The Experts below are selected from a list of 732 Experts worldwide ranked by ideXlab platform

Babak Borhan - One of the best experts on this subject based on the ideXlab platform.

  • fluorinated porphyrin tweezer a powerful reporter of absolute configuration for erythro and threo diols amino alcohols and diamines
    Journal of the American Chemical Society, 2008
    Co-Authors: Marina Tanasova, Chrysoula Vasileiou, Babak Borhan
    Abstract:

    A general and sensitive nonempirical protocol to determine the absolute configurations of erythro and threo diols, amino alcohols, and diamines is reported. Binding of diols to the porphyrin tweezer system is greatly enhanced by increasing the Lewis acidity of the metalloporphyrin. Supramolecular complexes formed between the porphyrin tweezer host and chiral substrates exhibited exciton-coupled bisignate CD spectra with predictable signs based on the substituents on the chiral center. The working model suggests that the observed helicity of the porphyrin tweezer is dictated via steric differentiation experienced by the porphyrin ring bound to each chiral center. A variety of erythro and threo substrates were investigated to verify this Chiroptical Method. Their absolute configurations were unequivocally determined, and thus a general mnemonic is provided for the assignment of chirality.

Vincent Rodriguez - One of the best experts on this subject based on the ideXlab platform.

  • hyper rayleigh scattering as a new Chiroptical Method uncovering the nonlinear optical activity of aromatic oligoamide foldamers
    Journal of the American Chemical Society, 2020
    Co-Authors: Dominique Verreault, Kevin Moreno, Eric Merlet, Frederic Adamietz, Brice Kauffmann, Yann Ferrand, Celine Olivier, Vincent Rodriguez
    Abstract:

    Molecular helices based on self-organized aromatic oligoamide foldamers have been designed and prepared in their two enantiomeric forms in order to probe their second-order nonlinear Chiroptical properties in solution. The quinoline oligoamides were rationally functionalized by electron-donating and electron-withdrawing groups to afford a gradual increase of the electronic polarization of the helical architectures. Their hyper-Rayleigh scattering (HRS) responses in solution were accordingly assessed, using either linearly polarized or circularly polarized incident light. Both Methods allowed us to observe nonlinear optical activity that was quantified, for the first time for molecular systems, through circular differential scattering intensity ratios. The hyper-Rayleigh optical activity study reveals important charge-transfer differences within the aromatic oligomers, depending on the helix handedness and on the extent of electronic polarization induced by the appended substituents. The origin of the enantiomeric difference is discussed considering both achiral and chiral contributions. Overall, using aromatic oligoamide foldamers as a chiral model, we demonstrate the capabilities of HRS as a complementary Chiroptical Method, ideally suited for the analysis of various chiral molecular and supramolecular systems in solution. The reliability and chiral discrimination sensitivity of the Method can be further improved through dynamic measurements using standard polarization modulation and heterodyning techniques.

Marina Tanasova - One of the best experts on this subject based on the ideXlab platform.

  • fluorinated porphyrin tweezer a powerful reporter of absolute configuration for erythro and threo diols amino alcohols and diamines
    Journal of the American Chemical Society, 2008
    Co-Authors: Marina Tanasova, Chrysoula Vasileiou, Babak Borhan
    Abstract:

    A general and sensitive nonempirical protocol to determine the absolute configurations of erythro and threo diols, amino alcohols, and diamines is reported. Binding of diols to the porphyrin tweezer system is greatly enhanced by increasing the Lewis acidity of the metalloporphyrin. Supramolecular complexes formed between the porphyrin tweezer host and chiral substrates exhibited exciton-coupled bisignate CD spectra with predictable signs based on the substituents on the chiral center. The working model suggests that the observed helicity of the porphyrin tweezer is dictated via steric differentiation experienced by the porphyrin ring bound to each chiral center. A variety of erythro and threo substrates were investigated to verify this Chiroptical Method. Their absolute configurations were unequivocally determined, and thus a general mnemonic is provided for the assignment of chirality.

Dominique Verreault - One of the best experts on this subject based on the ideXlab platform.

  • hyper rayleigh scattering as a new Chiroptical Method uncovering the nonlinear optical activity of aromatic oligoamide foldamers
    Journal of the American Chemical Society, 2020
    Co-Authors: Dominique Verreault, Kevin Moreno, Eric Merlet, Frederic Adamietz, Brice Kauffmann, Yann Ferrand, Celine Olivier, Vincent Rodriguez
    Abstract:

    Molecular helices based on self-organized aromatic oligoamide foldamers have been designed and prepared in their two enantiomeric forms in order to probe their second-order nonlinear Chiroptical properties in solution. The quinoline oligoamides were rationally functionalized by electron-donating and electron-withdrawing groups to afford a gradual increase of the electronic polarization of the helical architectures. Their hyper-Rayleigh scattering (HRS) responses in solution were accordingly assessed, using either linearly polarized or circularly polarized incident light. Both Methods allowed us to observe nonlinear optical activity that was quantified, for the first time for molecular systems, through circular differential scattering intensity ratios. The hyper-Rayleigh optical activity study reveals important charge-transfer differences within the aromatic oligomers, depending on the helix handedness and on the extent of electronic polarization induced by the appended substituents. The origin of the enantiomeric difference is discussed considering both achiral and chiral contributions. Overall, using aromatic oligoamide foldamers as a chiral model, we demonstrate the capabilities of HRS as a complementary Chiroptical Method, ideally suited for the analysis of various chiral molecular and supramolecular systems in solution. The reliability and chiral discrimination sensitivity of the Method can be further improved through dynamic measurements using standard polarization modulation and heterodyning techniques.

Chrysoula Vasileiou - One of the best experts on this subject based on the ideXlab platform.

  • fluorinated porphyrin tweezer a powerful reporter of absolute configuration for erythro and threo diols amino alcohols and diamines
    Journal of the American Chemical Society, 2008
    Co-Authors: Marina Tanasova, Chrysoula Vasileiou, Babak Borhan
    Abstract:

    A general and sensitive nonempirical protocol to determine the absolute configurations of erythro and threo diols, amino alcohols, and diamines is reported. Binding of diols to the porphyrin tweezer system is greatly enhanced by increasing the Lewis acidity of the metalloporphyrin. Supramolecular complexes formed between the porphyrin tweezer host and chiral substrates exhibited exciton-coupled bisignate CD spectra with predictable signs based on the substituents on the chiral center. The working model suggests that the observed helicity of the porphyrin tweezer is dictated via steric differentiation experienced by the porphyrin ring bound to each chiral center. A variety of erythro and threo substrates were investigated to verify this Chiroptical Method. Their absolute configurations were unequivocally determined, and thus a general mnemonic is provided for the assignment of chirality.