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Biomedical subjects

Jean'ne M Shreeve

Publications and source records attributed to Jean'ne M Shreeve.

At least 19 recordsLinked to original sources
PubMed2006

Energetic bicyclic azolium salts.

Bicyclic azoles, 2-methyl-5-(imidazol-1-yl)-2H-tetrazole (1), 2-methyl-5-(1,2,4-triazol-1-yl)-2H-tetrazole (4), 1-methyl-5-(imidazol-1-yl)-1H-tetrazole (7), 1-methyl-5-(1,2,4-triazol-1-yl)-1H-tetrazole (10), 1-methyl-4-nitro-2-(imidazol-1-yl)-1H-imidazole (13), and 1-methyl-4-nitro-2-(1,2,4-triazol-1-yl)-1H-imidazole (16) were prepared. Their thermally stable azolium salts, 3, 6, 9, 12, 15, and 18-21, with densities ranging between 1.519-1.674 g cm-3, were synthesized by quaternization with nitric or perchloric acid or with iodomethane followed by metathesis reactions with silver nitrate and silver perchlorate. The structures of 12 b and 21 b were confirmed by single-crystal X-ray analysis. The standard enthalpies of formation for some of the new salts were calculated by using the computationally feasible DFT(B3LYP) and MP2 methods in conjunction with an empirical approach based on densities of salts. The calculated values range from DeltaHdegreef=209.9 (21 a) to 412.3 (12 b) kJ mol-1 in which the experimental densities are >1.515 g cm-3.

Journal Article↗
PubMed2006

Syntheses and characterization of unsymmetric dicationic salts incorporating imidazolium and triazolium functionalities.

A series of both imidazolium- and triazolium-based unsymmetric dicationic salts with alkyl and polyfluoroalkyl substituents were prepared and characterized. Most of them can be classified as ionic liquids (MP < 100 degrees C). Key physical properties, such as melting point, thermal stability, density, and solubility in common solvents were determined and were compared with those of the related monocationic imidazolium- or triazolium-based salts. The effects of anions and substituents bonded to the triazolium and imidazolium cations on these properties were examined. 1-(3-Butyl-imidazolium-1-yl)methylene-(4-butyl-1,2,4-triazolium diiodide) (2d), the precursor of 1-(3-butylimidazolium-1-yl)methylene-(4-butyl-1,2,4-triazolium) bi[bis(trifluoromethanesulfonyl)amide] (3d), reacted with Pd(OAc)(2) at 120 degrees C to generate a binuclear palladium(II) dicarbene complex. The palladium(II) complex was characterized by single-crystal X-ray diffraction analysis and was used as a catalyst precursor for palladium-catalyzed Heck cross-coupling reactions in 3d. Preliminary results show that 3d could serve as both the solvent and catalyst support in the catalytic reactions.

Journal Article↗
PubMed2006

Energetic nitrogen-rich salts and ionic liquids.

Energetic salts offer many advantages over conventional energetic molecular compounds. The use of nitrogen containing anions and cations contributes to high heats of formations and high densities. Their low carbon and hydrogen content gives rise to a good oxygen balance. The decomposition of these compounds is predominantly through the generation of dinitrogen which makes them very promising candidates for highly energetic materials for industrial or military applications.

Journal Article↗
PubMed2006

Pyrazolyl-functionalized 2-methylimidazolium-based ionic liquids and their palladium(II) complexes as recyclable catalysts.

A series of pyrazolyl- and 3,5-dimethylpyrazolyl-functionalized 2-methylimidazolium-based salts have been prepared through neat reactions of 1-pyrazolylmethylene-2-methylimidazole and 1-(3,5-dimethylpyrazolylmethylene)-2-methylimidazole with alkyl or polyfluoroalkyl iodides or 1-bromohexane, followed by anion exchange with LiN(SO2CF3)2 or KPF6. Their thermal properties were determined by DSC and TGA. Most of the bis(trifluoromethanesulfonyl)amide salts are room temperature ionic liquids. The influence of anions and of the structural variation in the 2-methylimidazolium-based cations on the physicochemical properties is discussed. These salts reacted easily with palladium(II) chloride to generate mononuclear palladium ionic liquid complexes. The catalytic activity and recyclability of the palladium complexes in the corresponding ionic liquids were preliminarily examined using Heck, Suzuki and Sonogashira cross-coupling reactions in the absence of phosphine ligands.

Journal Article↗
PubMed2006

Coordination networks with fluorinated backbones.

Fluorine-containing ligands 2,3,5,6-tetrafluoro-1,4-bis(imidazol-1-yl-methyl)benzene (1) and 2,3,5,6-tetrafluoro-1,4-bis(2-methylimidazol-1-yl-methyl)benzene (2) were prepared and coordinated with AgNO3, Co(ClO4)2 x 6 H2O, and Cd(NO3)2 x 4 H2O, respectively, to form the following structures: 3D channel polymer [Ag2(1)2(NO3)2 x H2O x MeOH]n (3), 2D sheet polymer [Co(1)3(ClO4)2]n (4), 1D chain polymer [Cd(1)3(NO3)2 x 4 H2O]n (5), and a 2D herringbone sheet polymer [Ag(2)NO3 x 1.5 MeOH]n (6). The solid-state crystal structures of 3-6 were studied by single-crystal X-ray crystallography.

Crystallography, X-Ray↗
PubMed2005

Energetic quaternary salts containing bi(1,2,4-triazoles).

New energetic salts (2, 3, 9, 10, and 11) were synthesized via the protonation of 4,4'-bi(1,2,4-triazole) or N-4-(1,2,4-triazole)-N-3-(4-methyl-1,2,4-triazole)amine with nitric acid or perchloric acid or 5-nitro-tetrazole. The structures of 4,4'-bi(1,2,4-triazolium) nitrate (2), N,N-dimethyl-N'-(5-methyl-tetrazole)methanimidamide (8), and N-4-(1,2,4-triazole)-N-3-(4-methyl-1,2,4-triazolium)amine perchlorate (10) were confirmed by a single-crystal X-ray analysis. The physical properties and heats of combustion of the new ionic salts were measured, and the heats of formation were also determined.

Journal Article↗
PubMed2005

Energetic azolium azolate salts.

Energetic salts comprising substituted imidazolium and 1,2,4-triazolium cations and 4,5-dinitro-imidazolate and 5-nitrotetrazolate anions were synthesized and characterized. On the basis of experimentally obtained heats of combustion, the calculated heats of formation range from deltaHf(o) degrees = 80 (3) to 1071 kJ/mol (13). Imidazolate salts are more dense but have lower heats of formation than their tetrazolate analogues. Salts 4, 5, 8, and 11-14 fall into the ionic liquid class (mp < 100 degrees C). The structure of 1,2,4-triazolium 5-nitrotetrazolate (10) was confirmed by X-ray analysis.

Journal Article↗
PubMed2005

Synthesis of 2,2'-biimidazolium-based ionic liquids: use as a new reaction medium and ligand for palladium-catalyzed suzuki cross-coupling reactions.

Neat reactions of 2,2'-biimidazole with an excess of alkyl or polyfluoroalkyl iodides at 140 degrees C, followed by anion exchange with LiN(SO(2)CF(3))(2) or KPF(6), gave the diquaternary salts 3a-k in >80% yields. However, by controlling the reaction stoichiometry, 2,2'-biimidazole can also be monoquaternized with the same electrophiles at 100 degrees C under similar conditions. Subsequent metathesis reactions with LiN(SO(2)CF(3))(2) or KPF(6) resulted in the ionic liquids 4a-m in high yields. Thermal properties were determined with a differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA). Most of the monoquaternary salts are room-temperature ionic liquids. 1,3,1'-Tributyl-2,2'-biimidazolium hexafluorophosphate was demonstrated to be an excellent solvent and ligand for palladium-catalyzed Suzuki cross-coupling reactions. The catalytic ionic liquid system may be recycled at least 14 times without a significant decrease in catalytic performance.

Journal Article↗
PubMed2005

Guanidinium-based ionic liquids.

Cyclic (subset=N+<, subset = imidazolidine 3 and 4, hexahydro-pyrimidine 7 and 8, tetrahydro-1,3,5-oxadiazine 12, and triazoline 15 and 16) and acyclic [(R2N)2C=N+<, 19] guanidinium-based salts were synthesized via the quaternization of guanidine derivatives with nitric or perchloric acid or with iodomethane followed by metathesis reaction with silver nitrate, silver perchlorate, or ammonium dinitroamide. The structure of 15d was confirmed by single-crystal X-ray analysis. Most of the salts exhibited low melting points and good thermal stabilities. Their densities range between 1.2 and 1.5 g/cm3. Standard molar enthalpies of formation were calculated from experimentally determined constant-volume combustion energies obtained using an oxygen bomb calorimeter.

Journal Article↗
PubMed2004

Energetic salts from N-aminoazoles.

New energetic salts (2, 3, 5, 6, 13, 14, 21, 22) were synthesized via the quaternization of derivatives of N-aminoazoles with nitric or perchloric acid or with iodomethane followed by metathesis reaction with silver nitrate or silver perchlorate. The structure of 2-amino-4,5-dimethyltetrazolium nitrate (21) was confirmed by single-crystal X-ray analysis. Most of the salts exhibit good thermal stabilities and low melting points. By using experimentally determined constant volume combustion energies, the standard molar enthalpies of formation were derived on the basis of designed Hess thermochemical cycles.

Journal Article↗