Synthesis, thermal properties, vibrational spectra and computational studies of Trioctylmethylammonium bis(trifluoromethylsulfonyl)imide ionic liquid

Abstract

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Experimental and DFT studies on structure, spectroscopic and thermal properties of N-Methyl-N,N,N-trioctylammonium chloride ionic liquid

“…The interesting physicochemical properties and applications that present the ionic liquids (ILs) have allowed the gradual growth in the investigations of these species from different points of view [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. For instance, the quaternary ammonium salt, known as Aliquat 336, presents characteristics properties and major applications [15][16][17][18][19][20]. Besides, the synthesis reactions of these ionic liquids are environmentally benign and friendly due to its stability against air and moisture and; in addition, these salts are easy to handle [16,17,20].…”

“…Hence, the cation-anion interactions play a very important role in the properties of ILs [4,5,9,12]. Currently, the elucidations of all types of interactions in ILs are carried out combining theoretical calculations with different spectroscopic techniques [9,12,14,15]. So far, various quaternary ammoniums ILs with different cations and anions have been reported for Aliquat 336, including a recent study on the synthesis and structural and thermal properties of [Aliquat + ][NTF 2 -] IL [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] but the structural, electronic, vibrational and topological properties of [Aliquat + ][Cl -] IL was no reported yet.…”

“…So far, various quaternary ammoniums ILs with different cations and anions have been reported for Aliquat 336, including a recent study on the synthesis and structural and thermal properties of [Aliquat + ][NTF 2 -] IL [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] but the structural, electronic, vibrational and topological properties of [Aliquat + ][Cl -] IL was no reported yet. Hence, the aims of this work are: (i) to optimize the structure of [Aliquat + ][Cl -] IL in order to predict structural, electronic, topological and vibrational properties, (ii) to find the coordination mode between cation and anion by using natural bond orbital (NBO) and atoms in molecules (AIM) calculations, (iii) to characterize experimentally [Aliquat + ][Cl -] IL by using the infrared, Raman, 1 H-and 13 C-NMR spectra and, (vi) to perform comparisons of this IL with the reported for [Aliquat + ][NTF 2 -] IL [15]. In this work, the experimental infrared (FTIR/ATR) and Raman spectra of [Aliquat + ][Cl -] IL were recorded and its structure in gas phase was optimized by using the B3LYP/6-31G* method [32,33].…”

“…The combinations of vibrational spectra with the DFT calculations and the scaled mechanical force field (SQMFF) methodology have allowed the determination of harmonic force field and the scaled force constants [34][35][36]. The normal internal coordinates for the cation were taken of those proposed for [Aliquat + ][NTF 2 -] IL [15] while the used transferable scaling factors were those recommended for the method employed by Rauhut and Pulay [35]. The investigations of reactivity and behaviours of [Aliquat + ][Cl -] IL were evaluated taking into account the frontier orbitals and some interesting descriptors [9,12,15].…”

“…The normal internal coordinates for the cation were taken of those proposed for [Aliquat + ][NTF 2 -] IL [15] while the used transferable scaling factors were those recommended for the method employed by Rauhut and Pulay [35]. The investigations of reactivity and behaviours of [Aliquat + ][Cl -] IL were evaluated taking into account the frontier orbitals and some interesting descriptors [9,12,15]. Then, all obtained properties were compared with compounds with similar cations [15] while the complete assignments of 237 vibration modes expected for [Aliquat + ][Cl -] IL were reported for first time in the present work.…”