Characterization of a Molecule Partially Confined at the Pore Mouth of a Zeotype

Abstract

We investigate the interaction between am olecule and apore mouth-a critical step in adsorption processes-by characterizing the conformation of am acrocyclic calix-[4]arene-Ti IV complex, whichisgrafted on the external surface of az eotype (*-SVY). X-ray absorption and 13 C{ 1 H} CPMAS NMR spectroscopies independently detect aunique conformation of this complex when it is grafted at crystallographically equivalent locations that lie at the interface of 7 hemispherical microporous cavities and the external surface. Electronic structure calculations support the presence of this unique conformation, and suggest that it is brought about by as pecific orientation of the macrocycle that maximizes noncovalent interactions between calix[4]arene upper-rim tertbutyl substituents and the microporous-cavity walls.O ur comparative study provides ar are "snapshot" of am olecule partially confined at ap ore mouth, an essential intermediate for adsorption into micropores,a nd demonstrates how surrounding environment controls this confinement in asensitive fashion.