Projects per year
Raman and vibrational Raman optical activity (VROA) spectra of helical conformers of polypropylene chains are simulated using ab initio methods to unravel the relationships between the vibrational signatures and the primary and secondary structures of the chains. For a polypropylene chain containing three units, conformational effects are shown to lead to more acute signatures for VROA than for Raman spectra. In addition to regular polypropylene chains, which can display right and left helicities with the same probability, chirality and therefore helicity are enforced by substituting one chain end with a phenyl group. The simulations predict that the threefold helical structures, which correspond to (TG) conformations of the backbone, have a specific VROA backward signature in the form of an intense couplet around 1100 cm . This couplet is associated with collective wagging and twisting motions, while most of its intensity comes from the anisotropic invariants combining normal coordinate derivatives of the electric dipole-electric dipole polarizability and of the electric dipole-magnetic dipole polarizability. A similar signature has already been found in model helical polyethylene chains, whereas it is very weak in forward VROA.
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Liégeois, V., 2006
Supervisor: Champagne, B. (Supervisor)
Student thesis: DEA types › DEA in Chemistry
Elaboration of quantum chemistry methods for predicting and interpreting vibrational Raman optical activity: applications to helical structuresAuthor: Liégeois, V., 19 Jun 2008
Student thesis: Doc types › Doctor of Sciences