Yanqiang Zhang

Dual Amino‐Functionalised Phosphonium Ionic Liquids for CO2 Capture

A series of 20 dual amino-functionalised phosphonium ionic liquids, (3-aminopropyl)tributylphosphonium amino acid salts ([aP(4443)][AA], in which [AA](-) = [Ala](-), [Arg](-), [Asn](-), [Asp](-), [Cys](-), [Gln](-), [Glu](-), [Gly](-), [His](-), [Ile](-), [Leu](-), [Lys](-), [Met](-), [Phe](-), [Pro](-), [Ser](-), [Thr](-), [Trp](-), [Tyr](-) and [Val](-)), has been prepared. Their physicochemical properties, such as density, viscosity, glass transition and thermal decomposition temperatures and conductivity, have been determined. In particular, the [aP(4443)][AA] ionic liquids (ILs) have low glass transition temperatures ranging from -69.7 to -29.6 degrees C and high decomposition temperatures (all above 200 degrees C). The effects of the variation of the structure of [AA](-) on the above physicochemical properties are discussed. Furthermore, the CO(2) absorption of [aP(4443)][Gly], [aP(4443)][Ala], [aP(4443)][Val] and [aP(4443)][Leu], taken as examples, was investigated. It was found that the supported absorption of CO(2) by the [aP(4443)][AA] ILs almost reaches equilibrium within 80 min, the chemical absorption of CO(2) by the [aP(4443)][AA] ILs approaches 1 mol CO(2) per mol ionic liquid (twice that reported before) and the [aP(4443)][AA] ILs can be repeatedly recycled for CO(2) uptake.

3,4,5-Trinitropyrazole-Based Energetic Salts

High-density energetic salts that are comprised of nitrogen-rich cations and the 3,4,5-trinitropyrazolate anion were synthesized in high yield by neutralization or metathesis reactions. The resulting salts were fully characterized by (1)H, (13)C NMR, and IR spectroscopy; differential scanning calorimetry; and elemental analysis. Additionally, the structures of the 3,5-diaminotriazolium and triaminoguanidinium 3,4,5-trinitropyrazolates were confirmed by single-crystal X-ray diffraction. Based on the measured densities and calculated heats of formation, the detonation performances (pressure: 23.74-31.89 GPa; velocity: 7586-8543 ms(-1); Cheetah 5.0) of the 3,4,5-trinitropyrazolate salts are comparable with 1,3,5-triamino-2,4,6-trinitrobenzene (TATB; 31.15 GPa and 8114 ms(-1)). Impact sensitivities were determined to be no less than 35 J by hammer tests, which places these salts in the insensitive class.

Ionic liquids as hypergolic fuels.

In propellant systems, fuels of choice continue to be hydrazine and its derivatives, even though they comprise a class of acutely carcinogenic and toxic substances which exhibit rather high vapor pressures and require expensive handling procedures and costly safety precautions. Only recently (2008), ionic liquids (salts with melting points less than 100 °C) with the dicyanamide anion were shown to exhibit hypergolic properties (instantaneous ignition when contacted with oxidizers (100 % nitric acid, WFNA)). Such liquids tend to have low volatilities, and high thermal and chemical stabilities, and often exhibit long liquid ranges which could allow utilization of these substances as bipropellant fuels over a variety of conditions. A new family of dicyanoborates is presented, which can be synthesized in water, with substituted N-acyclic, N-cyclic, and azolium cations has met nearly all of the desired important criteria needed for well-performing fuels.

Derivatives of 5-nitro-1,2,3-2H-triazole – high performance energetic materials

The energetic derivatives of 5-nitro-1,2,3-2H-triazole, which include 2-(methyl or amino)-4-(nitramino, azido, or nitro)-5-nitro-1,2,3-2H-triazoles, were prepared in moderate yields, and confirmed with NMR and IR spectroscopy, and elemental analysis. Their key properties, viz., melting and decomposition temperatures, densities, detonation pressures and velocities, and impact sensitivities, were measured or calculated. Among the new derivatives, 2-amino-4,5-dinitro-1,2,3-2H-triazole exhibits properties (Tm, 94 °C; Td, 190 °C; ρ, 1.83 g cm−3; P, 36.2 Gpa, vD, 8843 m s−1, IS, 24 J), comparable with RDX (Tm, 205 °C; Td, 230 °C; ρ, 1.80 g cm−3; P, 35.0 Gpa, vD, 8762 m s−1, IS, 7.5 J), and may have potential as a high-performance energetic material.

Inorganic or organic azide-containing hypergolic ionic liquids.

Recently extensive research has focused on replacing toxic hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine as liquid propellant fuels. 2-Azido-N,N-dimethylethylamine (1) is a good candidate to replace hydrazine derivatives in certain hypergolic fuel applications. Energetic ionic liquids that contain the 2-azido-N,N,N-trimethylethylammonium cation with nitrocyanamide, dicyanamide, dinitramide, or azide anion have been successfully synthesized in good yields by metathesis reactions. Ionic liquids have received considerable attention as energetic materials. The replacement of hydrazine with tertiary ammonium salts is especially attractive since many ionic liquids are models for green chemistry. In this work, new azide-functionalized ionic liquids are demonstrated to exhibit hypergolic activity with such oxidizers as 100% nitric acid or nitrogen tetraoxide (NTO).

4-Amino-3,5-dinitropyrazolate salts—highly insensitive energetic materials†

Energetic salts based on the 4-amino-3,5-dinitropyrazolate anion and selected nitrogen-rich cations were prepared in high yield by neutralization or metathesis reactions. Their key properties of the resulting energetic salts, such as melting point, thermal stability (169–303 °C), density (1.54–1.84 g cm−3), impact sensitivity (>60 J), heat of formation, and detonation pressure (20.99–32.55 GPa) and velocity (7712–8751 m s−1), were measured or calculated. As highly insensitive energetic materials, salts 9 (32.55 GPa, 8743 m s−1) and 11 (28.85 GPa, 8751 m s−1) are comparable with 1,3,5-triamino-2,4,6-trinitrobenzene (TATB, 31.15 GPa and 8114 m s−1).

Synthesis and properties of 3,4,5-trinitropyrazole-1-ol and its energetic salts

3,4,5-Trinitropyrazole-1-ol and its nitrogen-rich salts were synthesized and well characterized by 1H, 13C NMR (some with 15N NMR), and IR spectroscopy, and by elemental analysis. Additionally, the structures of the ammonium and triazolium 3,4,5-trinitropyrazole-olates were confirmed by single-crystal X-ray diffraction. With respect to measured or calculated properties, such as thermal stability (Td, 118–186 °C), density (1.72–1.90 g cm−3), detonation performance (P, 28.77–36.40 GPa; vD, 8175–8676 m s−1), and impact sensitivity (1–40 J), 3,4,5-trinitropyrazole-1-ol and its salts have the potential to be useful energetic materials.

Hypergolic N,N-Dimethylhydrazinium Ionic Liquids

N,N-Dimethylhydrazinium dicyanamide and nitrocyanamide ionic liquids (ILs) were prepared by quaterization of N,N-dimethylhydrazine with alkyl halides followed by metathesis reactions with silver dicyanamide or silver nitrocyanamide. The key physicochemical properties, such as melting point and decomposition temperatures, density, viscosity, heat of formation, detonation pressure and velocity, and specific impulse were measured/calculated. The impact of anions and alkyl-substituted cations on these properties is demonstrated. Droplet tests with white-fuming nitric acid (WFNA) as an oxidizer were utilized to show that the 14 new N,N-dimethylhydrazinium salts are hypergolic with ignition delay (ID) times ranging from 22 to 1642 ms, thereby suggesting that some may have potential as bipropellants.

Nitrogen‐Rich Salts Based on Energetic Nitroaminodiazido[1,3,5]triazine and Guanazine

Highly dense nitrogen-rich ionic compounds are potential high-performance energetic materials for use in military and industrial venues. Guanazinium salts with promising energetic anions and a family of energetic salts based on nitrogen-rich cations and the 6-nitroamino-2,4-diazido[1,3,5]triazine anion (NADAT) were prepared and fully characterized by elemental analysis, IR spectroscopy, (1)H NMR and (13)C NMR spectroscopy, and differential scanning calorimetry (DSC). The crystal structures of neutral NADAT (2) and its biguanidinium salt 5 were determined by single-crystal X-ray diffraction (2: orthorhombic, Pnma; 5: monoclinic, P2(1)). Additionally, the isomerization behavior of 2 in solution was investigated by proton-decoupled (13)C and (15)N NMR spectroscopy. All the new salts exhibit desirable physical properties, such as relatively high densities (1.63-1.78 g cm(-3)) and moderate thermal stabilities (T(d) = 130-196 °C for 3-10 and 209-257 °C for 11-15). Theoretical performance calculations (Gaussian 03 and Cheetah 5.0) gave detonation pressures and velocities for the ionic compounds 3-15 in the range of 21.0-30.3 GPa and 7675-9048 m s(-1), respectively, which makes them competitive energetic materials.

4‐Nitramino‐3,5‐dinitropyrazole‐Based Energetic Salts

4-Nitramino-3,5-dinitropyrazole was prepared and stabilized through the formation of its ammonium salt. With selected cations, 14 nitrogen-rich energetic salts were synthesized in high yield by metathesis reactions. These salts were fully characterized by (1)H, (13)C NMR, and IR spectroscopy and elemental analysis. Additionally, the structures of the ammonium, 3,4,5-triaminotriazolium, and biguanidinium salts were confirmed by single-crystal X-ray diffraction. Based on experimental and calculated values, the 4-nitramino-3,5-dinitropyrazolate salts show properties, such as decomposition temperatures (115-229 °C), detonation pressures (23.27-37.42 GPa) and velocities (7713-9013 ms(-1)), and impact sensitivities (5-40 J) that place them with energetics such as RDX and TATB.