Study of molecular dynamics and cross relaxation in tetramethylammonium hexafluorophosphate (CH3)4NPF6 by 1H and 19F NMR

Abstract

a b s t r a c t (CH 3 ) 4 NPF 6 is studied by NMR measurements to understand the internal motions and cross relaxation mechanism between the heterogeneous nuclei. The spin lattice relaxation times (T 1 ) are measured for F NMR results are attributed to cross relaxation between proton and fluorine and motional parameters for the PF 6 group reorientation are evaluated.

1H and 19F NMR relaxation time studies in (NH4)2ZrF6 superionic conductor

“…Several authors have observed a similar behavior in a number of compounds, for example, Watton et al [22] in (NH 4 ) 2 TiF 6 and McDowell et al [34] in (CH 3 ) 3 NPF 5 , and have explained their results in a similar manner. We have recently [35] observed a similar cross relaxation between 1 H and 19 F in (CH 3 ) 4 NPF 6 . Indeed, in the present compound, Kavun et al [11] have also observed that the 19 F second moment reaches the rigid lattice limit at a much higher temperature of about 250 K. Figure 4 shows fitting of Eq.…”

A Comparative Study of the Rotational Dynamics of PF6– Anions in the Crystals and Liquid States of 1-Butyl-3-methylimidazolium Hexafluorophosphate: Results from 31P NMR Spectroscopy

“…The dynamical behavior of the constituent ions is central in controlling the physical state and properties of these materials. Therefore, a fundamental mechanistic understanding of the PF 6 – rotational dynamics in the solid state for alkali salts, − ammonium salts, − and the other complex salts − has been the subject of intense investigation in the literature. As might be expected, the PF 6 – rotational dynamics depend on temperature as well as on the chemistry, structure, and phase state of the material in question.…”

“…68 It is intuitively expected and was suggested in a number of previous studies that the ionic volume or radius is roughly correlated with PF 6 − rotational dynamics. 2,5,14,23 This is because larger ionic volume can decrease cation−anion interaction that could result in faster PF 6 − rotational dynamics. However, the data in Figure 6 indicate almost no relationship between the ionic volume and the dynamical parameters for the PF 6 − rotational dynamics.…”