title: Intermolecular interactions in AST zeolites through14N NMR and DFT calculations.
abstract: The structure of the silica AST zeolites (octadecasil) synthesized in fluoride medium using tetramethylammonium (TMA) as the organic structure-directing agent has been reinvestigated using14N NMR quadrupolar parameters and DFT calculations. The value of the experimental14N quadrupolar coupling constant (CQ= 27 kHz) is larger than expected for a TMA cation possessing a high degree of motion. The analysis of a DFT-optimized octadecasil cluster along with the comparison between measured and calculated14N NMR parameters demonstrate the presence of weak C-H...O hydrogen bonds between the TMA in the [46612] cages and the silica skeleton. These intermolecular interactions can be related to the presence of Si...F tetrel bonds within the [46] cages. These new results provide additional information with regard to the formation mechanisms and structure of the octadecasil zeolites.
authors.affiliation: ICGM-MACS, Institut Charles Gerhardt de Montpellier, UMR5253 CNRS-ENSCM-UM, 8 rue de l'école normale, Montpellier Cedex 5, 34296, France.
authors.forename: Eddy
authors.initials: E
authors.lastname: Dib
authors.affiliation: Laboratoire de Cristallographie et Sciences des Matériaux CRISMAT, ENSICAEN, Normandie Université, CNRS, 6 Bd Maréchal Juin, Caen 14050, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Freire
authors.affiliation: Laboratoire de Cristallographie et Sciences des Matériaux CRISMAT, ENSICAEN, Normandie Université, CNRS, 6 Bd Maréchal Juin, Caen 14050, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Pralong
authors.affiliation: ICGM-MACS, Institut Charles Gerhardt de Montpellier, UMR5253 CNRS-ENSCM-UM, 8 rue de l'école normale, Montpellier Cedex 5, 34296, France.
authors.forename: Tzonka
authors.initials: T
authors.lastname: Mineva
authors.affiliation: ICGM-MACS, Institut Charles Gerhardt de Montpellier, UMR5253 CNRS-ENSCM-UM, 8 rue de l'école normale, Montpellier Cedex 5, 34296, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Alonso
keywords: DFT calculations; computational chemistry; crystal structure; hydrogen bonding; solid-state NMR; zeolites