title: O-H⋅⋅⋅N and C-H⋅⋅⋅O hydrogen bonds control hydration of pivotal tropane alkaloids: tropinone⋅⋅⋅H(2)O complex.
abstract: The effect of monohydration in equatorial/axial isomerism of the common motif of tropane alkaloids is investigated in a supersonic expansion by using Fourier-transform microwave spectroscopy. The rotational spectrum reveals the equatorial isomer as the dominant species in the tropinone⋅⋅⋅H2 O complex. The monohydrated complex is stabilized primarily by a moderate OH⋅⋅⋅N hydrogen bond. In addition, two CH⋅⋅⋅O weak hydrogen bonds also support this structure, blocking the water molecule and avoiding any molecular dynamics in the complex. The water molecule acts as proton donor and chooses the ternary amine group over the carbonyl group as a proton acceptor. The experimental work is supported by theoretical calculations; the accuracy of the B3LYP, M06-2X, and MP2 methods is also discussed.
authors.affiliation: Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV-EHU), Apartado 644, 48940 Bilbao (Spain) http://grupodeespectroscopia.es/MW/
authors.forename: Patricia
authors.initials: P
authors.lastname: Ecija
authors.forename: Montserrat
authors.initials: M
authors.lastname: Vallejo-López
authors.forename: Luca
authors.initials: L
authors.lastname: Evangelisti
authors.forename: José A
authors.initials: JA
authors.lastname: Fernández
authors.forename: Alberto
authors.initials: A
authors.lastname: Lesarri
authors.forename: Walther
authors.initials: W
authors.lastname: Caminati
authors.forename: Emilio J
authors.initials: EJ
authors.lastname: Cocinero
mesh_terms: D000470:Alkaloids / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D007536:Isomerism; D010100:Oxygen / Q000737:chemistry; D013816:Thermodynamics; D014326:Tropanes / Q000737:chemistry*
chemical_list: D000470:Alkaloids; D014326:Tropanes; C016808:3-tropinone; D002244:Carbon; D006859:Hydrogen; D010100:Oxygen
keywords: alkaloids; dissociation energy; hydrogen bonds; microwave spectroscopy; quadrupole coupling constants