Amino acid ionic liquids (AAILs) [AA]X based on amino acid cations are a kind of typical “bio-base” protic ionic liquids (PILs), which are supposed to be acidic ionic liquids. The Brønsted acidity of [AA]X PILs at room temperature was systematically studied for the first time. Acid dissociation constants (pKa) of [AA]X were determined by the potentiometric titration method. The first acid dissociation constants (pKa1) are from 1.98 to 2.42. The actual pH values of [AA]X (0.010 mol L−1) obtained from a pH meter are from 2.26 to 2.44 which are slightly higher than the calculated pH values according to the above experimental pKa1. The Hammett method performed on UV/Vis spectra with p-nitroaniline as the indicator was used to determine the acidic strength of [AA]X. Their H0 values (0.010 mol L−1) are in the range from 2.10 to 2.44. Various frameworks of amino acid cations and five anions (including nitrate (NO3−), chloride (Cl−), perchlorate (ClO4−), trifluoromethanesulfonate (OTf−) and trifluoroacetate (TfA−) anions) were used to investigate the cationic and anionic effect on the acidity of AAILs. The Brønsted acidity of AAILs depends on the cationic structure, the type of anion and the concentration of [AA]X. In addition, the theoretical pKa1 values were studied by using the cluster-continuum model using the density functional theory (DFT) method. The experimental and theoretical results showed that [AA]X PILs have a stronger Brønsted acidity than the common PILs prepared by one-pot syntheses.

Sm(III)-based ionic liquids incorporating hexanitratosamarate(III) anions were obtained and fully characterized as novel Sm(III)-containing organic complexes. The structure of the ionic liquids was determined by single-crystal X-ray diffraction (1: monoclinic system C2/c space group with cell parameters: a = 19.5624(4) Å, b = 10.11895(18) Å, c = 33.2256(6) Å, β = 101.2912(18)°, Z = 8). The central Sm(III) ion is 12-coordinated by six bidentate nitrate ligands with twelve oxygen donors to form a [Sm(NO3)6]3− anion. The low melting point, high thermostability and wide liquid range of these ionic liquids were determined in detail. All the complexes 1–5 display orange luminescence, rather than red luminescence as in most Sm(III)-containing organic complexes. Three characteristic monochromatic bands and an intense emission, derived from 4G5/2→6HJ (J = 5/2, 7/2, and 9/2) intraconfigurational f–f transitions, were revealed. All these complexes exhibit long luminescence lifetimes.

Five energetic ionic liquids of 5-nitroaminotetrazolate anion (NAT) combined with 1,3-dimethylimidazolium (1), 1-ethyl-3-methylimidazolium (2), 1-butyl-3-methylimidazolium (3), 1-hexyl-3-methylimidazolium (4), and 1-methyl-3-octylimidazolium (5) cations were synthesized in high yields and fully characterized by IR, NMR and elemental analysis. Colorless block crystals of 1 were isolated in methanol/ethanol and crystallized in the orthorhombic system Fdd2(43) (a = 49.337(3) Å, b = 20.9073(12) Å, c = 3.6993(2) Å, V = 3815.84(38) Å3, Z = 16). The ionic liquids 1–5 are thermally stable at temperatures higher than 200 °C. Among them, 2–5 are found to be room temperature ionic liquids. The heats of formation of 1–5 obtained by both experimental and theoretical methods are all positive. 1 possesses the highest value of 194.6 kJ mol−1 and 0.86 kJ g−1. These novel NAT energetic ionic liquids contain only C, H, N and O elements. The CHNO type ionic liquids 1–5 are insensitive towards impact (>40 J) and friction (>360 N). They showed good combustion characteristics after being ignited by a flame. They are of interest as liquid energetic materials with modestly high energy, high thermal stability, and good insensitivity to impact and friction, as well as environmentally friendly decomposition gases.

•We have developed a facile sol–gel method to synthesize CuS NCs.•The pyridine capped CuS NCs can be used directly as interfacial layer without ligand-exchange.•The hydrophilic CuS NCs can be exchanged with OAm and OA rapidly at room temperature and present hydrophobic characteristic.•The CuS NCs possess the superior interfacial property and can be processed in lower temperature than other metal oxide.CuS NCs were synthesized via a facile sol–gel method without post-thermal treatment. The as-prepared CuS NCs were analyzed and confirmed by XRD, HR-TEM, EDS and XPS as hexagonal covellite CuS. The average diameter of the samples was about 3 nm with narrow size distribution. CuS NCs can form a thin and smooth film without ligand-exchange that can be used as hole transport layer in organic solar cell. These hydrophilic CuS NCs with pyridine ligands can be exchanged with OAm and OA rapidly at room temperature and present hydrophobic characteristic, resulting in forming oil-soluble CuS NCs. This makes it possible tuning the surface property of CuS NCs and has the potential application for different fields.

Several stable guanidinium, triazolium, and tetrazolium dinitromethanide salts with high nitrogen content, good detonation properties, and concomitant low impact sensitivities are potential energetic materials.

The experimental and theoretical enthalpies of formation of several structural-similar glycine-based sulfate/bisulfate amino acid ionic liquids including glycine sulfate (Gly2SO4, 1), glycine bisulfate (GlyHSO4, 2), N,N-dimethylglycine sulfate ([DMGly]2SO4, 3), N,N-dimethylglycine bisulfate ([DMGly]HSO4, 4), N,N-dimethylglycine methyl ester sulfate ([DMGlyC1]2SO4, 5), N,N-dimethylglycine methyl ester bisulfate ([DMGlyC1]HSO4, 6), N,N,N-trimethylglycine methyl ester sulfate ([TMGlyC1]2SO4, 7), and N,N,N-trimethylglycine methyl ester bisulfate ([TMGlyC1]HSO4, 8) were studied. Their experimental enthalpies of formation were obtained from the corresponding energies of combustion determined by the bomb calorimetry method. The enthalpies of formation of these amino acid ionic liquids are in the range from −1406 kJ mol–1 to −1128 kJ mol–1. Systematic theoretical study on these amino acid ionic liquids were performed by quantum chemistry calculation using the Gaussian03 suite of programs. The geometric optimization and the frequency analyses are carried out using the B3LYP method with the 6-31+G** basis set. Their calculated enthalpies of formation were derived from the single point energies carried out with the HF/6-31+G**, B3LYP/6-31+G**, B3LYP/6-311++G**, and MP2/6-311++G** level of theory, respectively. The relevance of experimental and calculated enthalpies of formation was studied. The calculated enthalpies of formation are in good agreement with their experimental data in less than 3% error.

Sm(III)-based ionic liquids incorporating hexanitratosamarate(III) anions were obtained and fully characterized as novel Sm(III)-containing organic complexes. The structure of the ionic liquids was determined by single-crystal X-ray diffraction (1: monoclinic system C2/c space group with cell parameters: a = 19.5624(4) Å, b = 10.11895(18) Å, c = 33.2256(6) Å, β = 101.2912(18)°, Z = 8). The central Sm(III) ion is 12-coordinated by six bidentate nitrate ligands with twelve oxygen donors to form a [Sm(NO3)6]3− anion. The low melting point, high thermostability and wide liquid range of these ionic liquids were determined in detail. All the complexes 1–5 display orange luminescence, rather than red luminescence as in most Sm(III)-containing organic complexes. Three characteristic monochromatic bands and an intense emission, derived from 4G5/2→6HJ (J = 5/2, 7/2, and 9/2) intraconfigurational f–f transitions, were revealed. All these complexes exhibit long luminescence lifetimes.

Several stable guanidinium, triazolium, and tetrazolium dinitromethanide salts with high nitrogen content, good detonation properties, and concomitant low impact sensitivities are potential energetic materials.