Examinando por Autor "Claramunt, Rosa M."
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Ítem Self-assembly structures of 1H-indazoles in solution and solid phases: A vibrational (IR, FarIR, Raman and VCD) and computational study(Wiley, 2013) Avilés-Moreno, Juan Ramón; Quesada-Moreno, María del Mar; López-González, Juan Jesús; Claramunt, Rosa M.; López-García, Concepción; Alkorta, Ibon; Elguero, José1H-indazoles are good candidates to study phenomena of molecular association and spontaneous resolution of chiral compounds. Thus, because the 1H-indazoles can crystallize forming dimers, trimers or catemers, depending on their structure and the phase where they are, the difficulty of the experimental analysis of the structure of the family of 1H-indazoles is clear. This lead to contemplate several questions: How can we determine the presence of different structures of a determined molecular species if they change according to the phase? Could these different structures be present in the same phase simultaneously? How can it be determined? In order to shed light on these questions, we outline a very complete strategy by using different techniques of vibrational spectroscopy sensitive (VCD) and not sensitive (IR, FarIR and Raman) to the chirality together with quantum chemical calculations.Ítem Supramolecular organization of perfluorinated 1H-indazoles in the solid state using X-ray crystallography, SSNMR and sensitive (VCD) and non sensitive (MIR, FIR and Raman) to chirality vibrational spectroscopies(Royal Society of Chemistry, 2017) Quesada-Moreno, María del Mar; Avilés-Moreno, Juan Ramón; López-González, Juan Jesús; Jacob, Kane; Vendier, Laure; Etienne, Michel; Alkorta, Ibon; Elguero, José; Claramunt, Rosa M.1H-Indazole derivatives exhibit a remarkable property since some of them form chiral supramolecular structures starting from achiral monomers. The present work deals with the study of three perfluorinated 1H-indazoles that resolve spontaneously as conglomerates. These conglomerates can contain either a pure enantiomer (one helix) or a mixture of both enantiomers (both helices) with an enantiomeric excess (e.e.) of one of them. The difficulty of the structural analysis of these types of compounds is thus clear. We outline a complete strategy to determine the structures and configurations (M or P helices) of the enantiomers (helices) forming the conglomerates of these perfluorinated 1H-indazoles based on X-ray crystallography, solid state NMR spectroscopy and different solid state vibrational spectroscopies that are either sensitive (VCD) or not (FarIR, IR and Raman) to chirality, together with quantum chemical calculations (DFT).Ítem Vibrational circular dichroism (VCD) methodology for the measurement of enantiomeric excess in chiral compounds in solid phase and for the complementary use of NMR and VCD techniques in solution: the camphor case(Royal Society of Chemistry, 2018) Quesada-Moreno, María del Mar; Virgili, Albert; Monteagudo, Eva; Claramunt, Rosa M.; Avilés-Moreno, Juan Ramón; López-González, Juan Jesús; Alkorta, Ibon; Elguero, JoséFor the first time, the success of a methodology for the determination of enantiomeric excesses (% ee) in chiral solid samples by vibrational circular dichroism (VCD) spectroscopy is reported. We have used camphor to determine the % ee in a blind sample constituted by a mixture of its two enantiomers as a test of the validity of our approach. IR and VCD spectra of different enantiomeric mixtures of R/S-camphor in nujol mulls were recorded and linear regressions of VCD intensities (ΔAbs.) vs. % ee for selected bands were found. Finally, the VCD intensities of a blind sample were interpolated in these linear regressions, obtaining its % ee with a rms of 2.4. These results in the solid phase were complemented with the determination of % ee in the liquid phase by VCD and NMR techniques, which are proved to be complementary techniques to carry out this kind of analysis. In the same way as in the VCD solid phase, linear regressions of ΔAbs. vs. % ee for selected bands were established, obtaining a rms of 1.1 in the % ee determination of a blind sample. 1H NMR experiments at 600 MHz using the chiral solvating agent, (S,S)-ABTE, allow to determine in CD2Cl2 solution the proportions of enantiomers with great accuracy. 13C CPMAS NMR spectra prove that this technique cannot be used for conglomerates and/or solid solutions.