Examinando por Autor "Pinacho, Pablo"
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Ítem Structure Determination, Conformational Flexibility, Internal Dynamics, and Chiral Analysis of Pulegone and Its Complex with Water(Wiley, 2018) Krin, Anna; Pérez-Cuadrado, Cristóbal; Pinacho, Pablo; Quesada-Moreno, María Mar; López-González, Juan Jesús; Avilés-Moreno, Juan Ramón; Blanco-Rodríguez, Susana; López-Alonso, Juan Carlos; Schnell, MelanieIn the current work we present a detailed analysis of the chiral molecule pulegone, which is a constituent of essential oils, using broadband rotational spectroscopy. Two conformers are observed under the cold conditions of a molecular jet. We report an accurate experimentally determined structure for the lowest energy conformer. For both conformers, a characteristic splitting pattern is observed in the spectrum, resulting from the internal rotation of the two non-equivalent methyl groups situated in the isopropylidene side chain. The determined energy barriers are 1.961911(46) kJ/mol and 6.3617(12) kJ/mol for one conformer, and 1.96094(74) kJ/mol and 6.705(44) kJ/mol for the other one. Moreover, a cluster of the lowest energy conformer with one water molecule is reported. The water molecule locks one of the methyl groups via a hydrogen bond and some secondary interactions, so that we only observe internal rotation splittings from the other methyl group with an internal rotation barrier of 2.01013(38) kJ/mol. Additionally, the chirality-sensitive microwave three-wave mixing technique is applied for the differentiation between the enantiomers, which can become of further use for the analysis of essential oils.Ítem Unlocking the Water Trimer Loop: Isotopic Study of Benzophenone-(H2O)1–3 Clusters with Rotational Spectroscopy(Wiley, 2021) Li, Weixing; Quesada-Moreno, María Mar; Pinacho, Pablo; Schnell, MelanieExamined here are the structures of complexes of benzophenone microsolvated with up to three water molecules by using broadband rotational spectroscopy and the cold conditions of a molecular jet. The analysis shows that the water molecules dock sideways on benzophenone for the water monomer and dimer moieties, and they move above one of the aromatic rings when the water cluster grows to the trimer. The rotational spectra shows that the water trimer moiety in the complex adopts an open-loop arrangement. Ab initio calculations face a dilemma of identifying the global minimum between the open loop and the closed loop, which is only solved when zero-point vibrational energy correction is applied. An OH⋅⋅⋅π bond and a Bürgi-Dunitz interaction between benzophenone and the water trimer are present in the cluster. This work shows the subtle balance between water–water and water–solute interactions when the solute molecule offers several different anchor sites for water molecules.