posters 5th Asia-Pacific NMR Symposium 2013

“Dry Proton” Transport Behavior in the Triflic Acid Containing Guanidinium Triflate (#235)

Haijin Zhu 1 , Usman Ali Rana 2 , Vijayraghavan Ranganathan 3 , Luke A O'dell 1 , Douglas R MacFarlane 3 , Maria Forsyth 1
  1. Deakin, Waurn Ponds, VIC, Australia
  2. Sustainable Energy Technologies Center, King Saud Univerity, Riyadh, Kingdom of Saudi Arabia
  3. Department of Chemistry and the ARC Centre of Excellence for Electromaterials Science, Monash University, Melbourn

In our recent work, we have investigated the avenue of proton conductivity in the aprotic versions of organic ionic plastic crystals (OIPCs) by adding acids of various strengths and compositions.1, 2  High proton conductivity was achieved in the plastic crystal phase of various acid-containing OIPCs. In line with the emergence of these new proton-conducting materials, there is an increasingly urgent need to fully understand the nature and mechanisms of the ionic transport and related molecular dynamics in these materials. In the present work, we investigate the solid-state dynamics of a protic organic solid which we hypothesised may display OIPC behaviour, guanidinium triflate. Several orders of magnitude enhancement of conductivity is observed upon addition of HTf to the organic solid, and this appears to follow percolation behaviour with a percolation threshold of approximately 2% HTf. The data support a structural diffusion (or Grotthus) mechanism of proton transport with a calculated Haven ratio significantly less than unity. 13C SUPER and 14N overtone NMR experiments were used to study the mobility and symmetry of the triflate anion and guanidinium cation respectively at molecular level. The former experiments shows that the CF3 group in the anion displays fast and isotropic motion at room temperature. In contrast to the high mobility of the anion group, the 14N overtone experiments indicate that, the guanidinium cation is static in both the pure and the doped GTf samples at room temperature. 

  1. Rana, U. A.; Vijayaraghavan, R.; MacFarlane, D. R.; Forsyth, M. Journal of Materials Chemistry 2012, 22, 2965.
  2. Rana, U. A.; Vijayaraghavan, R.; MacFarlane, D. R.; Forsyth, M. Chemical Communications 2011, 47, 6401.