13C and 31P Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopy of Tris(2,3-naphthalenedioxy)cyclotriphosphazene Inclusion Compounds

Abstract

The inclusion compounds of tris(2,3-naphthalenedioxy)cyclotriphosphazene (TNP) with several small molecules have been studied, for the first time, by 13C magic-angle spinning (MAS) NMR. The channel-type structure of TNP inclusion compounds (ICs) with benzene (and tetrahydrofuran, THF), and the cage-type structure of TNP ICs with p-xylene has been associated with the multiplicity of the 13C signals due to each carbon atom in the unit cell. Bending of the large paddles of the TNP matrix was established on the basis of the chemical shifts. The release of the guest molecules has been followed by differential scanning calorimetry and by solid-state NMR. The 13C cross-polarization (CP) MAS spectrum of guest-free TNP structure has been interpreted in accordance with the formation of the monoclinic cell. 31P CP MAS spectra reflect the symmetry of the crystal cell. A residual dipolar coupling with 14N is also observed. The dynamic behavior of the guest and host molecules has been studied by the measument of 13C T1...