Analysis of proton/fluoride spin-lattice NMR dispersion experiment of an ionic liquid, BMIM[PF6] by using molecular dynamics simulations and relaxation theory
2015 (English)Manuscript (preprint) (Other academic)
Proton/Fluoride spin-lattice nuclear magnetic relaxation dispersion(NMRD) measurements of 1-Butyl-3-methylimidazolium-hexa fluorophosphate (BMIM[PF6])have been carried out using a 1T Stelar FFC2000 fast-field-cycling instrument at proton Larmor frequencies ranging from 10 kHz to 40 MHz and at different temperatures. The NMRD profiles are interpreted by means of a simple relaxation modelbased on the inter- and intra-molecular dipole dipole relaxation mechanims. Using an atomic and a coarse-grained (CG)Molecular Dynamics (MD) simulations at temperature 323 K the relevant dipole-dipole correlation functions are calculated. The result indicate that the NMRD profiles can be rationalized using a combination of intra and inter molecular dipole-dipole couplings. However, both are mainly modulated by molecular reorientation whereas translation diffusion plays a minor role. The molecular reorientation dynamics of BMIM[PF6] ,BMIM+ ion are in the nano secondtime regime whereas the reorientation of [PF6]- is much faster and loses its correlation in the ps regime. The relaxation mechanism for [PF6]- is H-F inter-molecular dipole-dipole coupling which is modulated by the reorientation of the H-containing molecule.
Place, publisher, year, edition, pages
proton, fluoride, spin-lattice, relaxation, ionic liquid, MD, BMIM[PF6]
Research subject Physical Chemistry
IdentifiersURN: urn:nbn:se:umu:diva-110719OAI: oai:DiVA.org:umu-110719DiVA: diva2:865044
2015, in manuscript2015-10-262015-10-262015-11-11