Vincent Liégeois

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We present an analytical time-dependent Hartree-Fock algorithm for the calculation of the derivatives of the electric dipole-magnetic dipole polarizability with respect to atomic Cartesian coordinates. Combined with analogous procedures to determine the derivatives of the electric dipole-electric dipole and electric dipole-electric quadrupole(More)
We present an extensive investigation of the dependence of the scattering intensity difference of right and left circularly polarized light observed in vibrational Raman optical activity (VROA) on the choice of basis set and exchange-correlation functional. These dependencies are investigated for five molecules for which accurate experimental data are(More)
Analytical procedures based on the time-dependent Hartree-Fock (TDHF) scheme are elaborated to evaluate the frequency-dependent electric dipole-electric quadrupole polarizability and its derivatives with respect to atomic Cartesian coordinates. On one hand, the mixed second-order TDHF equations are solved iteratively to obtain the second-order derivatives(More)
In a previous study [Lamparska, E.; Liégeois, V.; Quinet, O.; Champagne, B. ChemPhysChem 2006, 7, 2366-2376], signatures associated to the helical structure of a small oligomer of a polypropylene chain were highlighted in the vibrational Raman optical activity (VROA) spectra. Nevertheless, it was difficult to pursue the analysis of longer chains. Indeed,(More)
Using density functional theory, we calculate the IR and Raman signatures of the thiophenol (TP) molecule adsorbed on gold clusters by mimicking the different types of adsorption sites, and we analyze these signatures by using advanced tools implemented into the pyvib2 program. First, we follow the evolution of the vibrational normal modes from the isolated(More)
Using theoretical simulations based on Hartree-Fock and density-functional theory calculations, the simulated vibrational Raman optical activity spectra of helical conformers of heptasilane are shown to present signatures sensitive to the helicity. These signatures are associated with collective wagging, twisting, and rocking motions. These simulated(More)
Restricted Hartree-Fock computations are reported for a methyl isocyanide polymer (repeating unit -C═N-CH3), whose most stable conformation is expected to be a helical chain. The computations used a standard contracted Gaussian orbital set at the computational levels STO-3G, 3-21G, 6-31G, and 6-31G**, and studies were made for two line-group configurations(More)
The Raman polarized and vibrational Raman optical activity (VROA) backward spectra are simulated for a series of 2,2'-substituted 1,1'-binaphthyl compounds presenting a variety of torsion angles between the two naphthalene rings. The substitution prevents free rotation along this torsion angle and the chirality of these compounds is thus called(More)
The synthesis and the separation of the four stereoisomers of 2,4,6,8,10-pentamethylundecane (PMU) are described together with their characterization by Raman spectroscopy. In parallel, theoretical calculations of the Raman and vibrational Raman optical activity (VROA) spectra are reported and analyzed in relation with the recorded spectra. A very good(More)
Detailed information on the architecture of polyisocyanopeptides based on vibrational circular dichroism (VCD) spectroscopy in combination with DFT calculations is presented. It is demonstrated that the screw sense of the helical polyisocyanides can be determined directly from the C=N-stretch vibrational region of the VCD spectrum. Analysis of the VCD(More)