Synthesis, structure and properties of imidazolium-based energetic ionic liquids

Yang, Hengquan; Liu, Yuejia; Ning, Hongli; Lei, Jianlei; Hu, Gang

doi:10.1039/c7ra05601j

Cited by 13 publications

(14 citation statements)

References 46 publications

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“…To unravel the links between the idealistic situation of an ion pair or a small cluster and the real crystalline material at room temperature, the DFT calculations were compared with experimental data from the solid. For this purpose, the geometries of the ion pair and its dimer were deduced from Single Crystal X‐ray diffraction (SCXRD) measurements reported on the Cambridge Crystallographic Data Centre (CCDC, entry number 1550837) . Table compares selected geometric parameters obtained by the DFT simulations and the SCXRD experiments.…”

Section: Resultsmentioning

confidence: 99%

“…Ionic liquids (ILs) are fascinating ionic materials that have attracted considerable attention in various fields in recent years. This includes organic synthesis and catalysis, electrochemistry, chemical sensing,, and dye‐sensitized solar cells, but also their potential use as energetic materials,, lubricants, and electro‐wetting agents, has sparked an interest in academia and industry. Their attractive and potentially tunable properties make them not just replacements for conventional solvents but open up opportunities to use them as new platforms for advanced multi‐purpose materials, for example by combining them with nanostructured materials …”

Section: Introductionmentioning

confidence: 99%

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Clusters of the Ionic Liquid 1‐Hydroxyethyl‐3‐methylimidazolium Picrate: From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State

2018

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Interonic interactions determine the macroscopic properties of ionic liquids (ILs). Hence, unravelling the relationships between the microscopic and macroscopic scales is key for rational design. Combining density functional theory (DFT) calculations of isolated ion pairs and vibrational spectroscopy of the condensed phase (fluid or solid) has become a very common approach. In the present work, we make a step towards understanding how the physicochemical effects in small gas phase clusters of a hydroxyl functionalized imidazolium-picrate IL relate with the molecular structure and interactions of the corresponding solid material taking 1-hydroxyethyl-3-methylimidazolium picrate, C OHmimPic, as an example. In the isolated ion pair, strong alkyl-OH⋅⋅⋅Pic hydrogen bonding interactions are found rather than the commonly observed hydrogen bonding interactions at the slightly acidic C(2)-H site of the imidazolium ring. However, this part of the cation plays an important role when clusters of ion pairs in the gas phase and inside a crystal lattice are considered. For example, in the dimeric ion-pair cluster, one centre (O*) with two interaction sites (C(2)-H-O* and alkyl OH-Pic) is observed. This configuration is suggested by single crystal X-ray diffraction (XRD), vibrational spectroscopy, and the dispersion-corrected DFT calculations. Hence, the study provides evidence for the appearance of theoretical gas phase clusters in an actual solidified ionic liquid. This ion pair dimer formation may be a general behavior of hydroxyl functionalized imidazolium ILs, but further research is needed to draw a final conclusion. Moreover, the Raman spectra confirm the exclusive gauche conformation of the hyroxyl functionalized alkyl chain.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Clusters of the Ionic Liquid 1‐Hydroxyethyl‐3‐methylimidazolium Picrate: From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State

2018

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“…Comparatively, the introduction of the nitrooxy group in side chains or the methyl group on C‐2 has an opposite effect on the energetic properties of 2 and 4 a‐f . The detonation velocities and detonation pressures of energetic salts 2 and 4 a‐f with an 1,2‐dimethyl‐3‐(2‐nitrooxyethyl)imidazolium cation are much higher than those of energetic salts with an 1,2‐dimethyl‐3‐(2‐hydroxyethyl)imidazolium cation, but slightly lower than those of energetic salts with an 1‐methyl‐3‐(2‐nitrooxyethyl)imidazolium cation, when their anions are the same. This shows that the introduction of nitrooxy energetic group into the cation can improve their energetic properties.…”

Section: Resultsmentioning

confidence: 88%

“…The decomposition temperatures of the salts are given in Table . Comparatively, the decomposition temperatures of 2 and 4 a‐f with an 1,2‐dimethyl‐3‐(2‐nitrooxyethyl)imidazolium cation are generally lower than those of energetic salts with an 1,2‐dimethyl‐3‐(2‐hydroxyethyl)imidazolium cation, but higher than those of energetic salts with an 1‐methyl‐3‐(2‐nitrooxyethyl)imidazolium cation, when their anions are the same. This shows that the introduction of the nitrooxy group in side chains or the methyl group on C‐2 has an opposite effect on their thermo‐stabilities.…”

Section: Resultsmentioning

confidence: 91%

Energetic N‐nitrooxyethylimidazolium Salts: Synthesis, Structures and Properties

Yang

Liu

et al. 2019

ChemistrySelect

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Energetic salts 2 and 4 a-f, comprising an energetic 1,2-dimethyl-3-(2-nitrooxyethyl)imidazolium cation and energetic anions such as nitrate, 3,5-dinitro-1,2,4-triazolate, picrate, 3-nitro-5oxo-1,2,4-triazolate, dinitromethanide, dinitramide and 5-nitrotetrazolate, were easily synthesized via quaternization, nitration and metathesis. The salts were fully characterized by Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR) or elemental analysis. The structure of picrate 4 b was also studied via single crystal X-ray diffraction. The thermal properties of 2 and 4 a-f were investigated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). DSC data show that 3, 5-dinitro-1, 2, 4-triazolate 4 a, dinitromethanide 4 d, dinitramide 4 e and 5-nitrotetrazolate 4 f are typical ionic liquids with a glass transition temperature of À 58°C to À 22°C and a melting point below 100°C. TGA indicates that 2, 4 a-c and 4 f have a good thermal stability and a decomposition temperature above 155°C. Besides, the energetic properties of salts 2 and 4 a-f were calculated. The detonation velocities of the salts are 6.62-7.42 km/s, approaching those of TNT.[a] Dr.

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“…Solid-state crystal structure analysis is very useful in determining the dependence on intermolecular forces and predicting volumetric heat expansion. Yet, studies have shown that the inherent intermolecular organization of imidazolium-based ILs alter the crystal state by forming either triclinic (for RTILs containing oxygen and/or high attractive forces) or monoclinic (weak attractive interactions) [ 35 ]. Furthermore, identifying key features of crystal structures can be very useful in predicting heat expansion trends.…”

Section: Results and Analysismentioning

confidence: 99%

Role of Heat Expansion with a Series of Ionic Liquids: The Case for Isochoric Thermoelectric Generators and Minimal Steric Repulsion

Jackson

Engel

Vuong

2019

Entropy

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The role of convection in liquid thermoelectric cells may be difficult to predict because the inter- and intramolecular interactions are not currently incorporated into thermodynamic models. Here, we study the thermoelectric response of a series of five anhydrous 1-methyl-3- alkylimidazolium halide ionic liquids with varied chain length and counterion in a high-aspect-ratio, horizontal-temperature-gradient geometry, where convection is minimal. While a canonical constant-volume thermodynamic model predicts that the longer aliphatic groups exhibit larger Seebeck coefficients, we instead measure the opposite: Longer aliphatic chains correlate with lower densities and greater heat expansion, stronger intermolecular associations, stronger steric repulsion, and lower Seebeck coefficients. As evidence of the critical role of thermal expansion, we measure that the Seebeck effect is nonlinear: Values of −2.8 mV/K with a 10 K temperature difference and −1.8 mV/K with a 50 K difference are measured with ether ion. Our results indicate that steric repulsion and heat expansion are important considerations in ionic liquid design; with large temperature differences, the Seebeck coefficient correlates negatively with heat expansion. Our results suggest that Seebeck values will improve if thermal expansion is limited in a pressurized, isochoric, convection-free design.

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Synthesis, structure and properties of imidazolium-based energetic ionic liquids

Abstract: Energetic ionic liquids bearing a wide liquid temperature range were easily synthesized, which display good thermal stabilities and energetic properties.

Cited by 13 publications

References 46 publications

Clusters of the Ionic Liquid 1‐Hydroxyethyl‐3‐methylimidazolium Picrate: From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State

Clusters of the Ionic Liquid 1‐Hydroxyethyl‐3‐methylimidazolium Picrate: From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State

Energetic N‐nitrooxyethylimidazolium Salts: Synthesis, Structures and Properties

Role of Heat Expansion with a Series of Ionic Liquids: The Case for Isochoric Thermoelectric Generators and Minimal Steric Repulsion

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