title: Two-dimensional ultrafast vibrational spectroscopy of azides in ionic liquids reveals solute-specific solvation.
abstract: The stereochemistry and the reaction rates of bimolecular nucleophilic substitution reactions involving azides in ionic liquids are governed by solute-solvent interactions. Two-dimensional ultrafast vibrational spectroscopy (2D-IR) shows that the picosecond dynamics of inorganic azides are substantially slower than organic azides in a series of homologous imidazolium ionic liquids. In water, both organic and inorganic azides spectrally diffuse with a ∼2 ps time constant. In the aprotic solvent tetrahydrofuran, both kinds of azides spectrally diffuse on a timescale >5 ps. In ionic liquids, like 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), organic azides spectrally diffuse with a 2-4 ps time constant, and inorganic azides spectrally diffuse with a >40 ps time constant. Such a striking difference suggests that neutral (organic) and charged (inorganic) azides are incorporated in the ionic liquids with different solvation structures.
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. sgr@pitt.edu.
authors.forename: Samrat
authors.initials: S
authors.lastname: Dutta
authors.forename: Zhe
authors.initials: Z
authors.lastname: Ren
authors.forename: Thomas
authors.initials: T
authors.lastname: Brinzer
authors.forename: Sean
authors.initials: S
authors.lastname: Garrett-Roe
mesh_terms: D001386:Azides / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D012995:Solubility; D013055:Spectrophotometry, Infrared; D013997:Time Factors; D014732:Vibration; D014867:Water / Q000737:chemistry*
chemical_list: C000597051:1-butyl-3-methylimidazolium tetracyanoborate; D001386:Azides; D007093:Imidazoles; D052578:Ionic Liquids; D009570:Nitriles; D014867:Water