Co-reporter:Lei Zhang, Ling He, Cheng-Bin Hong, Song Qin and Guo-Hong Tao
Green Chemistry 2015 vol. 17(Issue 12) pp:5154-5163
Publication Date(Web):25 Sep 2015
DOI:10.1039/C5GC01913C
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.
Co-reporter:Ling He, Shun-Ping Ji, Ning Tang, Ying Zhao and Guo-Hong Tao
Dalton Transactions 2015 vol. 44(Issue 5) pp:2325-2332
Publication Date(Web):05 Dec 2014
DOI:10.1039/C4DT03294B
Five hexanitratoneodymate-based rare earth complexes (1–5) were synthesized using a straightforward method. Purple plate crystals of 1 were isolated and the crystal structure was determined by single-crystal X-ray diffraction with respect to the coordination mode of the nitrate anion to the central Nd(III) ion. (1: monoclinic system P21/c, a = 15.9460(3) Å, b = 10.2457(6) Å, c = 33.323(3) Å, β = 91.8108(17)°, V = 3109.11(11) Å3, Z = 4). The central Nd(III) ion is surrounded by six bidentate nitrate ligands, with a major trend towards high symmetry of the [Nd(NO3)6]3− anion as an icosahedron. Thermal properties were determined from differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests. Complexes 3–5 are found to be room temperature liquids, and their excitation and emission spectra were recorded. These complexes exhibit intense near-infrared (NIR) luminescence emission, which originates from interconfigurational f–f transitions 4F3/2→4IJ multiplet (J = 9/2–13/2). These liquid Nd(III) complexes are of interest as potential NIR luminescent soft materials with high thermal stability.
Co-reporter:Ning Tang, Ying Zhao, Ling He, Wen-Li Yuan and Guo-Hong Tao
Dalton Transactions 2015 vol. 44(Issue 19) pp:8816-8823
Publication Date(Web):23 Mar 2015
DOI:10.1039/C5DT00191A
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.
Co-reporter:Yi-Fei Gao, Lei Zhang, Ling He, Ying Zhao, Ning Tang, Wen-Li Yuan and Guo-Hong Tao
RSC Advances 2015 vol. 5(Issue 67) pp:54527-54534
Publication Date(Web):16 Jun 2015
DOI:10.1039/C5RA07415K
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.
Co-reporter:Ying Zhao;Ling He;Ning Tang;Song Qin;Guo-Hong Tao;Fu-Xin Liang
European Journal of Inorganic Chemistry 2015 Volume 2015( Issue 3) pp:542-551
Publication Date(Web):
DOI:10.1002/ejic.201403018
Abstract
A series of luminescent ionic liquids based on pentanitratoeuropate(III) anions combined with imidazolium cations, namely, 1,2,3-trimethylimidazolium {[MC1mim]2[Eu(NO3)5] (1)}, 1,3-dimethylimidazolium {[C1mim]2[Eu(NO3)5] (2)}, 1-ethyl-3-methylimidazolium {[C2mim]2[Eu(NO3)5] (3)}, 1-butyl-3-methylimdazolium {[C4mim]2[Eu(NO3)5] (4)}, 1-hexyl-3-methylimidazolium {[C6mim]2[Eu(NO3)5] (5)}, and 1-methyl-3-octylimidazolium {[C8mim]2[Eu(NO3)5] (6)}, were synthesized. These complexes were characterized by NMR and IR spectroscopy as well as elemental analysis. They exhibit high thermostability and wide liquidus ranges of more than 300 °C. Colorless plate crystals of 1 were isolated, and the crystal structure was determined by single-crystal X-ray diffraction [monoclinic system, C2/c space group with the cell parameters a = 21.6870(6) Å, b = 9.9807(4) Å, c = 15.0267(6) Å, β = 131.140(4)°, Z = 4]. In the [Eu(NO3)5]2– anion, the 10-coordinate EuIII ion is coordinated by five bidentate nitrate ligands and has a highly symmetrical trigonal-bipyramidal geometry. Compounds 1–6 exhibit bright red luminescence of high colorimetric purity. Only two characteristic narrow monochromatic bands, arising from the 5D07FJ (J = 1 and 2) intraconfigurational f–f transitions, were clearly observed in their emission spectra at 298 K. The intense red photoluminescence is still stable at 150 °C. These 10-coordinated EuIII complexes are of interest as potential thermally stable luminescent soft materials.
Co-reporter:Lin-Lin Dong, Ling He, Guo-Hong Tao and Changwei Hu
RSC Advances 2013 vol. 3(Issue 14) pp:4806-4813
Publication Date(Web):29 Jan 2013
DOI:10.1039/C3RA23034A
Ethyl valerate (EV) as a promising fuel additive was produced by esterification of valeric acid with ethanol over Brønsted acidic amino acid ionic liquids. Hammett method and density functional theory (DFT) calculations were preformed to evaluate the acidities of the catalysts. The composition of catalyst, reaction temperature, reaction time, molar ratio of reactants, amount of catalyst, and recycling ability of the catalyst were investigated. Proline bisulfate (ProHSO4) ionic liquid has the highest catalytic activity and the best recyclability under the optimized esterification conditions. A high conversion of valeric acid (>99.9%) was obtained for 7 h at 80 °C, with 100% selectivity of EV. The density, viscosity, melting point, boiling point, elemental analysis and heat of combustion of the EV product were measured. The density of EV is 0.896 g cm−3. The viscosity of EV was 1.7 cP at room temperature. The heating values of EV are 4158.1 kJ mol−1 and 31.9 kJ g−1. EV obtained from esterification has higher energy density than methanol, ethanol, γ-valerolactone, and valeric acid, which illustrates that EV is a promising biofuel candidate.
Co-reporter:Lin-Lin Dong;Ling He;Hang-Yu Liu;Guo-Hong Tao;Fu-De Nie;Ming Huang;Chang-Wei Hu
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 28) pp:5009-5019
Publication Date(Web):
DOI:10.1002/ejic.201300631
Abstract
N,N-Bis(1H-tetrazol-5-yl)amine anions (HBTA–/BTA2–) were used as suitable nitrogen-rich components for the construction of energetic ionic liquids. Seven ionic liquids, namely, 1,3-dimethylimidazolium (1, [C1mim]HBTA), 1-ethyl-3-methylimidazolium (2, [C2mim]HBTA), 1-butyl-3-methylimidazolium (3, [C4mim]HBTA), 1-hexyl-3-methylimidazolium (4, [C6mim]HBTA), 1-methyl-3-octylimidazolium (5, [C8mim]HBTA), and 1,2,3-trimethylimidazolium (6, [C1mmim]HBTA) cations with the HBTA– anion and di-1,2,3-trimethylimidazolium N,N-bis(1H-tetrazol-5-yl)amine (7, [C1mmim]2BTA), were synthesized. All materials were fully characterized by IR and NMR spectroscopy, elemental analysis, and high-resolution mass spectrometry. The crystal structures of 1 and 7 were determined by single-crystal X-ray diffraction [1: monoclinic, P21/n, a = 14.0653(4) Å, b = 6.9507(2) Å, c = 22.4699(7) Å, β = 93.996(3)°, V = 2191.38(12) Å3, Z = 8, ρ = 1.511 g cm–3; 7: monoclinic, P21/c, a = 17.5869(3) Å, b = 12.8757(2) Å, c = 21.9203(6) Å, β = 125.0580(10)°, V = 4063.15(15) Å3, Z = 8, ρ = 1.221 g cm–3]. The nitrogen contents of 1–7 exceed 40 %, and 1 has the highest value of 61.78 %. The ionic liquids 1–7 are thermally stable to 220 °C, and 2–5 are room-temperature ionic liquids. The heats of formation of 1–7 obtained by both experimental and theoretical methods are all positive. The ionic liquids 1–7 are insensitive towards impact (>40 J) and friction (>360 N). They can be ignited in air. These new energetic ionic liquids contain only C, H, and N and are of interest as potential propellants with high energy, high thermal stability, low sensitivity to impact and friction, and environmentally friendly decomposition gases.
Co-reporter:Lin-Lin Dong, Ling He, Guo-Hong Tao, Ming Huang, and Changwei Hu
Journal of Chemical & Engineering Data 2013 Volume 58(Issue 5) pp:1176-1185
Publication Date(Web):April 1, 2013
DOI:10.1021/je301285c
The theoretical enthalpies of formation of 108 [AA]X and [AAE]X type amino acid ionic liquids composed of 12 amino acid cations (Gly+, GlyC1+, Ala+, AlaC1+, Pro+, ProC1+, Phe+, PheC1+, Val+, ValC1+, Leu+, LeuC1+) with 9 different anions (Cl–, BF4–, PF6–, N(CF3SO2)2–, CH3CO2–, CF3CO2–, CF3SO3–, HSO4–, SO42–) were studied. A systematic theoretical study on these amino acid ionic liquids was performed by quantum chemistry calculation using the Gaussian03 program. The geometric optimization and the frequency analyses were 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 MP2/6-311++G** level of theory. The enthalpies of formation of these amino acid ionic liquids were calculated to be from −2577.0 kJ·mol–1 to −311.3 kJ·mol–1. The negative values show their stable thermodynamics status. The energy differences between the predicted enthalpies of formation of each amino acid salt and those of their two neutral precursors were studied. The experimental enthalpies of formation of five amino acid ionic liquids [Gly]Cl, [Ala]Cl, [Ala]HSO4, [Pro]CF3CO2, and [Pro]CF3SO3 were obtained from the corresponding energies of combustion determined by the bomb calorimetry method. The experimental enthalpies of formation are in good agreement with corresponding theoretical results. This study provides an effective theoretical method to predict the thermodynamic stability of the preparation of new amino acid ionic liquids.
Co-reporter:Shun-Ping Ji;Meng Tang;Dr. Ling He ;Dr. Guo-Hong Tao
Chemistry - A European Journal 2013 Volume 19( Issue 14) pp:4452-4461
Publication Date(Web):
DOI:10.1002/chem.201300092
Abstract
The hexanitratolanthanate anion (La(NO3)63−) is an interesting symmetric anion suitable to construct the component of water-free rare-earth-metal ionic liquids. The syntheses and structural characterization of eleven lanthanum nitrate complexes, [Cnmim]3[La(NO3)6] (n=1, 2, 4, 6, 8, 12, 14, 16, 18), including 1,3-dimethylimidazolium hexanitratolanthanate ([C1mim]3[La(NO3)6], 1), 1-ethyl-3-methylimidazolium hexanitratolanthanate ([C2mim]3[La(NO3)6], 2), 1-butyl-3-methylimidazolium hexanitratolanthanate ([C4mim]3[La(NO3)6], 3), 1-isobutyl-3-methylimidazolium hexanetratolanthanate ([isoC4mim]3[La(NO3)6], 4), 1-methyl-3-(3′-methylbutyl)imidazolium hexanitratolanthanate ([MC4mim]3[La(NO3)6], 5), 1-hexyl-3-methylimidazolium hexanitratolanthanate ([C6mim]3[La(NO3)6], 6), 1-methyl-3-octylimidazolium hexanitratolanthanate ([C8mim]3[La(NO3)6], 7), 1-dodecyl-3-methylimidazolium hexanitratolanthanate ([C12mim]3[La(NO3)6], 8), 1-methyl-3-tetradecylimidazolium hexanitratolanthanate ([C14mim]3[La-(NO3)6], 9), 1-hexadecyl-3-methylimid-azolium hexanitratolanthanum ([C16dmim]3[La(NO3)6], 10), and 1-methyl-3-octadecylimidazolium hexanitratolanthanate ([C18mim]3[La(NO3)6], 11) are reported. All new compounds were characterized by 1H and 13C NMR, and IR spectroscopy as well as elemental analysis. The crystal structure of compound 1 was determined by using single-crystal X-ray diffraction, giving the following crystallographic information: monoclinic; P21/c; a=15.3170 (3), b=14.2340 (2), c=13.8954(2) Å; β=94.3453(15)°, V=3020.80(9) Å3, Z=4, ρ=1.764 g cm−3. The coordination polyhedron around the lanthanum ion is rationalized by six nitrate anions with twelve oxygen atoms. No hydrogen-bonding network or water molecule was found in 1. The thermodynamic stability of the new complexes was investigated by using thermogravimetric analysis (TGA). The water-free hexanitratolanthanate ionic liquids are thermal and moisture stable. Four complexes, namely complexes 8–11, were found to be ionic liquid crystals by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). They all present smectic A liquid-crystalline phase.
Co-reporter:Guo-Hong Tao;Meng Tang;Ling He;Shun-Ping Ji;Fu-De Nie;Ming Huang
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 18) pp:3070-3078
Publication Date(Web):
DOI:10.1002/ejic.201200065
Abstract
Eight 5-aminotetrazolate (AT) salts based on the 1,2,3-trimethylimidazolium (1), 1,3-dimethylimidazolium (2), 1-ethyl-3-methylimidazolium (3), 1-butyl-3-methylimidazolium (4), 1-isobutyl-3-methylimidazolium (5), 1-(3′-methylbutyl)-3-methylimidazolium (6), 1-hexyl-3-methylimidazolium (7) and 1-methyl-3-octylimidazolium (8) cations have been synthesized in high yields and fully characterized by IR and NMR spectroscopy and elemental analysis. White plate crystals of 1 were isolated in methanol/diethyl ether and crystallized. Both the AT anion and the 1,2,3-trimethylimidazolium cation in 1 were delocalized. Differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests were used to assess the thermal stabilities of the AT salts. These salts decomposed within the temperature range 230 °C–262 °C. Salts 3–8 are very fluent room-temperature ionic liquids, whose glass transition temperatures are low. Their viscosities at 30 °C are in the range from 92 cP to 208 cP. A correlation between the viscosity and temperature was found, and the ionic liquids to do not display an Arrhenius temperature behaviour. In addition, the standard enthalpies of formation of salts 1–8 were investigated and analyzed by the theoretical methods. Salt 2 with the 1,3-dimethylimidazolium cation gave the highest positive enthalpy of formation. For the assessment of the energetic character of the AT salts, impact sensitivities and friction sensitivities were recorded. These AT salts are insensitive to impact (>40 J) and friction (>360 N) confirmed by UN standards. The reactions of these AT salts with 100 % HNO3 were also determined.
Co-reporter:Jing-Fang Zhu, Ling He, Lei Zhang, Ming Huang, and Guo-Hong Tao
The Journal of Physical Chemistry B 2012 Volume 116(Issue 1) pp:113-119
Publication Date(Web):December 12, 2011
DOI:10.1021/jp209649h
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.
Co-reporter:Ning Tang, Ying Zhao, Ling He, Wen-Li Yuan and Guo-Hong Tao
Dalton Transactions 2015 - vol. 44(Issue 19) pp:NaN8823-8823
Publication Date(Web):2015/03/23
DOI:10.1039/C5DT00191A
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.
Co-reporter:Ling He, Shun-Ping Ji, Ning Tang, Ying Zhao and Guo-Hong Tao
Dalton Transactions 2015 - vol. 44(Issue 5) pp:NaN2332-2332
Publication Date(Web):2014/12/05
DOI:10.1039/C4DT03294B
Five hexanitratoneodymate-based rare earth complexes (1–5) were synthesized using a straightforward method. Purple plate crystals of 1 were isolated and the crystal structure was determined by single-crystal X-ray diffraction with respect to the coordination mode of the nitrate anion to the central Nd(III) ion. (1: monoclinic system P21/c, a = 15.9460(3) Å, b = 10.2457(6) Å, c = 33.323(3) Å, β = 91.8108(17)°, V = 3109.11(11) Å3, Z = 4). The central Nd(III) ion is surrounded by six bidentate nitrate ligands, with a major trend towards high symmetry of the [Nd(NO3)6]3− anion as an icosahedron. Thermal properties were determined from differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests. Complexes 3–5 are found to be room temperature liquids, and their excitation and emission spectra were recorded. These complexes exhibit intense near-infrared (NIR) luminescence emission, which originates from interconfigurational f–f transitions 4F3/2→4IJ multiplet (J = 9/2–13/2). These liquid Nd(III) complexes are of interest as potential NIR luminescent soft materials with high thermal stability.
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