Premium
Benzene‐ d 6 and toluene‐ d 8 as guest molecules in micropores of a layered zirconium phosphonate: 2 H, 13 C{ 1 H}, and 31 P{ 1 H} solid‐state NMR, deuterium NMR relaxation, and molecular motions
Author(s) -
Contreras Aida R.,
Bakhmutov Vladimir I.,
Elliott Douglas W.,
Clearfield Abraham
Publication year - 2018
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4779
Subject(s) - chemistry , molecule , toluene , benzene , nmr spectra database , phosphonate , crystallography , spectral line , anisotropy , relaxation (psychology) , perpendicular , deuterium , analytical chemistry (journal) , organic chemistry , atomic physics , geometry , physics , psychology , social psychology , mathematics , quantum mechanics , astronomy
For the first time, pore spaces in the Zr (IV) phosphonate ( 1 ) as a representative of layered metal (IV) phosphonate materials have been investigated by studying mobility of guest molecules, benzene‐ d 6 , and toluene‐ d 8 . Guest molecules located in micropores of 1 have been characterized by solid‐state 13 C{ 1 H} and 2 H NMR spectra in static samples with varying temperatures. At moderately low temperatures, the benzene and toluene molecules experience fast isotropic reorientations and show the motionally averaged liquid‐like carbon and deuterium line shapes in the NMR spectra. At lower temperatures, two anisotropic motional modes have been found for benzene molecules by analyzing the 2 H NMR line shapes: the well‐known in‐plane C 6 rotation and composite motions. Interpretation of the variable‐temperature 2 H T 1 relaxation times identifies the composite motions as 120° flips around the C 6 axis perpendicular to the molecular plane and the rotations around the molecular para ‐C‐C axis. The data obtained resulted in the idealized (cylinder‐shaped) model of micropores in compound 1 with the diameter of 20–30 Å. Furthermore, the activation energy of 20.1 kJ/mol determined for the benzene motions classifies the molecule–surface interactions as weak but enough for absorption.