Host-Guest Interactions in Zeolites P1, SUZ-4 and ZSM-57 Containing N,N,N,N´,N´,N´-Hexaethylpentane-diammonium Ion as a Guest Molecule

Abstract

The H-1-C-13 CP MAS NMR and Raman spectra of N,N,N,N',N',N'-hexaethylpentanediammonium (Et-6-diquat-5) ions encapsulated within P1, SUZ-4, and ZSM-57 zeolites are presented. The Et-6-diquat-5 molecules occluded are found to adopt distinct molecular conformations in order to fit in the pores of each zeolite host. Computer modeling studies show that encapsulation of Et-6-diquat-5 in the small-pore zeolite P1 is not energetically favorable. However, a remarkable match between the conformation of guest molecule and the geometry of the host structure is observed for the medium-pore zeolites SUZ-4 and ZSM-57, revealing the existence of organic structure-directing effect. The overall results of this study suggest that conformations available to the flexible, linear organic cation like Et-6-diquat-5 may differ considerably according to the type and concentration of alkali cations present in the zeolite synthesis mixture, which is a critical factor affecting the phase selectivity of the crystallization. It thus appears that the modification of conformations of flexible organic structure-directing agents by varying the type and concentration of alkali cations may be an area of considerable possibility for finding new zeolite structures.