Influence of methyl and propyl groups on the vibrational spectra of two imidazolium ionic liquids and their non-ionic precursors

Autor: Hyung J. Kim, Drai Mokhtar, Mustapha Rahmouni, Boumediene Haddad, Didier Villemin, Nilesh R. Dhumal, Serge Bresson, El-habib Belarbi, Johannes Kiefer, Mimanne Goussem
Přispěvatelé: Laboratoire de chimie moléculaire et thioorganique (LCMT), Centre National de la Recherche Scientifique (CNRS)-Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Laboratoire Synthèse et Catalyse [Tiaret] (LSCT), Université Ibn Khaldoun de Tiaret = University of Tiaret
Jazyk: angličtina
Rok vydání: 2017
Předmět:
Zdroj: Journal of Molecular Structure
Journal of Molecular Structure, Elsevier, 2017, 1134, pp.582-590. ⟨10.1016/j.molstruc.2017.01.008⟩
ISSN: 0022-2860
DOI: 10.1016/j.molstruc.2017.01.008⟩
Popis: Imidazolium-based ionic liquids (ILs) are usually synthesized using non-ionic imidazole compounds as precursors. While the ILs have been extensively studied in the past, the precursors was not paid much attention to. The structural analysis of the precursors, however, may offer an opportunity to better understand the behavior of the ionic compounds of interest. In this paper, a comparative study of two ionic liquids and their imidazole precursors is presented. The precursors 1-methylimidazole [1-MIM] and 1,2-dimethylimidazole [1,2-DMIM] are compared in order to explain the influences of the methyl group at the C(2) position (methylation). Since the imidazole compounds are non-ionic, the spectroscopic properties of [1-MIM] and [1,2-DMIM] are not affected by cation-anion interactions. In addition, the products obtained by alkylation using propyl iodide leading to the corresponding IL compounds 1-methyl-3-propylimidazolium iodide [1-MPrIM + ][I − ] and 1,2-dimethyl-3-propylimidazolium iodide [1,2-DMPrIM + ][I − ] were studied. For this purpose, vibrational spectroscopy in terms of FT-Raman and FTIR in the wavenumber range from [45 to 3500 cm −1 ] and from [600 to 4000 cm −1 ], respectively, was performed. Moreover, to aid the spectral assignment, density functional theory (DFT) calculations were carried out. The aim was to investigate the vibrational structure, to understand the effects of the propyl group at the N(3) and of the methyl group at the C(2) position, and to analyze the resulting cation-anion interactions. The data indicate that the iodide ion predominantly interacts with the C(2) H group via hydrogen bonding. Upon methylation, the C(4/5) H moiety becomes the main interaction site. However, an interaction takes place only with one of the two hydrogen atoms resulting in a split of the initially degenerate CH stretching modes.
Databáze: OpenAIRE
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