title: A Reinvestigation of the Ionic Liquid Diisopropylethylammonium Formate by NMR and DFT Methods.
abstract: The complex between diisopropylethylamine (DIPEA) and formic acid has been reinvestigated. Mixing the compounds in the ratio 1:1 leads to a phase separation in which the upper phase is DIPEA and the lower phase is the "ionic liquid" named DIPEF. A combined NMR and DFT study shows that the lower phase primarily is formic acid:formate and diisopropylammonium ions in the ratio 2:1 (acid:base) plus the formic acid dimer. Addition of more acid leads to more and more of the acid dimer. The proton transfer in the system is 65-80%. The structural picture presented in this paper is very different from that presented elsewhere. However, the present picture should be considered using acids and bases with a pKadifference less than 8. The formic acid content in the DIPEF ionic liquid causes desorption of the dye-sensitized solar cell (DSC) dye N719 from the photo anode, and DIPEF is therefore not a suitable electrolyte for DSCs.
authors.affiliation: Department of Science and Environment, Roskilde University , DK-4000 Roskilde, Denmark.
authors.forename: Poul Erik
authors.initials: PE
authors.lastname: Hansen
authors.affiliation: Department of Science and Environment, Roskilde University , DK-4000 Roskilde, Denmark.
authors.forename: Torben
authors.initials: T
authors.lastname: Lund
authors.affiliation: Department of Science and Environment, Roskilde University , DK-4000 Roskilde, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Krake
authors.affiliation: Department of Science and Environment, Roskilde University , DK-4000 Roskilde, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Spanget-Larsen
authors.affiliation: Department of Science and Environment, Roskilde University , DK-4000 Roskilde, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Hvidt