title: Development of cation/anion "interaction" scales for ionic liquids through ESI-MS measurements.
abstract: Electrospray ionization mass spectrometry applied to ionic liquids allowed the study of loosely bonded supramolecules, originating from these organic salts. Based on the observation that ionic liquids formed cationic [C(q+1)X(q)](+) and anionic [C(q)X(q+1)](-) supramolecular aggregates, we have investigated mixed networks, formed by different cations coordinated to a selected anion or by different anions bonded to a given cation, i.e., [C1...X...C2](+) and [X1...C...X2](-), with the aim to build a scale of the cation-anion interaction strength. The qualitative order of intrinsic bond strength to Br- was found to be the following: [emim](+) > [bmim](+) > [mor1,2](+) > [hmim]+ > [omim](+) > [mor1,4](+) > [bupy](+) > [bpyrr](+) > [picol](+) > [bm(2)im](+) > [TBA](+). Similarly, the interaction energies to 1-butyl-3-methylimidazolium (bmim) species envisaged two classes of anions: species tightly coordinated to the cationic moiety that include CF3COO(-), Br(-), N(CN)2(-), and BF4(-) and anions loosely interacting with the alkylimidazolium species such as OTf(-), PF6(-), and Tf2N(-).
authors.affiliation: Dipartimento di Chimica Bioorganica e Biofarmacia, via Bonanno 33, 56126 Pisa, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Bini
authors.forename: Olga
authors.initials: O
authors.lastname: Bortolini
authors.forename: Cinzia
authors.initials: C
authors.lastname: Chiappe
authors.forename: Daniela
authors.initials: D
authors.lastname: Pieraccini
authors.forename: Tiziana
authors.initials: T
authors.lastname: Siciliano
mesh_terms: D000838:Anions / Q000737:chemistry; D001965:Bromides / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D008055:Lipids / Q000737:chemistry*; D008958:Models, Molecular; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000838:Anions; D001965:Bromides; D002412:Cations; D008055:Lipids