Structural and conformational properties of the quaternary ammonium ionic liquid N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium iodide

We have used single-crystal X-ray structural analysis and Raman spectroscopy to study the crystalline structure and conformational properties of a quaternary ammonium ionic liquid, N,N-diethyl-Nmethyl-N-(2-methoxyethyl) ammonium iodide ([DEME][1]). At 296 K the crystal structure of [DEME][I] was determined to be monoclinic (P2(1)/a, Z=8) with a = 13.216 (5), b = 12.842 (3), c = 14.417 (6), beta = 104.10 (3)degrees, and V = 2373.1 (15) angstrom(3). With results from X-ray diffraction measurements and density functional theory calculations, we have identified two folded forms: Gauche(-)-Gauche(-)-gauche(-)-gauche(-)-trans and Gauche(+)-Gauche(+)-gauche(+)-gauche(+)-trans conformers, having intramolecular attractive N+...O- interactions of [DEME](+) in the single-crystal state. In the liquid state, [DEME](+) exists in equilibrium between folded and (non-interacting) extended forms. (C) 2013 Elsevier B.V. All rights reserved.