Cation and Anion Transport in a Dicationic Imidazolium-Based Plastic Crystal Ion Conductor
School of Science
Journal of Physical Chemistry B
Here we investigate the organic ionic plastic crystal 1,2-bis[N-(N′-hexylimidazolium-d2(4,5))]ethane 2PF6– in one of its solid plastic crystal phases by means of multinuclear solid-state (SS) NMR and pulsed-field-gradient NMR diffusometry. We quantify distinct cation and anion diffusion coefficients as well as the Arrhenius diffusion activation energies (Ea) in this dicationic imidazolium-based plastic crystal. Our studies suggest a change in transport mechanism for the cation upon varying thermal and magnetic treatment (9.4 T), evidenced by differences in cation and anion Ea. Moreover, variable temperature 2H SSNMR line shapes support a change in local molecular environment upon slow cooling in B0. We quantify the percentage of mobile anions as a function of temperature with 19F SSNMR, wherein two distinct spectral features are present. We also comment on the Arrhenius pre-exponential factor for diffusion (D0), giving insight into the number of degrees of freedom for transport for both cation and anion as a function of thermal treatment. Given the breadth and depth of our measurements, we propose that bulk ion transport is dominated by anion diffusion in ionic-liquid-like domain boundaries separating crystallites. This study elucidates fundamental properties of this plastic crystal, and allows for a more general and deeper understanding of ion transport within such materials.
SMC Affiliated Work
Mark Lingwood (Chemistry): “Cation and Anion Transport in a Dicationic Imidazolium-Based Plastic Crystal Ion Conductor,” with Bryce E. Kidd, Minjae Lee, Harry W. Gibson, and Louis A. Madsen, in Journal of Physical Chemistry B. (2014), 118 (8), pp 2176–2185. DOI:10.1021/jp4084629
Kidd, Bryce E.; Lingwood, Mark; Lee, Minjae; Gibson, Harry W.; and Madsen, Louis A.. Cation and Anion Transport in a Dicationic Imidazolium-Based Plastic Crystal Ion Conductor (2014). Journal of Physical Chemistry B. 118 (8), 2176-2185. 10.1021/jp4084629 [article]. https://digitalcommons.stmarys-ca.edu/school-science-faculty-works/78