Intermolecular interactions in AST zeolites through 14N NMR and DFT calculations. Issue 3 (6th February 2017)

• Record Type: Journal Article
• Authors: Dib, Eddy; Freire, Mélanie; Pralong, Valérie; Mineva, Tzonka; Alonso, Bruno
• Is Part Of: Acta crystallographica. Volume 73:Issue 3(2017)
• Page Start: 202
• Page End: 207
• Publication Date: 2017-02-06
• Subjects: solid‐state NMR -- DFT calculations -- zeolites -- crystal structure -- computational chemistry -- hydrogen bonding; Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229616017022
• Languages: English
• ISSNs: 2053-2296

Abstract

Abstract : The reinvestigation of silica AST zeolite by 14 N NMR and DFT calculations allows the highlighting of intermolecular interactions involving the tetramethylammonium cations and fluoride anions (hydrogen and tetrel bonds) that strengthen the stability of the whole structure. 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 using 14 N NMR quadrupolar parameters and DFT calculations. The value of the experimental 14 N 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 14 N NMR parameters demonstrate the presence of weak C—H…O hydrogen bonds between the TMA in the [4 6 6 12 ] cages and the silica skeleton. These intermolecular interactions can be related to the presence of Si…F tetrel bonds within the [4 6 ] cages. These new results provide additional information with regard to the formation mechanisms and structure of the octadecasil zeolites.