Synthesis and characterization data of monocationic and dicationic ionic liquids or molten salts

Data presented in this article are related with the research paper entitled “Ecotoxicity assessment of dicationic versus monocationic ionic liquids as a more environmentally friendly alternative” [1]. The present article describes the synthesis steps and characterization data of a set of twenty-six imidazolium, pyrrolidinium and pyridinium-based ionic liquids (ILs) or molten salts: nine monocationic and seventeen dicationic. Specifically, the chemical structure of the compounds was confirmed by 1H NMR, 13C NMR and 19F NMR spectroscopy and mass spectrometry (MS). Other data such as physical state at room temperature, melting point temperature (for solids at room temperature) and thermal decomposition temperature (when melting was not reached before decomposition) of the ILs or molten salts are also reported here.


a b s t r a c t
Data presented in this article are related with the research paper entitled "Ecotoxicity assessment of dicationic versus monocationic ionic liquids as a more environmentally friendly alternative" [1]. The present article describes the synthesis steps and characterization data of a set of twenty-six imidazolium, pyrrolidinium and pyridinium-based ionic liquids (ILs) or molten salts: nine monocationic and seventeen dicationic. Specifically, the chemical structure of the compounds was confirmed by 1 H NMR, 13 C NMR and 19 F NMR spectroscopy and mass spectrometry (MS). Other data such as physical state at room temperature, melting point temperature (for solids at room temperature) and thermal decomposition temperature (when melting was not reached before decomposition) of the ILs or molten salts are also reported here.

Value of the Data
All the steps for the synthesis of the ILs or molten salts here described and the methods can be followed by other researchers.
The chemical synthesis of some of these ILs or molten salts had not been reported before. NMR spectra and MS data of the ILs or molten salts synthesized are useful for structural characterization of these and other similar ILs or molten salts.
Data on melting point and decomposition temperature of these ILs or molten salts can be valuable for the design of their applications.

Data
The abbreviations, molecular weights and structures of the ILs or molten salts are presented in Table 1. The synthesis steps necessary for the preparation of the ILs or molten salts are described then in detail. After the report of the chemical synthesis of the ILs or molten salts, their characterization (NMR spectra and MS) is included. Figs. 1-20 show the 1 H NMR and 13 C NMR spectra of the novel compounds. Finally, Table 2 collects the physical state of the ILs or molten salts at room temperature, their colour, melting point (for solids at room temperature) and decomposition temperature (when melting is not reached before thermal decomposition).

Experimental design, materials, and methods
See Table 1 3. Synthesis and characterization of ILs C 8 (MIm)Br was synthesized following procedures described in the literature with modifications [2,3]. 100 mmol of 1-methylimidazole was placed in a round bottom flask fitted with a reflux condenser and an additional funnel under a static atmosphere of Ar. 110 mmol of 1-bromooctane was added dropwise via a pressure equalising addition funnel while the mixture was stirred at 60°C under inert atmosphere. The additional funnel was removed and the reaction mixture was stirred at  [4]. C 8 (MPyrr)Br and C 8 (Pyr)Br were synthesized according to procedures described in the literature [5]. 240 mmol of 1-methylpyrrolidine or pyridine was placed in a round bottom flask fitted with a water condenser topped with a drying tube (CaCl 2 ) to avoid moisture penetration. 288 mmol of 1-bromooctane was added dropwise while stirring at 70°C. The reaction time was 48 hours. The desired product was recrystallised in acetonitrile/ethyl acetate ( E1:3 v:v) and dried first using a rotary evaporator and then under high vacuum (p o 10 À 2 mbar) at 60°C for 12 h to yield a white solid. Data in agreement with the literature [6,7]. C 8 (MIm)NTf 2 , C 8 (MPyrr)NTf 2 and C 8 (Pyr)NTf 2 were synthesized according to procedures described in the literature [5,8,9]. 5 mmol of C 8 (MIm)Br, C 8 (MPyrr)Br or C 8 (Pyr)Br were transferred to a round bottom flask and dissolved in 10 mL of ultrapure water while stirring at room temperature. Aqueous lithium bis(trifluoromethane)sulfonylimide (6 mmol in 6 mL of ultrapure water) was added dropwise. The mixture was stirred at room temperature for 24 hours. Then the mixture was transferred to a funnel washing with ethyl acetate; the aqueous layer was separated and the ionic liquid dissolved in 30 ml of ethyl acetate and washed with ultrapure water (4 Â 30 mL). Finally, the ethyl acetate was removed in a rotary evaporator and the ionic liquid was dried under vacuum (p o 10 À 2 mbar) at 60°C for 24 hours. Data in agreement with the literature [8,10,11]. C 8 (MIm)SbF 6 , C 8 (MPyrr)SbF 6 and C 8 (Pyr)SbF 6 were synthesized according to procedures described in the literature [12]. In a single necked round bottom flask with a magnetic stirring bar, 5 mmol of C 8 (MIm)Br, C 8 (MPyrr)Br or C 8 (Pyr)Br was dissolved in 20 mL of dichloromethane. Then 6 mmol of sodium hexafluoroantimonate (V) was added. The mixture was stirred for 24 hours at room temperature while observing the formation of a white solid (NaBr). This solid was filtered off and the filtrate was washed with ultrapure water several times (5 Â 50 mL). The solvent was removed in a rotary evaporator and the ionic liquid was dried under high vacuum (p o 10 À 2 mbar) at 70°C for 24 hours. Data in agreement with the literature [13]. C 2 (MIm) 2 Br 2 , C 3 (MIm) 2 Br 2 , C 4 (MIm) 2 Br 2 , C 6 (MIm) 2 Br 2 and C 8 (MIm) 2 Br 2 were synthesized following the same procedure [8,14,15]. A three-necked round bottom flask fitted with reflux condenser and pressure equation funnel was filled with a solution of 30 mmol of 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane, 1,6-dibromohexane or 1,8-dibromooctane in 12 mL of methanol. Then 60 mmol of 1-methylimidazole was added dropwise while stirring at room temperature. The resulting mixture was further heated and stirred at 40-50°C for 48 hours. The product was isolated by filtration and purified by recrystallization. The resulting product was transferred to a single-necked round-bottomed flask, washing with methanol. The solvent was then removed under reduced pressure using a rotary evaporator. Data in agreement with the literature [15][16][17][18].  C 3 (MPyrr) 2 Br 2 , C 4 (MPyrr) 2 Br 2 , C 6 (MPyrr) 2 Br 2 and C 8 (MPyrr) 2 Br 2 were synthesized with the same procedure [15,19]. A three-necked round-bottomed flask fitted with a reflux condenser and pressure-equalised funnel was charged with a solution of 30 mmol of 1,3-dibromopropane, 1,4-dibromobutane, 1,6-dibromohexane or 1,8-dibromooctane in 10 ml of methanol. Then 63 mmol of 1-methylimidazole was added dropwise while stirring at room temperature. The resulting mixture was further heated and stirred at 40-50°C for 48 hours. The product was isolated by filtration and  purified by recrystallization in methanol/ethyl acetate ( E1:3 v:v). The resulting product was transferred to a single-necked round-bottomed flask, washing with methanol. The solvent was then removed under reduced pressure using a rotary evaporator. Data in agreement with the literature [15,18]. C 2 (Pyr) 2 Br 2 , C 3 (Pyr) 2 Br 2 , C 4 (Pyr) 2 Br 2 , C 6 (Pyr) 2 Br 2 , C 8 (Pyr) 2 Br 2 and C 12 (Pyr) 2 Br 2 were synthesized with the same procedure [15]. A three-necked round bottomed flask fitted with a reflux  condenser and pressure-equalised addition funnel was charged with a solution of 30 mmol of 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane, 1,6-dibromohexane, 1,8-dibromooctane or 1,12-dibromododecane in 5 mL of methanol. Then 75 mmol of 1-methylimidazole was added dropwise while stirring at room temperature. The resulting mixture was further heated and stirred at 50°C for 48 hours. The product was isolated by filtration and purified by recrystallization in methanol/ethyl acetate (E1:3 v:v). The resulting product was transferred to a single-necked round-  bottomed flask washing with methanol. The solvent was then removed under reduced pressure using a rotary evaporator. Data in agreement with the literature [15].
1-(3-bromopropyl)pyridinium bromide was synthesized following the procedure described in the literature [20]. 100 mmol of pyridine was transferred to a round bottom flask. 150 mmol of 1,3-dibromopropane was added and the resulting mixture was stirred for three days at room  temperature. Then, the mixture was washed with ethyl acetate to remove any unreacted reactants and filtered to obtain a white precipitate. C 3 (Pyr) (MIm) Br 2 and C 3 (Pyr) (MPyrr) Br 2 were synthesized with the same procedure [20]. A three-neck round bottom flask fitted with a reflux condenser was charged with a solution of 15 mmol of (3-bromopropyl)pyridinium bromide in 20 mL of methanol. Then 18 mmol of 1-methylimidazole or  19.5 mmol of 1-methylpyrrolidine was added dropwise while stirring at room temperature. The resulting mixture was refluxed while stirring at 50°C for 48 hours. The resulting solution was recrystallised directly from methanol/ethyl acetate (E1:5 v:v) and the product was isolated by filtration.  The structures of the resulting ILs were confirmed by 1 H, 13 C and 19 F NMR spectroscopy (recorded generally at room temperature on a Jeol model EX270) and mass spectrometry (Bruker MicroTOF 61 spectrometer).