearing a chiral 2-methyl-1-thio-propanol ligand have been prepared as potential candidates for probing molecular parity violation effects via high resolution laser spectroscopy of the ReO stretching. Although the Rhenium Atom is not a stereogenic centre in itself, experimental vibrational circular dichroism (VCD) spectra revealed a surrounding chiral environment, evidenced by the ReO bond stretching mode signal. The calculated VCD spectrum of the R enantiomer confirmed the position of the sulfur Atom cis to the methyl, as observed in the solid-state X-ray crystallographic structure, and showed the presence of two conformers of comparable stability. Relativistic quantum chemistry calculations indicate that the vibrational shift between enantiomers due to parity violation is above the target sensitivity of an ultra-high resolution infrared spectroscopy experiment under active preparation.

  • Chiral oxoRhenium(V) complexes as candidates for the experimental observation of molecular parity violation: a structural, synthetic and theoretical study.
    Physical Chemistry Chemical Physics, 2010
    Co-Authors: Frederic De Montigny, Radovan Bast, Trond Saue, Nicolas Vanthuyne, Christian Roussel, Andre Severo Pereira Gomes, Guillaume Pilet, Laure Guy, Peter Schwerdtfeger, Jeanne Crassous
    Abstract:

    We report the synthesis and resolution of a series of new chiral "3 + 1" oxoRhenium(V) complexes, designed for high-resolution laser spectroscopy experiments probing molecular parity-violation (PV) effects in the Re=O stretching mode frequency. These complexes display a particularly simple chemical structure, with the Rhenium Atom as the stereogenic center, and show large PV energy differences according to our calculations. They were obtained in the racemic and enantioenriched forms, in the latter case by using either semi-preparative chiral HPLC resolution or enantioselective synthesis. The vibrational transition frequency differences between the enantiomeric pairs due to PV have been calculated with two- and four-component relativistic Hamiltonians using Hartree-Fock (HF) and density functional theory (DFT). For three complexes, including one synthesized in enantioenriched form, our HF calculations predict frequency differences above the present resolution limit of 1 Hz. These results confirm the order of magnitude for the calculated HF PV vibrational frequency differences reported earlier for this class of compounds [P. Schwerdtfeger and R. Bast, J. Am. Chem. Soc., 2004, 126, 1652]. However, at the DFT level the PV vibrational frequency differences are in some cases reduced by an order of magnitude, but are still within the sensitivity of 0.01 Hz, which is the anticipated sensitivity in a new proposed experiment. We therefore believe that the present study represents an important step towards the experimental observation of PV in molecular systems, and emphasizes the extreme sensitivity of the PV vibrational frequency difference to the chemical environment around the Rhenium center.

Niyazi Serdar Sariciftci - One of the best experts on this subject based on the ideXlab platform.

  • Using the Alkynyl-Substituted Rhenium(I) Complex (4,4′-Bisphenyl-Ethynyl-2,2′-Bipyridyl)Re(CO)_3Cl as Catalyst for CO_2 Reduction—Synthesis, Characterization, and Application
    Electrocatalysis, 2015
    Co-Authors: Engelbert Portenkirchner, Kerstin Oppelt, Daniel A M Egbe, Helmut Neugebauer, Gunther Knor, Dogukan Apaydin, Markus Himmelsbach, Stefanie Schlager, Tsukasa Yoshida, Niyazi Serdar Sariciftci
    Abstract:

    The synthesis, structure, photophysics, and spectroscopic characterization of an organometallic Rhenium multichromophore compound carrying a central 2,2′-bipyridyl acceptor moiety with additional phenylethynyl substituents conjugated at the 4,4′-positions of the acceptor ligands and its effect on the electron density of the central Rhenium Atom as metal center for CO_2 reduction is reported. The results were compared to fac -(2,2′-bipyridyl)Re(CO)_3Cl and fac -(5,5′-bisphenylethynyl-2,2′-bipyridyl)Re(CO)_3Cl. Cyclovoltammetric studies and rotating disk electrochemistry were performed for electrochemical characterization. Ultraviolet and visible (UV-vis) absorption, Fourier transform infrared (FTIR), and luminescence measurements were carried out for a spectroscopic characterization and compared to theoretical calculations at the density functional theory (DFT) level. In addition, the Rhenium complex fac -(4,4′-bisphenyl-ethynyl-2,2′-bipyridyl)-Re(CO)_3Cl was used as a novel catalyst for the electrochemical reduction of CO_2 in homogeneous solution. Results showed an 11-fold increase in the current density under CO_2 saturation and a catalytic second-order rate constant for CO formation of about 560 M^−1 s^−1 on a Pt working electrode. For further characterization of the CO_2 reduction capabilities, bulk controlled potential electrolysis experiments were performed using a CO_2-saturated acetonitrile electrolyte solution. The headspace product gas analysis yields CO as main reduction product with faradaic efficiencies of about 12 % over 5-h electrolysis time. Graphical Abstract

  • using the alkynyl substituted Rhenium i complex 4 4 bisphenyl ethynyl 2 2 bipyridyl re co 3cl as catalyst for co2 reduction synthesis characterization and application
    Electrocatalysis, 2015
    Co-Authors: Engelbert Portenkirchner, Kerstin Oppelt, Daniel A M Egbe, Helmut Neugebauer, Gunther Knor, Dogukan Apaydin, Markus Himmelsbach, Stefanie Schlager, Tsukasa Yoshida, Niyazi Serdar Sariciftci
    Abstract:

    The synthesis, structure, photophysics, and spectroscopic characterization of an organometallic Rhenium multichromophore compound carrying a central 2,2′-bipyridyl acceptor moiety with additional phenylethynyl substituents conjugated at the 4,4′-positions of the acceptor ligands and its effect on the electron density of the central Rhenium Atom as metal center for CO2 reduction is reported. The results were compared to fac-(2,2′-bipyridyl)Re(CO)3Cl and fac-(5,5′-bisphenylethynyl-2,2′-bipyridyl)Re(CO)3Cl. Cyclovoltammetric studies and rotating disk electrochemistry were performed for electrochemical characterization. Ultraviolet and visible (UV-vis) absorption, Fourier transform infrared (FTIR), and luminescence measurements were carried out for a spectroscopic characterization and compared to theoretical calculations at the density functional theory (DFT) level. In addition, the Rhenium complex fac-(4,4′-bisphenyl-ethynyl-2,2′-bipyridyl)-Re(CO)3Cl was used as a novel catalyst for the electrochemical reduction of CO2 in homogeneous solution. Results showed an 11-fold increase in the current density under CO2 saturation and a catalytic second-order rate constant for CO formation of about 560 M−1 s−1 on a Pt working electrode. For further characterization of the CO2 reduction capabilities, bulk controlled potential electrolysis experiments were performed using a CO2-saturated acetonitrile electrolyte solution. The headspace product gas analysis yields CO as main reduction product with faradaic efficiencies of about 12 % over 5-h electrolysis time.