title: A butterfly motion of formic acid and cyclobutanone in the 1 : 1 hydrogen bonded molecular cluster.
abstract: Upon supersonic expansion, formic acid and cyclobutanone (CBU) form a molecular cluster in which the two constituent molecules, linked by OHO and CHO hydrogen bonds, undergo a rapid interconversion between two equivalent forms. The tunneling motion takes place through the rupture and reformation of the C-HO hydrogen bond between the carbonyl oxygen of HCOOH and one of the two hydrogen atoms of the methylenic group adjacent to the cyclobutanone keto group. From the microwave spectra, tunneling energy splittings (ΔE01) have been determined for the parent (1122.756(3) MHz), DCOOHCBU (1084.538(1) MHz) and HCOODCBU (1180.282(4) MHz) isotopic species. From these splittings, the potential barrier to interconversion has been calculated to be B2= 39.7(5) cm-1. The tunneling pathway is an asymmetric butterfly-like motion between the two moieties of the adduct, with a barrier at a configuration in which the ring plane of cyclobutanone is coplanar with formic acid.
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università, Via Selmi 2, I-40126 Bologna, Italy. walther.caminati@unibo.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Evangelisti
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università, Via Selmi 2, I-40126 Bologna, Italy. walther.caminati@unibo.it.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Spada
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università, Via Selmi 2, I-40126 Bologna, Italy. walther.caminati@unibo.it.
authors.forename: Weixing
authors.initials: W
authors.lastname: Li
authors.affiliation: Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, E-47011 Valladolid, Spain. lesarri@qf.uva.es.
authors.forename: Susana
authors.initials: S
authors.lastname: Blanco
authors.affiliation: Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, E-47011 Valladolid, Spain. lesarri@qf.uva.es.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: López
authors.affiliation: Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, E-47011 Valladolid, Spain. lesarri@qf.uva.es.
authors.forename: Alberto
authors.identifier: http://orcid.org/0000-0002-0646-6341
authors.initials: A
authors.lastname: Lesarri
authors.affiliation: Institut für Physikalische Chemie und Elektrochemie, Lehrgebiet A, Gottfried-Wilhelm-Leibniz-Universität, Callinstrasse 3A, D-30167 Hannover, Germany.
authors.forename: Jens-Uwe
authors.initials: JU
authors.lastname: Grabow
authors.affiliation: Dipartimento di Chimica "G. Ciamician" dell'Università, Via Selmi 2, I-40126 Bologna, Italy. walther.caminati@unibo.it.
authors.forename: Walther
authors.initials: W
authors.lastname: Caminati