- Email: [email protected]
Low viscosity azide-containing mono and dicationic ionic liquids with unsaturated side chain
Low viscosity azide-containing mono and dicationic ionic liquids with unsaturated side chain Reza Fareghi-Alamdari, Razieh Hatefipour PII: DOI: Reference:
S0167-7322(15)31022-9 doi:10.1016/j.molliq.2016.11.006 MOLLIQ 6547
To appear in:
Journal of Molecular Liquids
Received date: Revised date: Accepted date:
9 November 2015 11 August 2016 2 November 2016
Please cite this article as: Reza Fareghi-Alamdari, Razieh Hatefipour, Low viscosity azide-containing mono and dicationic ionic liquids with unsaturated side chain, Journal of Molecular Liquids (2016), doi:10.1016/j.molliq.2016.11.006
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Low Viscosity Azide-Containing Mono and Dicationic Ionic Liquids with Unsaturated Side Chain
PT
Reza Fareghi - Alamdaria, Razieh Hatefipoura a Faculty of Chemistry and Chemical Engineering, Malek - Ashtar University of Technology, Tehran, Iran.
RI
Abstract
TE
D
MA
NU
SC
A new class of azide-functionalized monocationic and unsymmetrical dicationic ionic liquids (ILs) with low viscosity and high liquid range was synthesized. All of the synthesized ILs, were characterized by FT-IR, 1HNMR, 13CNMR spectroscopies and elemental analysis. Some thermophysical properties including melting point, density, shear viscosity, decomposition temperature and heat capacity of the unsymmetrical dicationic azide functionalized IL with dicyanamide (DCA) were measured. To find the unique and general features of this dicationic IL, its properties were compared with the ones of the similar monocationic ILs. The results showed that the shear viscosity, density, thermal stability and heat capacity of the unsymmetrical dicationic IL are higher than monocationic analogues. In addition we found that the shear viscosity for the synthesized unsymmetrical dicationic IL containing azide group and DCA anion is 83.9 cP whereas the shear viscosities for other dicationic ILs reported in the literature are higher than 240 cP.
AC CE P
Keywords: Ionic liquid; Azide group; Dicyanamide; Shear viscosity; Thermogravimetric analysis. 1. Introduction
In recent years, ionic liquids (ILs) have attracted much attention owing to their unique physicochemical properties. Their properties can be varied to some extent for specific applications by changing the anions, cations or alkyl substituents of the cations. The notable characteristics of ILs are their non-measurable vapor pressure, high thermal stability, wide liquid range and solvating properties for diverse kinds of materials. Because of these particular properties, ILs have brought a green revolution in chemistry and chemical engineering in the past dozen years. Researches and developments that involve ILs are prevalent in nearly every branch of chemistry and material science, including catalysis [1- 4], organic synthesis [5- 7], separation and analysis [8, 9], electrochemistry [10- 13], material chemistry [14- 17], and energy technology [18, 19]. Moreover certain ILs do behave as fuels and energetic materials [20, 21]. In development of new high-performance energetic materials, nitrogen-rich ILs represent an individual class of energetic molecular frameworks, which have recently attracted significant interest in the design of energetic materials due to their high heats of formation, density, and thermal stability. These energetic ionic liquids (EILs) are most often composed of high nitrogen
Corresponding authors: Fax: +98-21-44658251; Tel: +98-937-3381632. E-mail: [email protected]
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
organic cations (e.g., tetrazolium [22], triazolium [23], guanidinium [24], and imizadolium [25]) and bulky anions with one or more energetic groups such as −NO2, −N3 and –CN. Recently some reports about the development and preparation of energy-rich compounds which contain organic azide groups have appeared [24, 26]. Each azide group adds approximately 280 KJ.mol-1 to the energy content of molecule [27]. Among ILs, azide containing ILs are thermally stable and have significantly reduced sensitivity and toxicity characteristics because having negligible vapor pressure [27]. The most importance of the EILs, is their application as liquid fuel in bipropellant systems. In these systems, spontaneous reaction occurs when the fuel and oxidizer are contacted together. It is desirable for these reactions to proceed as rapidly as possible [28]. The fuel of a bipropellant must be a compound with a wide liquid range and low melting point. Additionally, for propellant applications, fuels with low viscosities are highly desirable because the low viscosity can facilitate rapid mixing of IL as fuel with the oxidizer and therefore encourage rapid initiation processes [29]. In the cases of imidazolium based ILs, it has been shown that employing the proper alkyl chains or introducing specified functional groups can decrease the viscosity. Also it seems that the anion structure of EILs has an obvious effect on the viscosity. The combination of the dicyanamide (DCA) anion with imidazolium-based cations, can favor the formation of slightly viscous EILs [20]. Nowadays, the search for new ILs with low viscosities has also been a hot topic in the fields of EILs. We report here, several new series of mono and dicationic imidazolium based ILs containing an azide group. Since DCA anion is expected to decrease melting point and viscosity and increase thermal stability of ILs [30], this anion was chosen to design the structure of desired ILs. All of the synthesized ILs were liquid at room temperature. Density, melting point and some thermophysical properties including shear viscosity, heat capacity and decomposition temperature of the synthesized ILs containing azide functionality with DCA, were studied.
2. Experimental
2.1. Materials and instruments
All of the solvents and chemicals were purchased from Sigma-Aldrich chemical company and were used without further purification. 1H and 13CNMR spectra were recorded on a Brucker Avance DRX – 500 MHz spectrometer, in CDCl3 or D2O. TMS was used as an internal standard. FT-IR spectra were recorded on a Nicolet 800 instrument. Elemental analyses were conducted using Heraeous CHN analyzer (Germany) instrument. Water content was eliminated in a treatment before the measurements of densities and viscosities that consisted of isothermal heating at 378 K for 0.5 h. This was found to be the optimal condition for removing all water presented in the ILs matrix. To prevent water absorption, all ILs were stored in a desiccator and handed inside a glovebox under an inert atmosphere of dry nitrogen. The water content of the ILs was determined by means of Mettler DL-18 Karl-Fischer titration, and the water content in synthesized ILs ranged from 0.002 to 0.006 w/w. The melting point of synthesized ILs and the heat capacity of the unsymmetrical dicationic IL were measured using a differential scanning calorimeter (DSC) in a Perkin Elmer instrument (Pyris 6 DSC model) in a nitrogen atmosphere
ACCEPTED MANUSCRIPT
MA
NU
SC
RI
PT
with a temperature rate of 20 K.min-1. The measurements were carried out using (9±1) mg of sample. The melting transition (T=429.31 K, 3.296 kg.mol-1) of the standard indium sample was used in order to calibrate temperature and energy. The zero-heat flow producer described by TA instruments was flowed for heat capacity measurements using a synthetic sapphire sample as the reference compound. All these experiments allowed estimating an overall uncertainty of ±0.1 K in temperature and ±3% in the heat capacities. Density was measured at room temperature using a Micromeritics Accupyc 1330 gas pycnometer, whereas viscosities, η, were analyzed using Anton Paar MCR 300 rheometer with a cp 25-2 fixture (25 mm diameter, 2° cone angle). Viscosity measurements were carried out at atmospheric pressure and temperature range of 298 to 373 K. The estimated uncertainty of measured densities is ±5×10-3 g.cm-3. The relative uncertainty in the dynamic viscosity was ±1.1%, whereas the uncertainty in temperature was within ±0.1 K. Thermogravimetric analysis (TGA) was conducted using a thermal analysis instrument Perkin Elmer (Pyris Diamond model) in a nitrogen atmosphere. In this method, the temperature range was between 298 and 1273 K at a heating rate of 10 K.min-1. Runs were carried out in 40 μL alumina pans and under an inert atmosphere of nitrogen. Nitrogen flow was 20 mL.min-1. Initial mass introduced in to the pan was set to (10±1) mg. 2.2. Synthesis and characterization of mono and dicationic ILs
AC CE P
TE
D
The synthesis routes for the preparation of imidazolium based ILs are shown in scheme 1. In this research some monocationic ILs (1a, 2a, 4a, 5a, 1b, 2b, 4b, and 5b) and two novel unsymmetrical dicationic azide functionalized ILs (3, 6) were synthesized. Molecular structures of all of the synthesized ILs were characterized via FT-IR, 1HNMR, 13CNMR spectroscopies and elemental analysis. All the data of characterizations are in accordance with the expected compositions and structures.
ACCEPTED MANUSCRIPT R1 N
N +
Br
Solvent free
R1=
1a: methyl 1b: R1= vinyl
Br
Br
R1=
2a: methyl 2b: R1= vinyl
N3 N
Solvent free 80 °C, 48h
AgN(CN)2
AgN(CN)2
H2O, 40 °C, 24h
H2O, 40 °C, 24h
R1 N
N
Br N(CN)2
R1=
5a: methyl 5b: R1= vinyl
TE
4a: R1= methyl 4b: R1= vinyl
D
N(CN)2
N
N R2
3: R1, R2 = methyl, vinyl
AgN(CN)2 H2O, 40 °C, 24h
N3
R1 N
N 2Br
NU
Br
R1 N
N
RI
CH3NO2, 20°C
R1 N
N R2
SC
N
N
MA
R1 N
N3
BrN3
PT
80 °C, 24h
N3 R1 N
N
N
N R2
2N(CN)2 6: R1, R2 = methyl, vinyl
AC CE P
Scheme 1. Synthesis routes of mono and diatonic ionic liquids. 2.2.1. Synthesis of 1-allyl-3-methylimidazolium bromide (1a) 1-Methylimidazole (10 mmol, 0.82 g) was mixed with allyl bromide (10 mmol, 0.86 mL), and stirred at 353 K for 24 h. The viscose product was washed three times using n-hexane to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, a brown, slightly viscous liquid was obtained. 1 H NMR (500 MHz, CDCl3) δ (ppm) = 10.33 (s, 1H; NCHN), 7.55 (s, 1H; CH(ring)), 7.39 (s, 1H; CH(ring)), 5.78-6.05 (m, 1H; CH2CHCH2), 5.45 (d, J= 17.0 Hz, 1H; CH2CHCH2(trans)), 5.42 (d, J= 10.1 Hz, 1H; CH2CHCH2(cis)), 4.97 (d, J= 6.4 Hz, 2H; NCH2CHCH2), 4.08 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 136.4, 130.2, 123.8, 122.1, 122.0, 51.6, 36.7. FTIR (KBr, ν/cm-1): 3084, 2857, 1625, 1573, 1448, 1312, 1167, 948, 843, 761, 760. Anal. Calcd. for C7H11N2Br: C, 41.40; H, 5.46; N, 13.79%. found: C, 41.38; H, 5.41; N, 13.68%. 2.2.2. Synthesis of 1-allyl-3-vinylimidazolium bromide (1b) 1-Vinylimidazole (10 mmol, 0.94 g) was mixed with allyl bromide (10 mmol, 0.86 mL), and stirred at 353 K for 24 h. The viscose product was washed three times using n-hexane to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, an orange, slightly viscous liquid was obtained.
ACCEPTED MANUSCRIPT 1
RI
PT
H NMR (500 MHz, D2O) δ (ppm) = 9.07 (s, 1 H; NCHN), 7.83 (s, 1 H; CH (ring)), 7.60 (s, 1 H; CH (ring)), 7.15 (dd, J = 8.6 Hz, J = 15.3 Hz, 1 H; NCHCH2), 6.06- 6.11 (m, 1 H; CH2CHCH2), 5.82 (d, J =15.5 Hz, 1 H; CH2CHCH2), 5.47 (d, J = 16.4, Hz, 1 H; CH2CHCH2(cis)), 5.45 (d, J = 17.1 Hz, 2 H; CHCH2(trans)), 4.87 (d, J = 4.7 Hz, 2 H; NCH2CHCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 136.3, 131.5, 129.5, 123.7, 122.0, 120.6, 109.9, 52.4. FT-IR (KBr, ν/cm-1): 3416, 3057, 2856, 1649, 1549, 1423, 1369, 1306, 1168, 950, 758, 622. Anal. Calcd. for C8H11N2Br: C, 44.67; H, 5.15; N, 13.02%. found: C, 44.48; H, 5.09; N, 12.37%. 2.2.3. Synthesis of 1-(2-Azido-3-bromo-propyl)-3-methyl-3H-imidazol-1-ium bromide (2a)
AC CE P
TE
D
MA
NU
SC
To well-stirred slurry of sodium azide (50 mmol, 3.25 g) in 10 mL of dichloromethane at 273 K was added 2.5 mL of 30% HCl, followed by bromine (10 mmol, 0.80 g). After 60 min of further stirring, the organic layer containing the bromine azide was decanted. Then sodium sulfate (1 spatula) was added. The mixture was stirred for additional 30 min and then filtered. 1-allyl-3methylimidazolium bromide (1a) (10 mmol, 1.89 g) in nitromethane (10 mL) was added to round-bottomed flask containing bromine azide solution at 293 K and the mixture was stirred for 24 h. The solvent was removed by a rotary evaporator and the product washed three times using n-hexane and ethyl acetate. After drying the product under vacuum at 333 K for 3 h, a light brown viscous liquid was obtained. 1 H NMR (500 MHz, CDCl3) δ (ppm) = 10.27 (s, 1H; NCHN), 7.42 (s, 1H; CH(ring)), 7.32 (s, 1H; CH(ring)), 5.92-5.97 (m, 1H; CHN3), 5.39 (d, J= 10.15 Hz, 1H; CH2Br(trans)), 5.35 (d, J= 7.05 Hz, 1H; CH2Br(cis)), 4.98 (d, J= 6.2 Hz, 2H; CH2CHN3), 4.09 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 138.2, 131.4, 124.9, 124.0, 120.1, 54.5, 37.6. FT-IR (KBr, ν/cm-1): 3073, 2798, 2107, 1648, 1573, 1460, 1424, 1339, 1164, 949, 840, 757. Anal. Calcd. for C7H11N5Br2: C, 25.87; H, 3.41; N, 21.55%. found: C, 25.60; H, 3.38; N, 21.58%. 2.2.4. Synthesis of 1-(2-Azido-3-bromo-propyl)-3-vinyl-3H-imidazol-1-ium bromide (2b) To well-stirred slurry of sodium azide (50 mmol, 3.25 g) in 10 mL of dichloromethane at 273 K was added 2.5 mL of 30% HCl, followed by bromine (10 mmol, 0.80 g). After 60 min of further stirring, the organic layer containing the bromine azide was decanted. Then sodium sulfate (1 spatula) was added. The mixture was stirred for additional 30 min and then filtered. 1-allyl-3vinylimidazolium bromide (1b) (10 mmol, 2.15 g) in nitromethane (10 mL) was added to roundbottomed flask containing bromine azide solution at 293 K and the mixture was stirred for 24 h. The solvent was removed by a rotary evaporator and the product washed three times using nhexane and ethyl acetate. After drying the product under vacuum at 333 K for 3 h, a light brown viscous liquid was obtained. 1 H NMR (500 MHz, D2O) δ (ppm) = 9.21 (s, 1 H; NCHN), 7.86 (s, 1 H; CH (ring)), 7.63 (s, 1 H; CH (ring)), 7.19 (dd, J = 9.9 Hz, J = 15.1 Hz, 1 H; NCH), 6.01- 6.09 (m, 1 H; CHN3), 5.83 (d, J =15.4 Hz, 1 H; CH2Br(trans)), 5.62 (d, J = 10.6 Hz, 1 H; CH2Br(cis)), 5.46 (d, J = 9.4 Hz, 2 H; CHCH2), 4.91 (d, J = 5.6 Hz, 2 H; NCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 135.1, 130.5, 128.8, 123.6, 122.4, 120.2, 110.2, 52.5. FT-IR (KBr, ν/cm-1): 3426, 3057, 2117, 1652, 1549,
ACCEPTED MANUSCRIPT 1425, 1369, 1308, 1170, 993, 952, 862, 829. Anal. Calcd. for C8H11N5Br2: C, 28.50; H, 3.27; N, 20.78%. found: C, 28.48; H, 3.22; N, 20.85%.
PT
2.2.5. Synthesis of 1-(2-azido-3-methyl-3H-imidazole-1-ium) propyl)-3-vinyl-3H-imidazole-1ium dibromide (3)
AC CE P
TE
D
MA
NU
SC
RI
Path way (A): 1-Vinylimidazole (12 mmol, 1.13 g) was slowly added to the 1-(2-azido-3bromo-propyl)-3-methyl-3H-imidazol-1-ium bromide (2a) (10 mmol, 3.25 g) under solvent free condition. The reaction mixture was stirred for 48 h at 353 K to form 3. After that, the reaction mixture was cooled to room temperature, and then washed three times using ethyl acetate and toluene to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, a dark brown and very viscous liquid was obtained. Path way (B): 1-Methylimidazole (12 mmol, 1.03 g) was slowly added into the 1-(2-azido-3bromo-propyl)-3-vinyl-3H-imidazol-1-ium bromide (2b) (10 mmol, 3.37 g) under solvent free condition. The reaction mixture was stirred for 48 h at 353 K to form 3. After that, the reaction mixture was cooled to room temperature, and then washed three times using ethyl acetate and toluene to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, a dark brown and very viscous liquid was obtained. 1 H NMR (500 MHz, D2O) δ (ppm) = 10.20 (s, 1H; NCHN), 8.58 (s, 1H; NCHN), 7.64 (s, 1H; CH(ring)), 7.48 (s, 1H; CH(ring)), 7.41 (s, 1H; CH(ring)), 7.30 (s, 1H; CH(ring)), 7.23 (dd, J= 4.5 Hz, J= 16.8 Hz, 1H; NCHCH2), 6.00-6.05 (m, 1H, CHN3), 5.44 (dd, J= 5.5 Hz, J= 10.1 Hz, 2H; CHCH2), 5.08 (d, J=1.7 Hz, 2H; NCH2CHN3), 5.01 (d, J= 1.8 Hz, 2H; N3CHCH2N), 4.11 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 136.9, 129.1, 128.7, 124.6, 123.9, 123.1, 122.2, 120.7, 120.2, 58.1, 52.4, 37.2. FT-IR (KBr, ν/cm-1): 3406, 3148, 3099, 2198, 1648, 1575, 1495, 1423, 1342, 1224, 1089, 998, 825, 750. Anal. Calcd. for C12H17N7Br2: C, 34.39; H, 4.09; N, 23.39%. found: C, 34.26; H, 3.97; N, 23.31%. 2.3. General procedure for anion exchange reactions To a solution of IL (10 mmol) in distilled water (20 mL), was added silver dicyanamide (10 mmol, 1.74g) for 1a, 1b, 2a, 2b and (20 mmol, 3.48 gr) for 3. The reaction mixture was stirred for 24 h at 313 K. The green precipitate of silver bromide was formed. After that, the reaction mixture was cooled to room temperature and filtered to remove any precipitated of silver bromide. The water was removed by a rotary evaporator and finally the produced dicyanamide based IL dried under vacuum at 333 K for 3 h. 2.3.1. 1-Allyl-3-methylimidazolium dicyanamide (4a) 1
H NMR (500 MHz, CDCl3) δ (ppm) = 8.63 (s, 1H; NCHN), 7.41 (s, 1H; CH(ring)), 7.36 (s, 1H; CH(ring)), 5.77-6.10 (m, 1H; CH2CHCH2), 5.37 (d, J= 16.8 Hz, 1H; CH2CHCH2(trans)), 5.28 (d, J= 10.8 Hz, 1H; CH2CHCH2(cis)), 4.68 (d, J= 6.3 Hz, 2H; NCH2CHCH2), 3.81(s, 3H; NCH3). 13 C NMR (125 MHz, D2O) δ (ppm) = 136.5, 131.2, 123.7, 122.2, 120.1, 119.1, 51.1, 36.3. FT-IR (KBr, ν/cm-1): 3431, 3144, 3084, 2857, 2233, 2194, 2135, 1573, 1501, 1423, 1312, 1167, 947,
ACCEPTED MANUSCRIPT 761, 622. Anal. Calcd. for C9H11N5: C, 57.13; H, 5.86; N, 37.01%. found: C, 56.98; H, 5.84; N, 36.88%. 2.3.2. 1-Allyl-3-vinylimidazolium dicyanamide (4b) 1
NU
SC
RI
PT
H NMR (500 MHz, D2O) δ (ppm) = 9.05 (s, 1 H; NCHN), 7.78 (s, 1 H; CH (ring)), 7.56 (s, 1 H; CH (ring)), 7.11 (dd, J = 6.7 Hz, J = 15.4 Hz, 1 H; NCHCH2), 6.01- 6.08 (m, 1 H; CH2CHCH2), 5.77 (d, J =15.5 Hz, 1 H; CH2CHCH2(cis)), 5.41 (d, J = 17.7, Hz, 1 H; CH2CHCH2(trans)), 5.39 (d, J = 16.6 Hz, 2 H; CHCH2), 4.84 (d, J = 4.7 Hz, 2 H; NCH2CHCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 135.8, 131.2, 129.4, 124.0, 122.4, 120.6, 118.4, 110.2, 52.7. FT-IR (KBr, ν/cm1 ): 3489, 3087, 2233, 2186, 2127, 1653, 1551, 1423, 1312, 1172, 993, 952, 829, 756, 664. Anal. Calcd. for C10H11N5: C, 59.69; H, 5. 51; N, 34.80%. found: C, 59.25; H, 4.46; N, 34.74%.
TE
D
MA
2.3.3. 1-(2-Azido-3-bromo-propyl)-3-methyl-3H-imidazol-1-ium dicyanamide (5a) 1 H NMR (500 MHz, CDCl3) δ (ppm) = 9.85 (s, 1H; NCHN), 7.40 (s, 1H; CH(ring)), 7.30 (s, 1H; CH(ring)), 6.02-6.09 (m, 1H; CHN3), 5.52 (d, J= 10.9 Hz, 1H; CH2Br(trans)), 5.49 (d, J= 10.4 Hz, 1H; CH2Br(cis)), 4.91 (d, J= 9.5 Hz, 2H; CH2CHN3), 4.05 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 138.9, 130.7, 125.4, 123.6, 122.4, 119.3, 54.5, 37.8. FT-IR (KBr, ν/cm-1): 3431, 3140, 3084, 2658, 2233, 2194, 2135, 2108, 1637, 1572, 1456, 1429, 1332, 1167, 997, 943, 841, 761, 672, 620. Anal. Calcd. for C9H11N8Br: C, 34.74; H, 3.56; N, 36.01%. found: C, 34.59; H, 3.47; N, 36.09%.
AC CE P
2.3.4. 1-(2-Azido-3-bromo-propyl)-3-vinyl-3H-imidazol-1-ium dicyanamide (5b) 1 H NMR (500 MHz, D2O) δ (ppm) = 9.05 (s, 1 H; NCHN), 7.80 (s, 1 H; CH (ring)), 7.57 (s, 1 H; CH (ring)), 7.12 (dd, J = 8.7 Hz, J = 15.5 Hz, 1 H; NCH), 6.01- 6.08 (m, 1 H; CHN3), 5.79 (d, J =15.5 Hz, 1 H; CH2Br(cis)), 5.44 (d, J = 16.9 Hz, 1 H; CH2Br(trans)), 5.41 (d, J = 16.9 Hz, 2 H; CHCH2), 4.85 (d, J = 5.4 Hz, 2 H; NCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 135.0, 130.5, 128.7, 123.5, 122.4, 120.1, 119.8, 110.1, 52.4. FT-IR (KBr, ν/cm-1): 3073, 2235, 2135, 2196, 2117, 1648, 1573, 1460, 1424, 1339, 1312, 1164, 951, 843, 756. Anal. Calcd. for C10H11N8Br: C, 37.16; H, 3.41; N, 34.68%. found: C, 37.18; H, 3.37; N, 34.59%. 2.3.5. 1-(2-Azido-3-methyl-3H-imidazole-1-ium) propyl)-3-vinyl-3H-imidazole-1-ium didicyanamide (6) 1 H NMR (500 MHz, D2O) δ (ppm) = 3.87 (s, 3H; NCH3), 4.61 (d, J= 1.5 Hz, 2H; NCH2CHN3), 4.74 (d, J=1.8 Hz, 2H; NCH2CHN3), 5.01 (dd, J= 5.2 Hz, J= 10.3 Hz, 2H; CHCH2), 5.43-5.53 (m, 1H, CHN3), 6.00 (dd, J= 4.8 Hz, J= 15.9 Hz, 1H; NCHCH2), 7.25 (s, 1H; CH(ring)), 7.39 (s, 1H; CH(ring)), 7.44 (s, 1H; CH(ring)), 7.59 (s, 1H; CH(ring)), 8.64 (s, 1H; NCHN), 9.99 (s, 1H; NCHN). 13C NMR (125 MHz, D2O) δ (ppm) = 136.6, 128.8, 124.3, 123.5, 122.9, 121.9, 121.3, 120.2, 119.5, 118.2, 57.17, 52.2, 36.6. FT-IR (KBr, ν/cm-1): 3414, 3144, 3095, 2292, 2239, 2194, 2134, 1647, 1573, 1511, 1419, 1344, 1228, 1086, 993, 825, 750. Anal. Calcd. for C14H17N10: C, 51.66; H, 5.27; N, 43.07%. found: C, 51.60; H, 5.21; N, 43.09%.
ACCEPTED MANUSCRIPT 3. Results and discussion 3.1. The melting points and densities of the synthesized ILs
AC CE P
TE
D
MA
NU
SC
RI
PT
Melting points (Tm) of the synthesized mono and dicationic ILs are collected in Table 1. Determination of the melting points of compounds 4a and 4b was difficult because they prefer the glass state. From the data in Table 1, it is appear that all of the mono and dicationic ILs containing azide group, are true room temperature liquids. With regard to the cation effect, it can be seen that the melting points of the dicationic ILs are substantially higher than that of the monocationic ILs (Table 1, entries 9, 10). In addition, 3-methyl imidazolium based monocationic ILs containing azide group (Table 1, entries 2, 5, 6) have higher melting points than their corresponding 3-vinyl imidazolium based ILs (Table 1, entries 4, 7, 8). This is a result of high intermolecular attraction due to localized charged density on 3-methyl imidazolium nitrogen. The nature of the anion is one of the main factors was found to affect the melting points of the various mono and dicationic ILs too. It is clear from Table 1, bromide based ILs have higher melting points than their corresponding DCA based ILs. Such result arises from the symmetry of the anions; bromide anion has the most symmetrical sphere, whereas DCA anion has lower symmetry [31].
ACCEPTED MANUSCRIPT
----
1.17
----
188c
1.12
42[20]
Br -
----
1.21
----
N(CN)2-
275c
1.19
29.7
Br -
283
1.29
----
N(CN)2-
271
1.25
51.8
Br -
277
1.36
----
N(CN)2-
263
1.31
30.1
H3C N
N
(1a)
Br -
2
H3C N
N
(4a)
N(CN)2-
3
N
N
(1b)
4
N
N
(4b)
5
H3C N
N
6
H3C N
N
D
N
(2b)
N3
N
N
AC CE P
8
N3
9
H3C N
N
10
H3C N
N
Br
TE
N
SC
(5a) N3
7
NU
Br N3
MA
(2a)
RI
1
N3
Br
(5b)
Br
N
N
(3)
Br -
296
1.56
----
N
N
(6)
N(CN)2-
292
1.49
83.9
N3
a
PT
Table 1. Melting points, densities and viscosities for the synthesized dicationic and monocationic ILs. Compd. Entry Tm(K) ρa(g.cm-3) ηb(cP) Cation Anion
Density measured at 298 K. Viscosity measured at 298 K. c Glass transition. b
Table 1 also shows the data of densities of ILs which were synthesized in this study. Density is one of the major indices to reflect the energy performance of energetic materials, because the higher density usually means the higher mole number of an IL can be packed into a limited volume. Generally, the density of ILs is governed by their molecular structures. It is clear from Table 1 that the densities of the dicationic ILs (Table1, entries 9, 10) are consistently higher than that for the monocationic ILs with the same anions. VVDW/V (VVDW = van der Waals volume, V = molar volume) in the dicationic ILs is larger than in monocationic ILs with the same anions, which implies that the interionic interactions of the dicationic ILs are stronger than that in the monocationic ILs [32]. Comparing the densities of monocationic ILs with the same anion shows two major results: 3-methyl imidazolium based ILs have lower densities than 3-vinyl imidazolium based ILs and ILs containing azide group, have higher densities than other monocationic ILs without any azide groups. Generally, the azide group can increase strong H-
ACCEPTED MANUSCRIPT
PT
bond interactions in the molecules, thereby resulting in higher densities of the ILs containing this functional group. The densities of ILs are also affected by the nature of the organic anion; so that for ILs containing the same cation species, increasing the anion mass leads to increasing the IL density. For this reason, the density of ILs with bromide anion (Table 1, entries 1, 3, 5, 7, 9) is higher than that of the corresponding ILs with DCA anion (Table 1 entries 2, 4, 6, 8, 10).
RI
3.2. The viscosity of dicyanamide based ILs containing azide group
AC CE P
TE
D
MA
NU
SC
Table 1 also summarizes the data of the shear viscosities at 298 K of the dicationic and monocationic ILs containing an azide group with DCA anion. Generally, viscosity is an important property of IL because it strongly influences diffusion of species which are dissolved or dispersed in a media such as IL. Viscosity is ordinarily influenced by the symmetry of the ions. Moreover, the viscosities of ILs are also highly dependent on strong interactive forces such as electrostatic or van der Waals interactions, and hydrogen bonding; greater interactions lead to higher viscosities [33]. In addition, a more planar structure would allow relatively facile slip between molecules [34], resulting in lower viscosity. For imidazolium-based ILs, employing the proper alkyl chains or introducing specified functional groups can decrease the viscosity through reduced van der Waals interactions, while delocalization of the charge on the anion, leads to decrease of the viscosity by weakening hydrogen bonding. It seems that the anion structure of ILs has more obvious effect on the viscosity than the cation. However, it is still unclear why the viscosity is more dependent on the anion structure rather than cation structure. Among the ILs, the use of electron-rich anions such as DCA in combination with imidazolium-based cations can favor the formation of slightly viscous ILs. From Table 1, it can be seen that the dicationic IL with DCA has higher shear viscosity than monocationic ones (Table 1, entry 10). In addition, the shear viscosities of 3-vinyl imidazolium based ILs with DCA, are substantially lower than 3-methyl imidazolium based ones (Table 1, entries 2, 4, 6, 8). The vinyl group can be placed parallel to the imidazole ring and hold the planarity of the cation compared to that when with the saturated methyl substituent. Although the viscosity of 1-(2-azido-3-methyl-3H-imidazole-1-ium) propyl)-3-vinyl-3Himidazole-1-ium di-dicyanamide (compound 6) is higher than its corresponding monocationic analogues, but its viscosity is very lower than other reported dicationic. Generally, the viscosity of imidazolium based dicationic ILs is in the range of 241 to 15540 cP [32, 35-37]. It seems that, asymmetric dicationic structure of compound 6 with an unsaturated vinyl side chain and DCA anion, have created such low viscosity. The effect of temperature on the viscosities of 5a, 5b and 6 were also investigated. Viscosity – temperature dependence for these ILs at several temperatures in the range 298–358 K are shown in Figure 1. As expected, the viscosity of these ILs decreased with increase in temperature. In addition, the viscosity of the dicationic IL is larger than that of the corresponding monocationic ILs.
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
Figure 1. Measured viscosities of 5a, 5b and 6 as a function of temperature.
D
Shear Rate: d(gamma)/dt = 500 1/s.
TE
3.3. Thermal stability of mono and dicationic azide functionalized ILs containing DCA anion
AC CE P
Thermogravimetric analysis (TGA), were conducted to determine the thermal stabilities of new mono and dicationic azide functionalized ILs containing DCA anion. Dynamic runs were carried out at the heating rate 10 K.min-1. The TGA curves recorded for 5a, 5b and 6 were shown in Figure 2 and the decomposition temperatures (Tonset, Tpeak, T50%, Td) for these ILs are summarized in Table 2. As shown in Figure 2, for compound 6, there are two ranges where the mass gently decreases as temperature increases, but there is one range of mass losing for 5a and 5b. For two steps TGA curves, according to the weight percentage of each ion in ILs, it is possible to determine which ion decomposes first. The weight percentage of DCA anion for 6 was calculated and it was 20%. For this dicationic IL, the first decomposition step (502 to 683 K), involves approximately 20% weight loss, can be attributed to the decomposition of DCA anion. Decomposition of the cation occurs from 623 to 843 K. It seems that the anion could modify the beginning of the cation decomposition. At range 843 to 903 K little mass lost is observed. This mass lost is related to inorganic compounds formed in the decomposition processes.
SC
RI
PT
ACCEPTED MANUSCRIPT
MA
NU
Figure 2. TGA curves of the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group obtained at 10 K.min-1.
a
TE
D
Table 2. Dynamic TGA characteristic parameters for the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group. Ionic liquid FW (g.mol-1) Δma (%) Tonset (K) Tpeak (K)b Td (K)c 5a 311.1 ---495.3 558.6 534.1 5b 323.1 ---476.5 545.0 514.2 6 391.4 19.8 513.3 569.2 572.8 Mass loss at the first stage of decomposition. The maximum weight loss at the first range that mass decreases. c The temperature that 10% mass loss.
AC CE P
b
According to the Figure 2, compound 6 starts to decompose at 513.3 K, whereas decomposition of 5a and 5b begins at 495.3 K and 476.5 K respectively. This Figure implies that the thermal stability of dicationic IL is higher than its corresponding monocationic ILs. Furthermore, 3methyl imidazolium based IL (compound 5a) shows much higher thermal stability than 3-vinyl imidazolium based IL (compound 5b). Generally, in ILs with the same anion, thermal stabilities of dicationic ILs are significantly higher than their monocationic analogues, due to their higher charge, higher molecular weight and greater intermolecular interactions [38]. Also, ILs with unsaturated side chains are thermally less stable than the corresponding ILs with saturated side chains [39, 40]. 3.4. Heat capacity of mono and dicationic ionic liquids containing azide group and DCA anion Heat capacity is an important criterion determining the applicability of ILs as heat transfer fluids for heat exchange in chemical plants and solar thermal power generation [41, 42]. The heat capacities of the synthesized mono and dicationic ionic liquids containing azide group and DCA anion were determined in the range from 298 to 398 K for 5a and 5b and from 298 to 343 K for 6 because in these ranges no thermal events take place. The variation of heat capacity with temperature, are shown in Figure 3. The results show that the heat capacity of dicationic IL is higher than that of corresponding monocationic ILs. The value of the heat capacity for the IL increase with an increase in the number of carbon atoms present in the molecule [43]. Also, the
ACCEPTED MANUSCRIPT
MA
NU
SC
RI
PT
heat capacity of 5b is higher than 5a. With the same anion, the high heat capacity of an IL is probably due to an increase in the number of vibrational degrees of freedom in the cation structure.
D
Figure 3. Heat capacities of the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group.
TE
As can be seen in Figure 3, the heat capacity of ILs, increases linearly with temperature. The experimental values were fitted as a function of temperature with the polynomial given as Eq.1: (Eq. 1)
AC CE P
CP = a + bT+ cT2
The polynomial coefficients and the heat capacities at 298 K are reported in Table 3. Table 3. Coefficients of Eq. (1) for the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group. Copmd. T range (K) a (J/g.K) b (J/g.K2) c (J/g.K3) R2 CP,298 (J/g.K) 298 to 398 -5 0.0052 -0.6 0.9841 1.10 5a 298 to 343 -6 0.0058 -0.6 0.9831 1.16 5b 298 to 398 7 -0.7 0.004 0.9209 1.23 6 4. Conclusion Several novel azide functionalized mono and dicationic imidazolium based ILs containing DCA anion were synthesized using 3-methyl imidazole and 3-vinyl imidazole. Characterization of the synthesized ILs, were investigated by NMR, IR spectroscopies and elemental analysis. All of the synthesized mono and dicationic ILs were liquid at room temperature. By comparing the melting point, density, viscosity, thermal stability and heat capacity of the synthesized ILs with each other and with literature data, we found three important results:
ACCEPTED MANUSCRIPT
MA
NU
SC
RI
PT
(I) 3-Vinyl imidazolium based monocationic IL containing azide group and DCA anion, has lower melting point, viscosity, thermal stability and heat capacity than its corresponding 3methyl imidazolium based IL. (II) The thermophysical properties, thermal stability and heat capacity for the synthesized dicationic IL containing azide group and DCA anion (compound 6), was found to be higher than its corresponding monocationic ILs. (III) The viscosity of compound 6 is considerably lower than other dicationic ILs reported in literature. These results confirm that, the existence of unsaturated side chains in the structure of both cation and anion in ILs, caused to decrease the viscosities and melting points of them. Furthermore, ILs with DCA anion, have high thermal stability and heat capacity. Based on the above results, it seems that the new synthesized dicyanamide based azide functionalized dicationic IL, with low viscosity and good thermophysical properties can be used as an acceptable candidate for heat transfer fluids energetic applications as in propellant systems. Acknowledgements
TE
References
D
The authors are grateful to Malek - Ashtar University of Technology for supporting this work.
AC CE P
[1] J.P. Hallett, T. Welton, Room-temperature ionic liquids: solvents for synthesis and catalysis. 2., Chem. Rev. 111 (2011) 3508-3576. [2] F. Jutz, J.M. Andanson, A. Baiker, Ionic liquids and dense carbon dioxide: a beneficial biphasic system for catalysis, Chem. Rev. 111 (2011) 322-353. [3] B. Ni, A.D. Headley, Ionic-liquid-supported (ILs) catalysts for asymmetric organic synthesis, Chem. A. Eur. J. 16 (2010) 4426-4436. [4] Q. Zhang, S. Zhang, Y. Deng, Recent advances in ionic liquid catalysis, Green Chem. 13 (2011) 2619-2637. [5] R. Fareghi-Alamdari, F. Ghorbani Zamani, N. Zekri, An efficient and highly selective ortho tert-butylation of p-cresol with tert-butyl methyl ether catalyzed by sulfonated ionic liquids, J. Serb. Chem. Soc. 79 (2014) 1337-1346. [6] C. Chiappe, M. Malvaldi, C.S. Pomelli, The solvent effect on the diels–alder reaction in ionic liquids: multiparameter linear solvation energy relationships and theoretical analysis, Green Chem. 12 (2010) 1330-1339. [7] N. Isambert, M.M.S. Duque, J.C. Plaquevent, Y. Genisson, J. Rodriguez, T. Constantieux, Multicomponent reactions and ionic liquids: a perfect synergy for eco-compatible heterocyclic synthesis, Chem. Soc. Rev. 40 (2011) 1347-1357. [8] X. Han, D.W. Armstrong, Ionic liquids in separations, Acc. Chem. Res. 40 (2007) 10791086.
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
[9] M.L. Dietz, Ionic liquids as extraction solvents: where do we stand?, Sep. Sci. Technol. 41 (2006) 2047-2063. [10] P. Hapiot, C. Lagrost, Electrochemical reactivity in room-temperature ionic liquids, Chem. Rev. 108 (2008) 2238-2264. [11] D.S. Silvester, Recent advances in the use of ionic liquids for electrochemical sensing, Analyst. 136 (2011) 4871-4882. [12] L. Meli, J. Miao, J.S. Dordick, R.J. Linhardt, Electrospinning from room temperature ionic liquids for biopolymer fiber formation, Green Chem. 12 (2010) 1883-1892. [13] D.A. Walsh, K.R.J. Lovelock, P. Licence, Ultramicroelectrode voltammetry and scanning electrochemical microscopy in room-temperature ionic liquid electrolytes, Chem. Soc. Rev. 39 (2010) 4185-4194. [14] D. Freudenmann, S. Wolf, M. Wolff, C. Feldmann, Ionic liquids: new perspectives for inorganic synthesis, Angew. Chem., Int. Ed. 50 (2011) 11050-11060. [15] Z. Ma, J. Yu, S. Dai, Preparation of inorganic materials using ionic liquids, Adv. Mater. 22 (2010) 261-285. [16] E.R. Parnham, R.E. Morris, Synthesis of zeolites, metal-organic frameworks, and inorganicorganic hybrids, Acc. Chem. Res. 40 (2007) 1005-1013. [17] J. Dupont, J.D. Scholten, On the structural and surface properties of transition-metal nanoparticles in ionic liquids, Chem. Soc. Rev. 39 (2010) 1780-1804. [18] J.F. Wishart, Energy applications of ionic liquids, Energy Environ. Sci. 2 (2009) 956-961. [19] P.S. Kulkarni, C.A.M. Afonso, Deep desulfurization of diesel fuel using ionic liquids: current status and future challenges, Green Chem. 12 (2010) 1139-1149. [20] S. Schneider, T. Hawkins, M. Rosander, G. Vaghjiani, S. Chambreau, G. Drake, Ionic liquids as hypergolic fuels, Energy Fuels. 22 (2008) 2871-2872. [21] S.D. Chambreau, S. Schneider, M. Rosander, T. Hawkins, C.J. Gallegos, M.F. Pastewait, G.L. Vaghjiani, Fourier transform infrared studies in hypergolic ignition of ionic liquids, J. Phys. Chem. A. 112 (2008) 7816-7824. [22] Y.H. Joo, J.M. Shreeve, Nitroimino-tetrazolates and oxy-nitroimino-tetrazolates, J. Am. Chem. Soc. 132 (2010) 15081-15090. [23] R. Wang, H. Xu, Y. Guo, R. Sa, J.M. Shreeve, Bis[3-(5-nitroimino-1,2,4-triazolate)]-based energetic salts: synthesis and promising properties of a new family of high-density insensitive materials, J. Am. Chem. Soc. 132 (2010) 11904-11905. [24] T.M. Klapotke, J. Stierstorfer, The CN7- anion, J. Am. Chem. Soc. 131 (2009) 1122-1134. 5 M. a at , H.Z. Delalu, Methylated azoles, 2-tetrazenes, and hydrazines. Anorg. Allg. Chem. 640 (2014) 1843-1854. [26] (a) S. Bräse, C. Gil, K. Knepper, V. Zimmermann, Organic azides: an exploding diversity of a unique class of compounds, Angew. Chem., Int. Ed. 44 (2005) 5188-5240. (b) M.A. Petrie, J.A. Sheehy, J.A. Boatz, G. Rasul, G.K.S. Prakash, G.A. Olah, K.O. Christe, Novel high-energy density materials. Synthesis and characterization of triazidocarbenium dinitramide, -perchlorate, and –tetrafluoroborate, J. Am. Chem. Soc. 119 (1997) 8802-8808. (c) T.M. Klapötke, B. Krumm,
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
R. Ilg, D. Trögel, R. Tacke, The sila-explosives Si(CH2N3)4 and Si(CH2ONO2)4: silicon analogues of the common explosives pentaerythrityl tetraazide, C(CH2N3)4, and pentaerythritol tetranitrate, C(CH2ONO2)4, J. Am. Chem. Soc. 129 (2007) 6908-6915. (d) K. Banert, Y.H. Joo, T. Rüffer, B. Walfort, H. Lang, The exciting chemistry of tetraazidomethane, Angew. Chem., Int. Ed. 46 (2007) 1168-1171. (e) T. Abe, G.H. Tao, Y.H. Joo, Y. Huang, B. Twamley, J.M. Shreeve, Activation of the C-F bond: transformation of CF3NN- into5-azidotetrazoles, Angew. Chem., Int. Ed. 47 (2008) 7087–7090. (f) Y.H. Joo, J.M. Shreeve, 1, 3-Diazido-2-(azidomethyl)2-propylammonium Salts, Inorg. Chem. 48 (2009) 8431-8438. (g) E.F. Witucki, M.B. Frankel, Synthesis of novel energetic aliphatic compounds, J. Chem. Eng. Data. 24 (1979) 247-249. (h) E.F. Witucki, E.R. Wilson, J.E. Flanagan, M.B. Frankel, Synthesis of novel energetic compounds, J. Chem. Eng. Data. 28 (1983) 285-286. [27] Y.H. Joo, H. Gao, Y. Zhang, J.M. Shreeve, Inorganic or organic azide-containing hypergolic ionic liquids, Inorg. Chem. 49 (2010) 3282–3288. [28] J.D. Clark, Ignition! An informal history of liquid rocket propellants, fourth ed., Rutgers University Press, New Brunswick, N.J, 1972. [29] Y. Zhang, H. Gao, Y.H. Joo, J.M. Shreeve, Ionic liquids as hypergolic fuels, Angew. Chem. Int. Ed. 50 (2011) 9554-9562. [30] D.R. MacFarlane, J. Golding, S. Forsyth, M. Forsyth, G.B. Deacon, Low viscosity ionic liquids based on organic salts of the dicyanamide anion, Chem. Commun. (2001)1430-1431. [31] (a) J.C. Chang, W.Y. Ho, I.W. Sun, Y.L. Tung, M.C. Tsui, T.Y. Wu, S.S. Liang, Synthesis and characterization of dicationic ionic liquids that contain both hydrophilic and hydrophobic anions, Tetrahedron 66 (2010) 6150-6155. (b) K. Matsumoto, R.J. Hagiwara, Structural characteristics of alkylimidazolium-based salts containing fluoroanions, J. Fluorine Chem. 128 (2007) 317-331. [32] H. Shirota, T. Mandai, H. Fukazawa, T. Kato, Comparison between dicationic and monocationic ionic liquids: liquid density, thermal properties, surface tension, and shear viscosity, J. Chem. Eng. Data. 56 (2011) 2453-2459. 33 D. Bejan, N. Ignat’ev, H. Willner, New ionic liquids with the bis[bis(pentafluoroethyl)phosphinyl]imide anion, [(C2F5)2P(O)]2N− synthesis and characterization, J. Fluorine Chem. 131 (2010) 325-332. [34] J. Sun, D.R. MacFarlane, M.A. Forsyth, new family of ionic liquids based on the 1-alkyl-2methyl pyrrolinium cation, Electrochim. Acta. 48 (2003) 1707-1711. [35] T. Payagala, J. Huang, Z.S. Breitbach, P.S. Sharma, D.W. Armstrong, Unsymmetrical dicationic ionic liquids: manipulation of physicochemical properties using specific structural architectures, Chem. Mater. 19 (2007) 5848-5850. [36] A.H. Jadhav, H. Kim, Short oligo (ethylene glycol) functionalized imidazolium dicationic room temperature ionic liquids: synthesis, properties, and catalytic activity in azidation, Chem. Eng. J. 200–202 (2012) 264-274. [37] P. Brown, C.P. Butts, J. Eastoe, E.P. Herna´ndez, F.L. Machadob, R.J. Oliveirac, Dication magnetic ionic liquids with tuneable heteroanions, Chem. Commun. 49 (2013) 2765-2767. [38] J.L. Anderson, R.F. Ding, A. Ellern, D.W. Armstrong, Structure and properties of high stability geminal dicationic ionic liquids, J. Am. Chem. Soc. 127 (2005) 593-604.
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
[39] G.H. Min, T. Yim, H.Y. Lee, D.H. Huh, E.Lee, J. Mun, S.M. Oh, Y.G. Kim, Synthesis and physicochemical properties of ionic liquids: 1-alkenyl-2,3-dimethylimidazolium tetrafluoroborates, Bull. Korean Chem. Soc. 28 (2007) 1562-1566. [40] G.H. Min, T. Yim, H.Y. Lee, D.H. Huh, E. Lee, J. Mun, S.M. Oh, Y.G. Kim, Synthesis and properties of ionic liquids: imidazolium tetrafluoroborates with unsaturated side chains, Bull. Korean Chem. Soc. 27 (2006) 847-852. [41] J.D. Holbrey, Heat capacities of common ionic liquids. Potential applications as thermal fluids, Chim. Oggi. 25 (2007) 24-26. [42] J.M.P. Franca, C.A. Nieto de Castro, M.M. Lopes, V.M.B. Nunes, Influence of thermophysical properties of ionic liquids in chemical process design, J. Chem. Eng. Data. 54 (2009) 2569-2575. [43] Y.U. Paulechka, Heat capacity of room-temperature ionic liquids: a critical review, J. Phys. Chem. Ref. Data. 39 (2010) 033108.1- 033108.23.
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
Graphical abstract
ACCEPTED MANUSCRIPT Highlights
TE
D
MA
NU
SC
RI
PT
Several new azide functionalized ionic liquids were synthesized. The viscosity of unsymmetrical dicationic IL with dicyanamide is 83.9 cP at 298 K. The viscosities of monocationic ILs with dicyanamide are less than 51.8 cP at 298 K. Thermal behavior of mono and dicationic ILs with dicyanamide were investigated. Dicationic IL with dicyanamide has good thermal stability and heat capacity.
AC CE P
S0167-7322(15)31022-9 doi:10.1016/j.molliq.2016.11.006 MOLLIQ 6547
To appear in:
Journal of Molecular Liquids
Received date: Revised date: Accepted date:
9 November 2015 11 August 2016 2 November 2016
Please cite this article as: Reza Fareghi-Alamdari, Razieh Hatefipour, Low viscosity azide-containing mono and dicationic ionic liquids with unsaturated side chain, Journal of Molecular Liquids (2016), doi:10.1016/j.molliq.2016.11.006
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Low Viscosity Azide-Containing Mono and Dicationic Ionic Liquids with Unsaturated Side Chain
PT
Reza Fareghi - Alamdaria, Razieh Hatefipoura a Faculty of Chemistry and Chemical Engineering, Malek - Ashtar University of Technology, Tehran, Iran.
RI
Abstract
TE
D
MA
NU
SC
A new class of azide-functionalized monocationic and unsymmetrical dicationic ionic liquids (ILs) with low viscosity and high liquid range was synthesized. All of the synthesized ILs, were characterized by FT-IR, 1HNMR, 13CNMR spectroscopies and elemental analysis. Some thermophysical properties including melting point, density, shear viscosity, decomposition temperature and heat capacity of the unsymmetrical dicationic azide functionalized IL with dicyanamide (DCA) were measured. To find the unique and general features of this dicationic IL, its properties were compared with the ones of the similar monocationic ILs. The results showed that the shear viscosity, density, thermal stability and heat capacity of the unsymmetrical dicationic IL are higher than monocationic analogues. In addition we found that the shear viscosity for the synthesized unsymmetrical dicationic IL containing azide group and DCA anion is 83.9 cP whereas the shear viscosities for other dicationic ILs reported in the literature are higher than 240 cP.
AC CE P
Keywords: Ionic liquid; Azide group; Dicyanamide; Shear viscosity; Thermogravimetric analysis. 1. Introduction
In recent years, ionic liquids (ILs) have attracted much attention owing to their unique physicochemical properties. Their properties can be varied to some extent for specific applications by changing the anions, cations or alkyl substituents of the cations. The notable characteristics of ILs are their non-measurable vapor pressure, high thermal stability, wide liquid range and solvating properties for diverse kinds of materials. Because of these particular properties, ILs have brought a green revolution in chemistry and chemical engineering in the past dozen years. Researches and developments that involve ILs are prevalent in nearly every branch of chemistry and material science, including catalysis [1- 4], organic synthesis [5- 7], separation and analysis [8, 9], electrochemistry [10- 13], material chemistry [14- 17], and energy technology [18, 19]. Moreover certain ILs do behave as fuels and energetic materials [20, 21]. In development of new high-performance energetic materials, nitrogen-rich ILs represent an individual class of energetic molecular frameworks, which have recently attracted significant interest in the design of energetic materials due to their high heats of formation, density, and thermal stability. These energetic ionic liquids (EILs) are most often composed of high nitrogen
Corresponding authors: Fax: +98-21-44658251; Tel: +98-937-3381632. E-mail: [email protected]
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
organic cations (e.g., tetrazolium [22], triazolium [23], guanidinium [24], and imizadolium [25]) and bulky anions with one or more energetic groups such as −NO2, −N3 and –CN. Recently some reports about the development and preparation of energy-rich compounds which contain organic azide groups have appeared [24, 26]. Each azide group adds approximately 280 KJ.mol-1 to the energy content of molecule [27]. Among ILs, azide containing ILs are thermally stable and have significantly reduced sensitivity and toxicity characteristics because having negligible vapor pressure [27]. The most importance of the EILs, is their application as liquid fuel in bipropellant systems. In these systems, spontaneous reaction occurs when the fuel and oxidizer are contacted together. It is desirable for these reactions to proceed as rapidly as possible [28]. The fuel of a bipropellant must be a compound with a wide liquid range and low melting point. Additionally, for propellant applications, fuels with low viscosities are highly desirable because the low viscosity can facilitate rapid mixing of IL as fuel with the oxidizer and therefore encourage rapid initiation processes [29]. In the cases of imidazolium based ILs, it has been shown that employing the proper alkyl chains or introducing specified functional groups can decrease the viscosity. Also it seems that the anion structure of EILs has an obvious effect on the viscosity. The combination of the dicyanamide (DCA) anion with imidazolium-based cations, can favor the formation of slightly viscous EILs [20]. Nowadays, the search for new ILs with low viscosities has also been a hot topic in the fields of EILs. We report here, several new series of mono and dicationic imidazolium based ILs containing an azide group. Since DCA anion is expected to decrease melting point and viscosity and increase thermal stability of ILs [30], this anion was chosen to design the structure of desired ILs. All of the synthesized ILs were liquid at room temperature. Density, melting point and some thermophysical properties including shear viscosity, heat capacity and decomposition temperature of the synthesized ILs containing azide functionality with DCA, were studied.
2. Experimental
2.1. Materials and instruments
All of the solvents and chemicals were purchased from Sigma-Aldrich chemical company and were used without further purification. 1H and 13CNMR spectra were recorded on a Brucker Avance DRX – 500 MHz spectrometer, in CDCl3 or D2O. TMS was used as an internal standard. FT-IR spectra were recorded on a Nicolet 800 instrument. Elemental analyses were conducted using Heraeous CHN analyzer (Germany) instrument. Water content was eliminated in a treatment before the measurements of densities and viscosities that consisted of isothermal heating at 378 K for 0.5 h. This was found to be the optimal condition for removing all water presented in the ILs matrix. To prevent water absorption, all ILs were stored in a desiccator and handed inside a glovebox under an inert atmosphere of dry nitrogen. The water content of the ILs was determined by means of Mettler DL-18 Karl-Fischer titration, and the water content in synthesized ILs ranged from 0.002 to 0.006 w/w. The melting point of synthesized ILs and the heat capacity of the unsymmetrical dicationic IL were measured using a differential scanning calorimeter (DSC) in a Perkin Elmer instrument (Pyris 6 DSC model) in a nitrogen atmosphere
ACCEPTED MANUSCRIPT
MA
NU
SC
RI
PT
with a temperature rate of 20 K.min-1. The measurements were carried out using (9±1) mg of sample. The melting transition (T=429.31 K, 3.296 kg.mol-1) of the standard indium sample was used in order to calibrate temperature and energy. The zero-heat flow producer described by TA instruments was flowed for heat capacity measurements using a synthetic sapphire sample as the reference compound. All these experiments allowed estimating an overall uncertainty of ±0.1 K in temperature and ±3% in the heat capacities. Density was measured at room temperature using a Micromeritics Accupyc 1330 gas pycnometer, whereas viscosities, η, were analyzed using Anton Paar MCR 300 rheometer with a cp 25-2 fixture (25 mm diameter, 2° cone angle). Viscosity measurements were carried out at atmospheric pressure and temperature range of 298 to 373 K. The estimated uncertainty of measured densities is ±5×10-3 g.cm-3. The relative uncertainty in the dynamic viscosity was ±1.1%, whereas the uncertainty in temperature was within ±0.1 K. Thermogravimetric analysis (TGA) was conducted using a thermal analysis instrument Perkin Elmer (Pyris Diamond model) in a nitrogen atmosphere. In this method, the temperature range was between 298 and 1273 K at a heating rate of 10 K.min-1. Runs were carried out in 40 μL alumina pans and under an inert atmosphere of nitrogen. Nitrogen flow was 20 mL.min-1. Initial mass introduced in to the pan was set to (10±1) mg. 2.2. Synthesis and characterization of mono and dicationic ILs
AC CE P
TE
D
The synthesis routes for the preparation of imidazolium based ILs are shown in scheme 1. In this research some monocationic ILs (1a, 2a, 4a, 5a, 1b, 2b, 4b, and 5b) and two novel unsymmetrical dicationic azide functionalized ILs (3, 6) were synthesized. Molecular structures of all of the synthesized ILs were characterized via FT-IR, 1HNMR, 13CNMR spectroscopies and elemental analysis. All the data of characterizations are in accordance with the expected compositions and structures.
ACCEPTED MANUSCRIPT R1 N
N +
Br
Solvent free
R1=
1a: methyl 1b: R1= vinyl
Br
Br
R1=
2a: methyl 2b: R1= vinyl
N3 N
Solvent free 80 °C, 48h
AgN(CN)2
AgN(CN)2
H2O, 40 °C, 24h
H2O, 40 °C, 24h
R1 N
N
Br N(CN)2
R1=
5a: methyl 5b: R1= vinyl
TE
4a: R1= methyl 4b: R1= vinyl
D
N(CN)2
N
N R2
3: R1, R2 = methyl, vinyl
AgN(CN)2 H2O, 40 °C, 24h
N3
R1 N
N 2Br
NU
Br
R1 N
N
RI
CH3NO2, 20°C
R1 N
N R2
SC
N
N
MA
R1 N
N3
BrN3
PT
80 °C, 24h
N3 R1 N
N
N
N R2
2N(CN)2 6: R1, R2 = methyl, vinyl
AC CE P
Scheme 1. Synthesis routes of mono and diatonic ionic liquids. 2.2.1. Synthesis of 1-allyl-3-methylimidazolium bromide (1a) 1-Methylimidazole (10 mmol, 0.82 g) was mixed with allyl bromide (10 mmol, 0.86 mL), and stirred at 353 K for 24 h. The viscose product was washed three times using n-hexane to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, a brown, slightly viscous liquid was obtained. 1 H NMR (500 MHz, CDCl3) δ (ppm) = 10.33 (s, 1H; NCHN), 7.55 (s, 1H; CH(ring)), 7.39 (s, 1H; CH(ring)), 5.78-6.05 (m, 1H; CH2CHCH2), 5.45 (d, J= 17.0 Hz, 1H; CH2CHCH2(trans)), 5.42 (d, J= 10.1 Hz, 1H; CH2CHCH2(cis)), 4.97 (d, J= 6.4 Hz, 2H; NCH2CHCH2), 4.08 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 136.4, 130.2, 123.8, 122.1, 122.0, 51.6, 36.7. FTIR (KBr, ν/cm-1): 3084, 2857, 1625, 1573, 1448, 1312, 1167, 948, 843, 761, 760. Anal. Calcd. for C7H11N2Br: C, 41.40; H, 5.46; N, 13.79%. found: C, 41.38; H, 5.41; N, 13.68%. 2.2.2. Synthesis of 1-allyl-3-vinylimidazolium bromide (1b) 1-Vinylimidazole (10 mmol, 0.94 g) was mixed with allyl bromide (10 mmol, 0.86 mL), and stirred at 353 K for 24 h. The viscose product was washed three times using n-hexane to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, an orange, slightly viscous liquid was obtained.
ACCEPTED MANUSCRIPT 1
RI
PT
H NMR (500 MHz, D2O) δ (ppm) = 9.07 (s, 1 H; NCHN), 7.83 (s, 1 H; CH (ring)), 7.60 (s, 1 H; CH (ring)), 7.15 (dd, J = 8.6 Hz, J = 15.3 Hz, 1 H; NCHCH2), 6.06- 6.11 (m, 1 H; CH2CHCH2), 5.82 (d, J =15.5 Hz, 1 H; CH2CHCH2), 5.47 (d, J = 16.4, Hz, 1 H; CH2CHCH2(cis)), 5.45 (d, J = 17.1 Hz, 2 H; CHCH2(trans)), 4.87 (d, J = 4.7 Hz, 2 H; NCH2CHCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 136.3, 131.5, 129.5, 123.7, 122.0, 120.6, 109.9, 52.4. FT-IR (KBr, ν/cm-1): 3416, 3057, 2856, 1649, 1549, 1423, 1369, 1306, 1168, 950, 758, 622. Anal. Calcd. for C8H11N2Br: C, 44.67; H, 5.15; N, 13.02%. found: C, 44.48; H, 5.09; N, 12.37%. 2.2.3. Synthesis of 1-(2-Azido-3-bromo-propyl)-3-methyl-3H-imidazol-1-ium bromide (2a)
AC CE P
TE
D
MA
NU
SC
To well-stirred slurry of sodium azide (50 mmol, 3.25 g) in 10 mL of dichloromethane at 273 K was added 2.5 mL of 30% HCl, followed by bromine (10 mmol, 0.80 g). After 60 min of further stirring, the organic layer containing the bromine azide was decanted. Then sodium sulfate (1 spatula) was added. The mixture was stirred for additional 30 min and then filtered. 1-allyl-3methylimidazolium bromide (1a) (10 mmol, 1.89 g) in nitromethane (10 mL) was added to round-bottomed flask containing bromine azide solution at 293 K and the mixture was stirred for 24 h. The solvent was removed by a rotary evaporator and the product washed three times using n-hexane and ethyl acetate. After drying the product under vacuum at 333 K for 3 h, a light brown viscous liquid was obtained. 1 H NMR (500 MHz, CDCl3) δ (ppm) = 10.27 (s, 1H; NCHN), 7.42 (s, 1H; CH(ring)), 7.32 (s, 1H; CH(ring)), 5.92-5.97 (m, 1H; CHN3), 5.39 (d, J= 10.15 Hz, 1H; CH2Br(trans)), 5.35 (d, J= 7.05 Hz, 1H; CH2Br(cis)), 4.98 (d, J= 6.2 Hz, 2H; CH2CHN3), 4.09 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 138.2, 131.4, 124.9, 124.0, 120.1, 54.5, 37.6. FT-IR (KBr, ν/cm-1): 3073, 2798, 2107, 1648, 1573, 1460, 1424, 1339, 1164, 949, 840, 757. Anal. Calcd. for C7H11N5Br2: C, 25.87; H, 3.41; N, 21.55%. found: C, 25.60; H, 3.38; N, 21.58%. 2.2.4. Synthesis of 1-(2-Azido-3-bromo-propyl)-3-vinyl-3H-imidazol-1-ium bromide (2b) To well-stirred slurry of sodium azide (50 mmol, 3.25 g) in 10 mL of dichloromethane at 273 K was added 2.5 mL of 30% HCl, followed by bromine (10 mmol, 0.80 g). After 60 min of further stirring, the organic layer containing the bromine azide was decanted. Then sodium sulfate (1 spatula) was added. The mixture was stirred for additional 30 min and then filtered. 1-allyl-3vinylimidazolium bromide (1b) (10 mmol, 2.15 g) in nitromethane (10 mL) was added to roundbottomed flask containing bromine azide solution at 293 K and the mixture was stirred for 24 h. The solvent was removed by a rotary evaporator and the product washed three times using nhexane and ethyl acetate. After drying the product under vacuum at 333 K for 3 h, a light brown viscous liquid was obtained. 1 H NMR (500 MHz, D2O) δ (ppm) = 9.21 (s, 1 H; NCHN), 7.86 (s, 1 H; CH (ring)), 7.63 (s, 1 H; CH (ring)), 7.19 (dd, J = 9.9 Hz, J = 15.1 Hz, 1 H; NCH), 6.01- 6.09 (m, 1 H; CHN3), 5.83 (d, J =15.4 Hz, 1 H; CH2Br(trans)), 5.62 (d, J = 10.6 Hz, 1 H; CH2Br(cis)), 5.46 (d, J = 9.4 Hz, 2 H; CHCH2), 4.91 (d, J = 5.6 Hz, 2 H; NCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 135.1, 130.5, 128.8, 123.6, 122.4, 120.2, 110.2, 52.5. FT-IR (KBr, ν/cm-1): 3426, 3057, 2117, 1652, 1549,
ACCEPTED MANUSCRIPT 1425, 1369, 1308, 1170, 993, 952, 862, 829. Anal. Calcd. for C8H11N5Br2: C, 28.50; H, 3.27; N, 20.78%. found: C, 28.48; H, 3.22; N, 20.85%.
PT
2.2.5. Synthesis of 1-(2-azido-3-methyl-3H-imidazole-1-ium) propyl)-3-vinyl-3H-imidazole-1ium dibromide (3)
AC CE P
TE
D
MA
NU
SC
RI
Path way (A): 1-Vinylimidazole (12 mmol, 1.13 g) was slowly added to the 1-(2-azido-3bromo-propyl)-3-methyl-3H-imidazol-1-ium bromide (2a) (10 mmol, 3.25 g) under solvent free condition. The reaction mixture was stirred for 48 h at 353 K to form 3. After that, the reaction mixture was cooled to room temperature, and then washed three times using ethyl acetate and toluene to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, a dark brown and very viscous liquid was obtained. Path way (B): 1-Methylimidazole (12 mmol, 1.03 g) was slowly added into the 1-(2-azido-3bromo-propyl)-3-vinyl-3H-imidazol-1-ium bromide (2b) (10 mmol, 3.37 g) under solvent free condition. The reaction mixture was stirred for 48 h at 353 K to form 3. After that, the reaction mixture was cooled to room temperature, and then washed three times using ethyl acetate and toluene to remove any unreacted reactants. After drying the product under vacuum at 333 K for 3 h, a dark brown and very viscous liquid was obtained. 1 H NMR (500 MHz, D2O) δ (ppm) = 10.20 (s, 1H; NCHN), 8.58 (s, 1H; NCHN), 7.64 (s, 1H; CH(ring)), 7.48 (s, 1H; CH(ring)), 7.41 (s, 1H; CH(ring)), 7.30 (s, 1H; CH(ring)), 7.23 (dd, J= 4.5 Hz, J= 16.8 Hz, 1H; NCHCH2), 6.00-6.05 (m, 1H, CHN3), 5.44 (dd, J= 5.5 Hz, J= 10.1 Hz, 2H; CHCH2), 5.08 (d, J=1.7 Hz, 2H; NCH2CHN3), 5.01 (d, J= 1.8 Hz, 2H; N3CHCH2N), 4.11 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 136.9, 129.1, 128.7, 124.6, 123.9, 123.1, 122.2, 120.7, 120.2, 58.1, 52.4, 37.2. FT-IR (KBr, ν/cm-1): 3406, 3148, 3099, 2198, 1648, 1575, 1495, 1423, 1342, 1224, 1089, 998, 825, 750. Anal. Calcd. for C12H17N7Br2: C, 34.39; H, 4.09; N, 23.39%. found: C, 34.26; H, 3.97; N, 23.31%. 2.3. General procedure for anion exchange reactions To a solution of IL (10 mmol) in distilled water (20 mL), was added silver dicyanamide (10 mmol, 1.74g) for 1a, 1b, 2a, 2b and (20 mmol, 3.48 gr) for 3. The reaction mixture was stirred for 24 h at 313 K. The green precipitate of silver bromide was formed. After that, the reaction mixture was cooled to room temperature and filtered to remove any precipitated of silver bromide. The water was removed by a rotary evaporator and finally the produced dicyanamide based IL dried under vacuum at 333 K for 3 h. 2.3.1. 1-Allyl-3-methylimidazolium dicyanamide (4a) 1
H NMR (500 MHz, CDCl3) δ (ppm) = 8.63 (s, 1H; NCHN), 7.41 (s, 1H; CH(ring)), 7.36 (s, 1H; CH(ring)), 5.77-6.10 (m, 1H; CH2CHCH2), 5.37 (d, J= 16.8 Hz, 1H; CH2CHCH2(trans)), 5.28 (d, J= 10.8 Hz, 1H; CH2CHCH2(cis)), 4.68 (d, J= 6.3 Hz, 2H; NCH2CHCH2), 3.81(s, 3H; NCH3). 13 C NMR (125 MHz, D2O) δ (ppm) = 136.5, 131.2, 123.7, 122.2, 120.1, 119.1, 51.1, 36.3. FT-IR (KBr, ν/cm-1): 3431, 3144, 3084, 2857, 2233, 2194, 2135, 1573, 1501, 1423, 1312, 1167, 947,
ACCEPTED MANUSCRIPT 761, 622. Anal. Calcd. for C9H11N5: C, 57.13; H, 5.86; N, 37.01%. found: C, 56.98; H, 5.84; N, 36.88%. 2.3.2. 1-Allyl-3-vinylimidazolium dicyanamide (4b) 1
NU
SC
RI
PT
H NMR (500 MHz, D2O) δ (ppm) = 9.05 (s, 1 H; NCHN), 7.78 (s, 1 H; CH (ring)), 7.56 (s, 1 H; CH (ring)), 7.11 (dd, J = 6.7 Hz, J = 15.4 Hz, 1 H; NCHCH2), 6.01- 6.08 (m, 1 H; CH2CHCH2), 5.77 (d, J =15.5 Hz, 1 H; CH2CHCH2(cis)), 5.41 (d, J = 17.7, Hz, 1 H; CH2CHCH2(trans)), 5.39 (d, J = 16.6 Hz, 2 H; CHCH2), 4.84 (d, J = 4.7 Hz, 2 H; NCH2CHCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 135.8, 131.2, 129.4, 124.0, 122.4, 120.6, 118.4, 110.2, 52.7. FT-IR (KBr, ν/cm1 ): 3489, 3087, 2233, 2186, 2127, 1653, 1551, 1423, 1312, 1172, 993, 952, 829, 756, 664. Anal. Calcd. for C10H11N5: C, 59.69; H, 5. 51; N, 34.80%. found: C, 59.25; H, 4.46; N, 34.74%.
TE
D
MA
2.3.3. 1-(2-Azido-3-bromo-propyl)-3-methyl-3H-imidazol-1-ium dicyanamide (5a) 1 H NMR (500 MHz, CDCl3) δ (ppm) = 9.85 (s, 1H; NCHN), 7.40 (s, 1H; CH(ring)), 7.30 (s, 1H; CH(ring)), 6.02-6.09 (m, 1H; CHN3), 5.52 (d, J= 10.9 Hz, 1H; CH2Br(trans)), 5.49 (d, J= 10.4 Hz, 1H; CH2Br(cis)), 4.91 (d, J= 9.5 Hz, 2H; CH2CHN3), 4.05 (s, 3H; NCH3). 13C NMR (125 MHz, D2O) δ (ppm) = 138.9, 130.7, 125.4, 123.6, 122.4, 119.3, 54.5, 37.8. FT-IR (KBr, ν/cm-1): 3431, 3140, 3084, 2658, 2233, 2194, 2135, 2108, 1637, 1572, 1456, 1429, 1332, 1167, 997, 943, 841, 761, 672, 620. Anal. Calcd. for C9H11N8Br: C, 34.74; H, 3.56; N, 36.01%. found: C, 34.59; H, 3.47; N, 36.09%.
AC CE P
2.3.4. 1-(2-Azido-3-bromo-propyl)-3-vinyl-3H-imidazol-1-ium dicyanamide (5b) 1 H NMR (500 MHz, D2O) δ (ppm) = 9.05 (s, 1 H; NCHN), 7.80 (s, 1 H; CH (ring)), 7.57 (s, 1 H; CH (ring)), 7.12 (dd, J = 8.7 Hz, J = 15.5 Hz, 1 H; NCH), 6.01- 6.08 (m, 1 H; CHN3), 5.79 (d, J =15.5 Hz, 1 H; CH2Br(cis)), 5.44 (d, J = 16.9 Hz, 1 H; CH2Br(trans)), 5.41 (d, J = 16.9 Hz, 2 H; CHCH2), 4.85 (d, J = 5.4 Hz, 2 H; NCH2). 13C NMR (125 MHz, D2O) δ (ppm) = 135.0, 130.5, 128.7, 123.5, 122.4, 120.1, 119.8, 110.1, 52.4. FT-IR (KBr, ν/cm-1): 3073, 2235, 2135, 2196, 2117, 1648, 1573, 1460, 1424, 1339, 1312, 1164, 951, 843, 756. Anal. Calcd. for C10H11N8Br: C, 37.16; H, 3.41; N, 34.68%. found: C, 37.18; H, 3.37; N, 34.59%. 2.3.5. 1-(2-Azido-3-methyl-3H-imidazole-1-ium) propyl)-3-vinyl-3H-imidazole-1-ium didicyanamide (6) 1 H NMR (500 MHz, D2O) δ (ppm) = 3.87 (s, 3H; NCH3), 4.61 (d, J= 1.5 Hz, 2H; NCH2CHN3), 4.74 (d, J=1.8 Hz, 2H; NCH2CHN3), 5.01 (dd, J= 5.2 Hz, J= 10.3 Hz, 2H; CHCH2), 5.43-5.53 (m, 1H, CHN3), 6.00 (dd, J= 4.8 Hz, J= 15.9 Hz, 1H; NCHCH2), 7.25 (s, 1H; CH(ring)), 7.39 (s, 1H; CH(ring)), 7.44 (s, 1H; CH(ring)), 7.59 (s, 1H; CH(ring)), 8.64 (s, 1H; NCHN), 9.99 (s, 1H; NCHN). 13C NMR (125 MHz, D2O) δ (ppm) = 136.6, 128.8, 124.3, 123.5, 122.9, 121.9, 121.3, 120.2, 119.5, 118.2, 57.17, 52.2, 36.6. FT-IR (KBr, ν/cm-1): 3414, 3144, 3095, 2292, 2239, 2194, 2134, 1647, 1573, 1511, 1419, 1344, 1228, 1086, 993, 825, 750. Anal. Calcd. for C14H17N10: C, 51.66; H, 5.27; N, 43.07%. found: C, 51.60; H, 5.21; N, 43.09%.
ACCEPTED MANUSCRIPT 3. Results and discussion 3.1. The melting points and densities of the synthesized ILs
AC CE P
TE
D
MA
NU
SC
RI
PT
Melting points (Tm) of the synthesized mono and dicationic ILs are collected in Table 1. Determination of the melting points of compounds 4a and 4b was difficult because they prefer the glass state. From the data in Table 1, it is appear that all of the mono and dicationic ILs containing azide group, are true room temperature liquids. With regard to the cation effect, it can be seen that the melting points of the dicationic ILs are substantially higher than that of the monocationic ILs (Table 1, entries 9, 10). In addition, 3-methyl imidazolium based monocationic ILs containing azide group (Table 1, entries 2, 5, 6) have higher melting points than their corresponding 3-vinyl imidazolium based ILs (Table 1, entries 4, 7, 8). This is a result of high intermolecular attraction due to localized charged density on 3-methyl imidazolium nitrogen. The nature of the anion is one of the main factors was found to affect the melting points of the various mono and dicationic ILs too. It is clear from Table 1, bromide based ILs have higher melting points than their corresponding DCA based ILs. Such result arises from the symmetry of the anions; bromide anion has the most symmetrical sphere, whereas DCA anion has lower symmetry [31].
ACCEPTED MANUSCRIPT
----
1.17
----
188c
1.12
42[20]
Br -
----
1.21
----
N(CN)2-
275c
1.19
29.7
Br -
283
1.29
----
N(CN)2-
271
1.25
51.8
Br -
277
1.36
----
N(CN)2-
263
1.31
30.1
H3C N
N
(1a)
Br -
2
H3C N
N
(4a)
N(CN)2-
3
N
N
(1b)
4
N
N
(4b)
5
H3C N
N
6
H3C N
N
D
N
(2b)
N3
N
N
AC CE P
8
N3
9
H3C N
N
10
H3C N
N
Br
TE
N
SC
(5a) N3
7
NU
Br N3
MA
(2a)
RI
1
N3
Br
(5b)
Br
N
N
(3)
Br -
296
1.56
----
N
N
(6)
N(CN)2-
292
1.49
83.9
N3
a
PT
Table 1. Melting points, densities and viscosities for the synthesized dicationic and monocationic ILs. Compd. Entry Tm(K) ρa(g.cm-3) ηb(cP) Cation Anion
Density measured at 298 K. Viscosity measured at 298 K. c Glass transition. b
Table 1 also shows the data of densities of ILs which were synthesized in this study. Density is one of the major indices to reflect the energy performance of energetic materials, because the higher density usually means the higher mole number of an IL can be packed into a limited volume. Generally, the density of ILs is governed by their molecular structures. It is clear from Table 1 that the densities of the dicationic ILs (Table1, entries 9, 10) are consistently higher than that for the monocationic ILs with the same anions. VVDW/V (VVDW = van der Waals volume, V = molar volume) in the dicationic ILs is larger than in monocationic ILs with the same anions, which implies that the interionic interactions of the dicationic ILs are stronger than that in the monocationic ILs [32]. Comparing the densities of monocationic ILs with the same anion shows two major results: 3-methyl imidazolium based ILs have lower densities than 3-vinyl imidazolium based ILs and ILs containing azide group, have higher densities than other monocationic ILs without any azide groups. Generally, the azide group can increase strong H-
ACCEPTED MANUSCRIPT
PT
bond interactions in the molecules, thereby resulting in higher densities of the ILs containing this functional group. The densities of ILs are also affected by the nature of the organic anion; so that for ILs containing the same cation species, increasing the anion mass leads to increasing the IL density. For this reason, the density of ILs with bromide anion (Table 1, entries 1, 3, 5, 7, 9) is higher than that of the corresponding ILs with DCA anion (Table 1 entries 2, 4, 6, 8, 10).
RI
3.2. The viscosity of dicyanamide based ILs containing azide group
AC CE P
TE
D
MA
NU
SC
Table 1 also summarizes the data of the shear viscosities at 298 K of the dicationic and monocationic ILs containing an azide group with DCA anion. Generally, viscosity is an important property of IL because it strongly influences diffusion of species which are dissolved or dispersed in a media such as IL. Viscosity is ordinarily influenced by the symmetry of the ions. Moreover, the viscosities of ILs are also highly dependent on strong interactive forces such as electrostatic or van der Waals interactions, and hydrogen bonding; greater interactions lead to higher viscosities [33]. In addition, a more planar structure would allow relatively facile slip between molecules [34], resulting in lower viscosity. For imidazolium-based ILs, employing the proper alkyl chains or introducing specified functional groups can decrease the viscosity through reduced van der Waals interactions, while delocalization of the charge on the anion, leads to decrease of the viscosity by weakening hydrogen bonding. It seems that the anion structure of ILs has more obvious effect on the viscosity than the cation. However, it is still unclear why the viscosity is more dependent on the anion structure rather than cation structure. Among the ILs, the use of electron-rich anions such as DCA in combination with imidazolium-based cations can favor the formation of slightly viscous ILs. From Table 1, it can be seen that the dicationic IL with DCA has higher shear viscosity than monocationic ones (Table 1, entry 10). In addition, the shear viscosities of 3-vinyl imidazolium based ILs with DCA, are substantially lower than 3-methyl imidazolium based ones (Table 1, entries 2, 4, 6, 8). The vinyl group can be placed parallel to the imidazole ring and hold the planarity of the cation compared to that when with the saturated methyl substituent. Although the viscosity of 1-(2-azido-3-methyl-3H-imidazole-1-ium) propyl)-3-vinyl-3Himidazole-1-ium di-dicyanamide (compound 6) is higher than its corresponding monocationic analogues, but its viscosity is very lower than other reported dicationic. Generally, the viscosity of imidazolium based dicationic ILs is in the range of 241 to 15540 cP [32, 35-37]. It seems that, asymmetric dicationic structure of compound 6 with an unsaturated vinyl side chain and DCA anion, have created such low viscosity. The effect of temperature on the viscosities of 5a, 5b and 6 were also investigated. Viscosity – temperature dependence for these ILs at several temperatures in the range 298–358 K are shown in Figure 1. As expected, the viscosity of these ILs decreased with increase in temperature. In addition, the viscosity of the dicationic IL is larger than that of the corresponding monocationic ILs.
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
Figure 1. Measured viscosities of 5a, 5b and 6 as a function of temperature.
D
Shear Rate: d(gamma)/dt = 500 1/s.
TE
3.3. Thermal stability of mono and dicationic azide functionalized ILs containing DCA anion
AC CE P
Thermogravimetric analysis (TGA), were conducted to determine the thermal stabilities of new mono and dicationic azide functionalized ILs containing DCA anion. Dynamic runs were carried out at the heating rate 10 K.min-1. The TGA curves recorded for 5a, 5b and 6 were shown in Figure 2 and the decomposition temperatures (Tonset, Tpeak, T50%, Td) for these ILs are summarized in Table 2. As shown in Figure 2, for compound 6, there are two ranges where the mass gently decreases as temperature increases, but there is one range of mass losing for 5a and 5b. For two steps TGA curves, according to the weight percentage of each ion in ILs, it is possible to determine which ion decomposes first. The weight percentage of DCA anion for 6 was calculated and it was 20%. For this dicationic IL, the first decomposition step (502 to 683 K), involves approximately 20% weight loss, can be attributed to the decomposition of DCA anion. Decomposition of the cation occurs from 623 to 843 K. It seems that the anion could modify the beginning of the cation decomposition. At range 843 to 903 K little mass lost is observed. This mass lost is related to inorganic compounds formed in the decomposition processes.
SC
RI
PT
ACCEPTED MANUSCRIPT
MA
NU
Figure 2. TGA curves of the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group obtained at 10 K.min-1.
a
TE
D
Table 2. Dynamic TGA characteristic parameters for the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group. Ionic liquid FW (g.mol-1) Δma (%) Tonset (K) Tpeak (K)b Td (K)c 5a 311.1 ---495.3 558.6 534.1 5b 323.1 ---476.5 545.0 514.2 6 391.4 19.8 513.3 569.2 572.8 Mass loss at the first stage of decomposition. The maximum weight loss at the first range that mass decreases. c The temperature that 10% mass loss.
AC CE P
b
According to the Figure 2, compound 6 starts to decompose at 513.3 K, whereas decomposition of 5a and 5b begins at 495.3 K and 476.5 K respectively. This Figure implies that the thermal stability of dicationic IL is higher than its corresponding monocationic ILs. Furthermore, 3methyl imidazolium based IL (compound 5a) shows much higher thermal stability than 3-vinyl imidazolium based IL (compound 5b). Generally, in ILs with the same anion, thermal stabilities of dicationic ILs are significantly higher than their monocationic analogues, due to their higher charge, higher molecular weight and greater intermolecular interactions [38]. Also, ILs with unsaturated side chains are thermally less stable than the corresponding ILs with saturated side chains [39, 40]. 3.4. Heat capacity of mono and dicationic ionic liquids containing azide group and DCA anion Heat capacity is an important criterion determining the applicability of ILs as heat transfer fluids for heat exchange in chemical plants and solar thermal power generation [41, 42]. The heat capacities of the synthesized mono and dicationic ionic liquids containing azide group and DCA anion were determined in the range from 298 to 398 K for 5a and 5b and from 298 to 343 K for 6 because in these ranges no thermal events take place. The variation of heat capacity with temperature, are shown in Figure 3. The results show that the heat capacity of dicationic IL is higher than that of corresponding monocationic ILs. The value of the heat capacity for the IL increase with an increase in the number of carbon atoms present in the molecule [43]. Also, the
ACCEPTED MANUSCRIPT
MA
NU
SC
RI
PT
heat capacity of 5b is higher than 5a. With the same anion, the high heat capacity of an IL is probably due to an increase in the number of vibrational degrees of freedom in the cation structure.
D
Figure 3. Heat capacities of the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group.
TE
As can be seen in Figure 3, the heat capacity of ILs, increases linearly with temperature. The experimental values were fitted as a function of temperature with the polynomial given as Eq.1: (Eq. 1)
AC CE P
CP = a + bT+ cT2
The polynomial coefficients and the heat capacities at 298 K are reported in Table 3. Table 3. Coefficients of Eq. (1) for the synthesized mono and dicationic dicyanamide based ionic liquids containing azide group. Copmd. T range (K) a (J/g.K) b (J/g.K2) c (J/g.K3) R2 CP,298 (J/g.K) 298 to 398 -5 0.0052 -0.6 0.9841 1.10 5a 298 to 343 -6 0.0058 -0.6 0.9831 1.16 5b 298 to 398 7 -0.7 0.004 0.9209 1.23 6 4. Conclusion Several novel azide functionalized mono and dicationic imidazolium based ILs containing DCA anion were synthesized using 3-methyl imidazole and 3-vinyl imidazole. Characterization of the synthesized ILs, were investigated by NMR, IR spectroscopies and elemental analysis. All of the synthesized mono and dicationic ILs were liquid at room temperature. By comparing the melting point, density, viscosity, thermal stability and heat capacity of the synthesized ILs with each other and with literature data, we found three important results:
ACCEPTED MANUSCRIPT
MA
NU
SC
RI
PT
(I) 3-Vinyl imidazolium based monocationic IL containing azide group and DCA anion, has lower melting point, viscosity, thermal stability and heat capacity than its corresponding 3methyl imidazolium based IL. (II) The thermophysical properties, thermal stability and heat capacity for the synthesized dicationic IL containing azide group and DCA anion (compound 6), was found to be higher than its corresponding monocationic ILs. (III) The viscosity of compound 6 is considerably lower than other dicationic ILs reported in literature. These results confirm that, the existence of unsaturated side chains in the structure of both cation and anion in ILs, caused to decrease the viscosities and melting points of them. Furthermore, ILs with DCA anion, have high thermal stability and heat capacity. Based on the above results, it seems that the new synthesized dicyanamide based azide functionalized dicationic IL, with low viscosity and good thermophysical properties can be used as an acceptable candidate for heat transfer fluids energetic applications as in propellant systems. Acknowledgements
TE
References
D
The authors are grateful to Malek - Ashtar University of Technology for supporting this work.
AC CE P
[1] J.P. Hallett, T. Welton, Room-temperature ionic liquids: solvents for synthesis and catalysis. 2., Chem. Rev. 111 (2011) 3508-3576. [2] F. Jutz, J.M. Andanson, A. Baiker, Ionic liquids and dense carbon dioxide: a beneficial biphasic system for catalysis, Chem. Rev. 111 (2011) 322-353. [3] B. Ni, A.D. Headley, Ionic-liquid-supported (ILs) catalysts for asymmetric organic synthesis, Chem. A. Eur. J. 16 (2010) 4426-4436. [4] Q. Zhang, S. Zhang, Y. Deng, Recent advances in ionic liquid catalysis, Green Chem. 13 (2011) 2619-2637. [5] R. Fareghi-Alamdari, F. Ghorbani Zamani, N. Zekri, An efficient and highly selective ortho tert-butylation of p-cresol with tert-butyl methyl ether catalyzed by sulfonated ionic liquids, J. Serb. Chem. Soc. 79 (2014) 1337-1346. [6] C. Chiappe, M. Malvaldi, C.S. Pomelli, The solvent effect on the diels–alder reaction in ionic liquids: multiparameter linear solvation energy relationships and theoretical analysis, Green Chem. 12 (2010) 1330-1339. [7] N. Isambert, M.M.S. Duque, J.C. Plaquevent, Y. Genisson, J. Rodriguez, T. Constantieux, Multicomponent reactions and ionic liquids: a perfect synergy for eco-compatible heterocyclic synthesis, Chem. Soc. Rev. 40 (2011) 1347-1357. [8] X. Han, D.W. Armstrong, Ionic liquids in separations, Acc. Chem. Res. 40 (2007) 10791086.
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
[9] M.L. Dietz, Ionic liquids as extraction solvents: where do we stand?, Sep. Sci. Technol. 41 (2006) 2047-2063. [10] P. Hapiot, C. Lagrost, Electrochemical reactivity in room-temperature ionic liquids, Chem. Rev. 108 (2008) 2238-2264. [11] D.S. Silvester, Recent advances in the use of ionic liquids for electrochemical sensing, Analyst. 136 (2011) 4871-4882. [12] L. Meli, J. Miao, J.S. Dordick, R.J. Linhardt, Electrospinning from room temperature ionic liquids for biopolymer fiber formation, Green Chem. 12 (2010) 1883-1892. [13] D.A. Walsh, K.R.J. Lovelock, P. Licence, Ultramicroelectrode voltammetry and scanning electrochemical microscopy in room-temperature ionic liquid electrolytes, Chem. Soc. Rev. 39 (2010) 4185-4194. [14] D. Freudenmann, S. Wolf, M. Wolff, C. Feldmann, Ionic liquids: new perspectives for inorganic synthesis, Angew. Chem., Int. Ed. 50 (2011) 11050-11060. [15] Z. Ma, J. Yu, S. Dai, Preparation of inorganic materials using ionic liquids, Adv. Mater. 22 (2010) 261-285. [16] E.R. Parnham, R.E. Morris, Synthesis of zeolites, metal-organic frameworks, and inorganicorganic hybrids, Acc. Chem. Res. 40 (2007) 1005-1013. [17] J. Dupont, J.D. Scholten, On the structural and surface properties of transition-metal nanoparticles in ionic liquids, Chem. Soc. Rev. 39 (2010) 1780-1804. [18] J.F. Wishart, Energy applications of ionic liquids, Energy Environ. Sci. 2 (2009) 956-961. [19] P.S. Kulkarni, C.A.M. Afonso, Deep desulfurization of diesel fuel using ionic liquids: current status and future challenges, Green Chem. 12 (2010) 1139-1149. [20] S. Schneider, T. Hawkins, M. Rosander, G. Vaghjiani, S. Chambreau, G. Drake, Ionic liquids as hypergolic fuels, Energy Fuels. 22 (2008) 2871-2872. [21] S.D. Chambreau, S. Schneider, M. Rosander, T. Hawkins, C.J. Gallegos, M.F. Pastewait, G.L. Vaghjiani, Fourier transform infrared studies in hypergolic ignition of ionic liquids, J. Phys. Chem. A. 112 (2008) 7816-7824. [22] Y.H. Joo, J.M. Shreeve, Nitroimino-tetrazolates and oxy-nitroimino-tetrazolates, J. Am. Chem. Soc. 132 (2010) 15081-15090. [23] R. Wang, H. Xu, Y. Guo, R. Sa, J.M. Shreeve, Bis[3-(5-nitroimino-1,2,4-triazolate)]-based energetic salts: synthesis and promising properties of a new family of high-density insensitive materials, J. Am. Chem. Soc. 132 (2010) 11904-11905. [24] T.M. Klapotke, J. Stierstorfer, The CN7- anion, J. Am. Chem. Soc. 131 (2009) 1122-1134. 5 M. a at , H.Z. Delalu, Methylated azoles, 2-tetrazenes, and hydrazines. Anorg. Allg. Chem. 640 (2014) 1843-1854. [26] (a) S. Bräse, C. Gil, K. Knepper, V. Zimmermann, Organic azides: an exploding diversity of a unique class of compounds, Angew. Chem., Int. Ed. 44 (2005) 5188-5240. (b) M.A. Petrie, J.A. Sheehy, J.A. Boatz, G. Rasul, G.K.S. Prakash, G.A. Olah, K.O. Christe, Novel high-energy density materials. Synthesis and characterization of triazidocarbenium dinitramide, -perchlorate, and –tetrafluoroborate, J. Am. Chem. Soc. 119 (1997) 8802-8808. (c) T.M. Klapötke, B. Krumm,
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
R. Ilg, D. Trögel, R. Tacke, The sila-explosives Si(CH2N3)4 and Si(CH2ONO2)4: silicon analogues of the common explosives pentaerythrityl tetraazide, C(CH2N3)4, and pentaerythritol tetranitrate, C(CH2ONO2)4, J. Am. Chem. Soc. 129 (2007) 6908-6915. (d) K. Banert, Y.H. Joo, T. Rüffer, B. Walfort, H. Lang, The exciting chemistry of tetraazidomethane, Angew. Chem., Int. Ed. 46 (2007) 1168-1171. (e) T. Abe, G.H. Tao, Y.H. Joo, Y. Huang, B. Twamley, J.M. Shreeve, Activation of the C-F bond: transformation of CF3NN- into5-azidotetrazoles, Angew. Chem., Int. Ed. 47 (2008) 7087–7090. (f) Y.H. Joo, J.M. Shreeve, 1, 3-Diazido-2-(azidomethyl)2-propylammonium Salts, Inorg. Chem. 48 (2009) 8431-8438. (g) E.F. Witucki, M.B. Frankel, Synthesis of novel energetic aliphatic compounds, J. Chem. Eng. Data. 24 (1979) 247-249. (h) E.F. Witucki, E.R. Wilson, J.E. Flanagan, M.B. Frankel, Synthesis of novel energetic compounds, J. Chem. Eng. Data. 28 (1983) 285-286. [27] Y.H. Joo, H. Gao, Y. Zhang, J.M. Shreeve, Inorganic or organic azide-containing hypergolic ionic liquids, Inorg. Chem. 49 (2010) 3282–3288. [28] J.D. Clark, Ignition! An informal history of liquid rocket propellants, fourth ed., Rutgers University Press, New Brunswick, N.J, 1972. [29] Y. Zhang, H. Gao, Y.H. Joo, J.M. Shreeve, Ionic liquids as hypergolic fuels, Angew. Chem. Int. Ed. 50 (2011) 9554-9562. [30] D.R. MacFarlane, J. Golding, S. Forsyth, M. Forsyth, G.B. Deacon, Low viscosity ionic liquids based on organic salts of the dicyanamide anion, Chem. Commun. (2001)1430-1431. [31] (a) J.C. Chang, W.Y. Ho, I.W. Sun, Y.L. Tung, M.C. Tsui, T.Y. Wu, S.S. Liang, Synthesis and characterization of dicationic ionic liquids that contain both hydrophilic and hydrophobic anions, Tetrahedron 66 (2010) 6150-6155. (b) K. Matsumoto, R.J. Hagiwara, Structural characteristics of alkylimidazolium-based salts containing fluoroanions, J. Fluorine Chem. 128 (2007) 317-331. [32] H. Shirota, T. Mandai, H. Fukazawa, T. Kato, Comparison between dicationic and monocationic ionic liquids: liquid density, thermal properties, surface tension, and shear viscosity, J. Chem. Eng. Data. 56 (2011) 2453-2459. 33 D. Bejan, N. Ignat’ev, H. Willner, New ionic liquids with the bis[bis(pentafluoroethyl)phosphinyl]imide anion, [(C2F5)2P(O)]2N− synthesis and characterization, J. Fluorine Chem. 131 (2010) 325-332. [34] J. Sun, D.R. MacFarlane, M.A. Forsyth, new family of ionic liquids based on the 1-alkyl-2methyl pyrrolinium cation, Electrochim. Acta. 48 (2003) 1707-1711. [35] T. Payagala, J. Huang, Z.S. Breitbach, P.S. Sharma, D.W. Armstrong, Unsymmetrical dicationic ionic liquids: manipulation of physicochemical properties using specific structural architectures, Chem. Mater. 19 (2007) 5848-5850. [36] A.H. Jadhav, H. Kim, Short oligo (ethylene glycol) functionalized imidazolium dicationic room temperature ionic liquids: synthesis, properties, and catalytic activity in azidation, Chem. Eng. J. 200–202 (2012) 264-274. [37] P. Brown, C.P. Butts, J. Eastoe, E.P. Herna´ndez, F.L. Machadob, R.J. Oliveirac, Dication magnetic ionic liquids with tuneable heteroanions, Chem. Commun. 49 (2013) 2765-2767. [38] J.L. Anderson, R.F. Ding, A. Ellern, D.W. Armstrong, Structure and properties of high stability geminal dicationic ionic liquids, J. Am. Chem. Soc. 127 (2005) 593-604.
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
[39] G.H. Min, T. Yim, H.Y. Lee, D.H. Huh, E.Lee, J. Mun, S.M. Oh, Y.G. Kim, Synthesis and physicochemical properties of ionic liquids: 1-alkenyl-2,3-dimethylimidazolium tetrafluoroborates, Bull. Korean Chem. Soc. 28 (2007) 1562-1566. [40] G.H. Min, T. Yim, H.Y. Lee, D.H. Huh, E. Lee, J. Mun, S.M. Oh, Y.G. Kim, Synthesis and properties of ionic liquids: imidazolium tetrafluoroborates with unsaturated side chains, Bull. Korean Chem. Soc. 27 (2006) 847-852. [41] J.D. Holbrey, Heat capacities of common ionic liquids. Potential applications as thermal fluids, Chim. Oggi. 25 (2007) 24-26. [42] J.M.P. Franca, C.A. Nieto de Castro, M.M. Lopes, V.M.B. Nunes, Influence of thermophysical properties of ionic liquids in chemical process design, J. Chem. Eng. Data. 54 (2009) 2569-2575. [43] Y.U. Paulechka, Heat capacity of room-temperature ionic liquids: a critical review, J. Phys. Chem. Ref. Data. 39 (2010) 033108.1- 033108.23.
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
Graphical abstract
ACCEPTED MANUSCRIPT Highlights
TE
D
MA
NU
SC
RI
PT
Several new azide functionalized ionic liquids were synthesized. The viscosity of unsymmetrical dicationic IL with dicyanamide is 83.9 cP at 298 K. The viscosities of monocationic ILs with dicyanamide are less than 51.8 cP at 298 K. Thermal behavior of mono and dicationic ILs with dicyanamide were investigated. Dicationic IL with dicyanamide has good thermal stability and heat capacity.
AC CE P