title: Tetraalkylammonium salts of weakly coordinating aluminates: ionic liquids, materials for electrochemical applications and useful compounds for anion investigation.
abstract: In this study, we investigated the tetraalkylammonium salts of the weakly coordinating fluorinated alkoxyaluminates [pftb](-) ([Al(O(C(CF(3))(3))(4)](-)), [hfip](-) ([Al(OC(H)(CF(3))(2))(4)](-)) and [hftb](-) ([Al(OC(CH(3))(CF(3))(2))(4)](-)) in order to obtain information on their undisturbed spectral and structural properties, as well as to study their electrochemical behavior (i.e., conductivities in non-polar solvents and electrochemical windows). Several of the compounds qualify as ionic liquids with melting points as low as 42 degrees C for [NBu(4)](+)[hfip](-). Simple and almost quantitative metathesis reactions yielding these materials in high purity were developed. These [NR(4)](+) salts serve as model compounds for undisturbed anions and their vibrational spectra--together with simulated spectra based on quantum chemical DFT calculations--were used for the clear assignment of the anion bands. Besides, the ion volumes of the anions (V(ion)([pftb](-)) = 0.736 nm(3), V(ion)([hftb](-)) = 0.658 nm(3), V(ion)([hfip](-)) = 0.577 nm(3)) and their decomposition pathways in the mass spectrometric measurements have been established. The salts are highly soluble in non-polar solvents (up to 1.09 mol L(-1) are possible for [NBu(4)](+)[hftb](-) in CH(2)Cl(2) and 0.41 mol L(-1) for [NBu(4)](+)[hfip](-) in CHCl(3)) and show higher molar conductivities if compared to [NBu(4)](+)[PF(6)](-). The electrochemical windows of CH(2)Cl(2), CH(3)CN and 1,2-F(2)C(6)H(4) using the [NBu(4)](+) aluminate electrolytes are up to +0.5 V/-0.7 V larger than those using the standard [NBu(4)](+)[PF(6)](-).
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Institut des Sciences et Ingénierie Chimiques, EPFL-SB-ISIC-LPI, Station 6, 1015 Lausanne, Switzerland.
authors.forename: Ines
authors.initials: I
authors.lastname: Raabe
authors.forename: Katrin
authors.initials: K
authors.lastname: Wagner
authors.forename: Kristin
authors.initials: K
authors.lastname: Guttsche
authors.forename: Mingkui
authors.initials: M
authors.lastname: Wang
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.forename: Gustavo
authors.initials: G
authors.lastname: Santiso-Quiñones
authors.forename: Ingo
authors.initials: I
authors.lastname: Krossing