Intermolecular interactions in AST zeolites through 14N NMR and DFT calculations

Dib Eddy (1) , Freire Mélanie (2) , Valérie Pralong (2) , Tzonka Mineva (1) , Bruno Alonso (1)

1 ICGM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier
2 CRISMAT - Laboratoire de cristallographie et sciences des matériaux

The structure of the silica AST zeolites (octa­deca­sil) synthesized in fluoride medium using tetra­methyl­ammonium (TMA) as the organic structure-directing agent has been reinvestigated using 14N NMR quadrupolar parameters and DFT calculations. The value of the experimental 14N 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 calculated 14N 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.

Mots clés: Solid-state NMR; DFT calculations; Zeolites; Crystal structure; Computational chemistry; Hydrogen bonding

Domaines: Chimie théorique et/ou physique; Cristallographie; Chimie inorganique

Dib Eddy, Freire Mélanie, Valérie Pralong, Tzonka Mineva, Bruno Alonso. Intermolecular interactions in AST zeolites through 14N NMR and DFT calculations . Acta Crystallographica Section C : Crystal Structure Communications [1968-2013], 2017, 73, pp.202. ⟨10.1107/S2053229616017022⟩. ⟨hal-01534161⟩