Intermolecular Interactions of Xe Atoms Confined in One-dimensional Nanochannels of Tris(o-phenylenedioxy)cyclotriphosphazene as Studied by High-pressure ¹²⁹Xe NMR

Abstract

The pressure dependence of the 129 Xe chemical shift tensor confined in the Tris(o-phenylenedioxy) cyclotriphosphazene (TPP) nanochannel was investigated by high-pressure 129 Xe NMR spectroscopy. The observed 129 Xe spectrum in the one-dimensional TPP nanochannel (0.45 nm in diameter) exhibits a powder pattern broadened by an axially symmetric chemical shift tensor. As the pressure increases from 0.02 to 7.0 MPa, a deshielding of 90 ppm is observed for the perpendicular component of the chemical shift tensor δ ⊥ , whereas a deshielding of about 30 ppm is observed for the parallel one, δ . This suggests that the components of the chemical shift tensor, δ and δ ⊥ , are mainly dominated by the Xe-wall and Xe-Xe interaction, respectively. Furthermore, the effect of helium, which is present along with xenon gas, on the 129 Xe chemical shift is examined in detail. The average distance between the Xe atoms in the nanochannel is estimated to be 0.54 nm. This was found by using δ ⊥ at the saturated pressure of xenon, and comparing the increment of the chemical shift value in δ ⊥ to that of a β -phenol/Xe compound.

Preparation and Characterization of New Inclusion Compounds Using Stable Nitroxide Radicals and an Organic 1-D Nanochannel as a Template

“…The crystal of tris( o -phenylenedioxy)cyclotriphosphazene (TPP, Scheme 1 a) [ 1 , 2 , 3 , 4 ] has a one-dimensional (1-D) homogeneous nanochannel [ 5 , 6 , 7 ]. In recrystallization of TPP, solvent molecules are included in the nanochannel.…”

ESR study of molecular dynamics and orientation of TEMPO included in organic 1-D nanochannel

“…In addition, the nanochannel is highly homogeneous, as revealed mainly by 129 Xe NMR. [8][9][10] These features are feasible to include the guest molecule 1-Dly. Therefore, this organic zeolite is expected to be a template to produce novel 1-D functional materials.…”

Preparation and Characterization of Inclusion Compounds Using TEMPOL and an Organic 1-D Nanochannel as a Template

“…Although the nanochannel of TPP is homogeneous, as revealed by 129 Xe NMR results [7][8][9], in fact, channel wall irregularities exist because of the repetition of the phenyl ring moiety. The bottleneck gives the minimum diameter, which corresponds to the diameter of a circle close to the plane of the phenyl rings.…”

“…Since the channel wall comprises phenyl rings of TPP molecules, in which the ring plane is parallel to the channel axis, the p electrons are rich on the channel surface. The channel surface homogeneity has been defined well using 129 Xe nuclear magnetic resonance (NMR) spectroscopy [7][8][9]. TPP nanochannels show a strong affinity for including simple-shaped gas molecules, and aliphatic or aromatic molecules [6,[10][11][12].…”