Azidomethyl-bisoxadiazol-linked-1,2,3-triazole-(ABT)-based potential liquid propellant and energetic plasticizer

A scalable synthesis of azidomethyl bisoxadiazol linked-1,2,3-triazole-(ABT) based potential liquid propellant and energetic plasticizer is obtained from commercially available diaminomaleonitrile in excellent yield. Newly synthesized compounds were fully characterized by various spectroscopic techniques. These materials exhibit good densities (1.77 g cm-3) and high thermal stabilities (Td = 181 °C). Compound 5 has good detonation properties (5, P = 20.81 GPa, D = 7516 ms-1) and propulsive properties (Isp (neat) = 210 s). These are superior to TNT and GAP and comparable to BAMOD, making them potential green liquid rocket propellants and energetic plasticizers.

Green Light Promoted Iridium(III)/Copper(I)-Catalyzed Addition of Alkynes to Aziridinoquinoxalines Through the Intermediacy of Azomethine Ylides

This manuscript describes the development of alkyne addition to the aziridine moiety of aziridinoquinoxalines using dual Ir(III)/Cu(I) catalytic system under green light-emitting diode (LED) photolysis (λmax =525 nm). This mild method features high levels of chemo- and regioselectivity and was used to generate 30 highly functionalized substituted dihydroquinoxalines in 36-98 % yield. This transformation was also carried asymmetrically using phthalazinamine-based chiral ligand to provide 9 chiral addition products in 96 : 4 to 86 : 14 e.r. The experimental and quantum chemical explorations of this reaction suggest a mechanism that involves Ir(III)-catalyzed triplet energy transfer followed by a ring-opening reaction ultimately leading to the formation of azomethine ylide intermediates. These azomethine intermediates undergo sequential protonation/copper(I) acetylide addition to provide the products.

Nitroiminotriazole (NIT) based potential solid propellants: synthesis, characterization, and applications

Nitroimino (R = N-NO2) energetic material is a unique class of high energy density materials (HEDM). Synthesis and characterization of insensitive nitroimino compounds are a major challenge. Here triazole-based nitroimino compounds and their high-nitrogen green energetic salts in excellent yields are described. These materials exhibit high positive heats of formation (7.84 to 735.29 kJ mol-1), good densities (1.66 to 1.98 g cm-3), suitable detonation properties (P = 22.02 to 31.88 GPa; D = 7472 to 8936 ms-1) and high ballistic properties (Isp 205.66 to 295.35 s; C* = 1065 to 1832 ms-1) with good thermal (Td = 136-378 °C) and mechanical stabilities (IS = 10-40 J and FS = 120-360 N).

Ortho-Alkoxy-benzamide Directed Formation of a Single Crystalline Hydrogen-bonded Crosslinked Organic Framework and Its Boron Trifluoride Uptake and Catalysis

Boron trifluoride (BF3 ) is a highly corrosive gas widely used in industry. Confining BF3 in porous materials ensures safe and convenient handling and prevents its degradation. Hence, it is highly desired to develop porous materials with high adsorption capacity, high stability, and resistance to BF3 corrosion. Herein, we designed and synthesized a Lewis basic single-crystalline hydrogen-bond crosslinked organic framework (HC OF-50) for BF3 storage and its application in catalysis. Specifically, we introduced self-complementary ortho-alkoxy-benzamide hydrogen-bonding moieties to direct the formation of highly organized hydrogen-bonded networks, which were subsequently photo-crosslinked to generate HC OFs. The HC OF-50 features Lewis basic thioether linkages and electron-rich pore surfaces for BF3 uptake. As a result, HC OF-50 shows a record-high 14.2 mmol/g BF3 uptake capacity. The BF3 uptake in HC OF-50 is reversible, leading to the slow release of BF3 . We leveraged this property to reduce the undesirable chain transfer and termination in the cationic polymerization of vinyl ethers. Polymers with higher molecular weights and lower polydispersity were generated compared to those synthesized using BF3  ⋅ Et2 O. The elucidation of the structure-property relationship, as provided by the single-crystal X-ray structures, combined with the high BF3 uptake capacity and controlled sorption, highlights the molecular understanding of framework-guest interactions in addressing contemporary challenges.

Manipulating nitration and stabilization to achieve high energy

Nitro groups have played a central and decisive role in the development of the most powerful known energetic materials. Highly nitrated compounds are potential oxidizing agents, which could replace the environmentally hazardous used materials such as ammonium perchlorate. The scarcity of azole compounds with a large number of nitro groups is likely due to their inherent thermal instability and the limited number of ring sites available for bond formation. Now, the formation of the first azole molecule bonded to seven nitro groups, 4-nitro-3,5-bis(trinitromethyl)-1H-pyrazole (4), by the stepwise nitration of 3,5-dimethyl-1H-pyrazole is reported. Compound 4 exhibits exceptional physicochemical properties with a positive oxygen balance (OBCO2 = 13.62%) and an extremely high calculated density (2.04 g cm-3 at 100 K). This is impressively high for a C, H, N, O compound. This work is a giant step forward to highly nitrated and dense azoles and will accelerate further exploration in this challenging field.

Tripodal Organic Cages with Unconventional CH···O Interactions for Perchlorate Remediation in Water

Perchlorate anions used in industry are harmful pollutants in groundwater. Therefore, selectively binding perchlorate provides solutions for environmental remediation. Here, we synthesized a series of tripodal organic cages with highly preorganized Csp3-H bonds that exhibit selectively binding to perchlorate in organic solvents and water. These cages demonstrated binding affinities to perchlorate of 105-106 M-1 at room temperature, along with high selectivity over competing anions, such as iodide and nitrate. Through single crystal structure analysis and density functional theory calculations, we identified unconventional Csp3-H···O interactions as the primary driving force for perchlorate binding. Additionally, we successfully incorporated this cage into a 3D-printable polymer network, showcasing its efficacy in removing perchlorate from water.

C-H···π interactions disrupt electrostatic interactions between non-aqueous electrolytes to increase solubility

Grid-scale energy storage applications, such as redox flow batteries, rely on the solubility of redox-active organic molecules. Although redox-active pyridiniums exhibit exceptional persistence in multiple redox states at low potentials (desirable properties for energy storage applications), their solubility in non-aqueous media remains low, and few practical molecular design strategies exist to improve solubility. Here we convey the extent to which discrete, attractive interactions between C-H groups and π electrons of an aromatic ring (C-H···π interactions) can describe the solubility of N-substituted pyridinium salts in a non-aqueous solvent. We find a direct correlation between the number of C-H···π interactions for each pyridinium salt and its solubility in acetonitrile. The correlation presented in this work highlights a consequence of disrupting strong electrostatic interactions with weak dispersion interactions, showing how minimal structural change can dramatically impact pyridinium solubility.

Energetic performance of trinitromethyl nitrotriazole (TNMNT) and its energetic salts

Little is known about trinitromethyl nitrotriazole (TNMNT) since the crystal structure, density, energetic performance, and thermal properties have not been determined. A detailed characterization of TNMNT and its hydrazinium and potassium salts and their potential as solid propellants and oxidizers has been established. TNMNT exhibits a high density (1.96 g cm-3) and positive enthalpy of formation (ΔHf = +84.79 kJ mol-1). TNMNT and its hydrazinium and potassium salts illustrate excellent detonation properties (P = 34.24 to 36.22 GPa, D = 8899 to 9031 ms-1). TNMNT and its hydrazinium salt exhibit outstanding propulsive properties (Isp = 247.28 to 271.19 s), and these are superior to AP (Isp = 156.63 s) and ADN (Isp = 202.14 s). The results suggest opening the door to utilizing TNMNT and its energetic salts in solid rocket propulsion.

Trinitromethyl-triazolone (TNMTO): a highly dense oxidizer

A scalable synthesis of 5-(trinitromethyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (TNMTO) is possible from commercially available 2-methylpyrimidine-4,6-diol. It exhibits high density (1.90 g cm-3) with comparably low thermal stability (Td = 80 °C) and positive oxygen balance (OBco = 20.51%, OBCO2 = 0.0%). TNMTO has an attractive combination of detonation properties (P = 35.01 GPa, D = 8997 ms-1) and propulsive properties (Isp(neat) = 251.85 s, ρIsp(neat) = 478.52 gs cm-3, ). These are superior to ammonium dinitroamide (ADN), 2,2,2-tetranitroacetimidic acid (TNAA) and ammonium perchlorate (AP), making it a potential green oxidizer in solid rocket propulsion.

Crystal structure of a (carb-oxy-meth-yl)tri-ethyl-aza-nium bromide-2-(tri-ethyl-aza-n-ium-yl)acetate (1/1) hydrogen-bonded dimer

The title compound, C8H18NO2 +·Br-·C8H17NO2, crystallizes as the bromide salt of a 50:50 mixture of (tri-ethyl-azaniumyl)-carb-oxy-lic acid and the zwitterionic (tri-ethyl-azaniumyl)-carboxyl-ate. The two organic entities are linked by a half-occupied bridging carb-oxy-lic acid hydrogen atom that is hydrogen-bonded to the carboxyl-ate group of the second mol-ecule. The tetra-lkyl-ammonium group adopts a nearly perfect tetra-hedral shape around the nitro-gen atom with bond lengths that agree with known values. The carb-oxy-lic acid/carboxyl-ate group is oriented anti to one of the ethyl groups on the ammonium group, and the carbonyl oxygen atom is engaged in intra-molecular C-H⋯O hydrogen bonds.

A Dihydrazone as a Remarkably Nitrogen-Rich Thermostable and Insensitive Energetic Material

Hydrogen bonds (H-bonds) in energetic compounds have a very pronounced effect on physicochemical properties such as density, thermal stability, sensitivity, and solubility. Now a strategy to synthesize nitrogen-rich energetic materials with overall good properties, which stem from the synergetic effects of inter- or intramolecular H-bonds, is reported. 1,2-Dihydrazono-1,2-di(1H-tetrazol-5-5-yl)ethane (4), a new thermostable and insensitive material, is obtained from the reaction of dioxime (2) with hydrazine hydrate. The exchange of the oxime (NOH) with the hydrazone (NNH2) functionality results in the reduced acidic character and low solubility in water, which make it remarkably suitable for practical use. While the detonation velocity of 4 is comparable with RDX, it has an advantage of high nitrogen content (76%) and high thermal stability (275 °C) and is insensitive toward external stimuli.

Design and Synthesis of High-Performance Planar Explosives and Solid Propellants with Tetrazole Moieties

A straightforward synthetic strategy for newly designed nitrogen-rich planar explosives and solid propellants is reported. These materials exhibit high densities (1.69-1.95 g cm^-3), high positive enthalpies of formation (approaching 1149.21 kJ mol^-1), promising energetic properties (P = 26.36-33.78 GPa, D = 8258-9518 m s^-1), acceptable thermal stabilities (T_d = 132-277 °C), good sensitivities (IS = 4-40 J, FS = 60-360 N) and excellent propulsive performance (Isp = 176.80-253.06 s).

Thiol and H2S-Mediated NO Generation from Nitrate at Copper(II)

Reduction of nitrate is an essential, yet challenging chemical task required to manage this relatively inert oxoanion in the environment and biology. We show that thiols, ubiquitous reductants in biology, convert nitrate to nitric oxide at a Cu(II) center under mild conditions. The β-diketiminato complex [Cl₂NN_F6]Cu(κ²-O₂NO) engages in O-atom transfer with various thiols (RSH) to form the corresponding copper(II) nitrite [Cu^II](κ²-O₂N) and sulfenic acid (RSOH). The copper(II) nitrite further reacts with RSH to give S-nitrosothiols RSNO and [Cu^II]₂(μ-OH)₂ en route to NO formation via [Cu^II]-SR intermediates. The gasotransmitter H₂S also reduces nitrate at copper(II) to generate NO, providing a lens into NO₃^-/H₂S crosstalk. The interaction of thiols with nitrate at copper(II) releases a cascade of N- and S-based signaling molecules in biology.

Crystal structure of tert-butyl 3,6-diiodocarbazole-9-carboxylate

The molecular structure of tert-butyl 3,6-diiodocarbazole-9-carboxylate, C17H15I2NO2, features a nearly planar 13-membered carbazole ring with C—I bond lengths of 2.092 (4) and 2.104 (4) Å. The carbamate group has key bond lengths of 1.404 (6) Å (N—C), 1.330 (5) Å (O—C), and 1.201 (6) Å (C=O). The crystal contains intermolecular π–π interactions, as well as both type I and type II intermolecular I...I interactions.

Design and synthesis of phenylene-bridged isoxazole and tetrazole-1-ol based energetic materials of low sensitivity

A variety of phenylene-bridged isoxazole and tetrazole-1-ol based green energetic materials was synthesized, for the first time, in good to excellent yields. The structures of the newly synthesized compounds were confirmed by spectroscopic techniques, elemental analysis, and single-crystal X-ray analysis. The value of the present work is that all newly synthesized compounds have good thermal stabilities ranging between 167-340 °C and acceptable densities between 1.51 g cm^-3 to 1.82 g cm^-3. Detailed computational insight into the energetic properties of the new compounds shows that they have good energetic properties (propulsive and ballistic) with excellent thermal and mechanical stabilities which makes them promising candidates for solid propulsion systems. Compounds 5, 12 and 14 are the superior candidates as melt-castable energetic materials.

Bisnitramide-Bridged N-Substituted Tetrazoles with Balanced Sensitivity and High Performance

In this study, a simple synthetic strategy for bridged bis(nitramide)-based N-substituted tetrazoles is described. All new compounds were isolated and fully characterized by sophisticated analytical techniques. The structures of the intermediate derivative and two final compounds were determined by single-crystal X-ray data. The structures of the intermediate derivative and two final compounds were determined by single crystal X-ray data. Thermostabilities and energetic properties of new bridged bisnitramide-based N-substituted tetrazoles were discussed and compared with known materials.

A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model

This paper compares variations on a structure model derived from an X-ray diffraction data set from a solid solution of chalcogenide derivatives of cis-1,2-bis-(di-phenyl-phosphan-yl)ethyl-ene, namely, 1,2-(ethene-1,2-di-yl)bis-(di-phenyl-phoshpine sulfide/selenide), C₂₆H₂₂P₂S_1.13Se_0.87. A sequence of processes are presented to ascertain the composition of the crystal, along with strategies for which aspects of the model to inspect to ensure a chemically and crystallographically realistic structure. Criteria include mis-matches between F _obs ² and F _calc ², plots of |F _obs| vs |F _calc|, residual electron density, checkCIF alerts, pitfalls of the OMIT command used to suppress ill-fitting data, comparative size of displacement ellipsoids, and critical inspection of inter-atomic distances. Since the structure is quite small, solves easily, and presents a number of readily expressible refinement concepts, we feel that it would make a straightforward and concise instructional piece for students learning how to determine if their model provides the best fit for the data and show students how to critically assess their structures.

Molecular Switch Cobalt Redox Shuttle with a Tunable Hexadentate Ligand

Strong-field hexadentate ligands were synthesized and coordinated to cobalt metal centers to result in three new low-spin to low-spin Co(III/II) redox couples. The ligand backbone has been modified with dimethyl amine groups to result in redox potential tuning of the Co(III/II) redox couples from -200 to -430 mV versus Fc^+/0. The redox couples surprisingly undergo a reversible molecular switch rearrangement from five-coordinate Co(II) to six-coordinate Co(III) despite the ligands being hexadentate. The complexes exhibit modestly faster electron self-exchange rate constants of 2.2-4.2 M^-1 s^-1 compared to the high-spin to low-spin redox couple [Co(bpy)₃]^3+/2+ at 0.27 M^-1 s^-1, which is attributed to the change in spin state being somewhat offset by this coordination switching behavior. The complexes were utilized as redox shuttles in dye-sensitized solar cells with the near-IR AP25 + D35 dye system and exhibited improved photocurrents over the [Co(bpy)₃]^3+/2+ redox shuttle (19.8 vs 18.0 mA/cm²). Future directions point toward pairing the low-spin to low-spin Co(II/III) tunable series to dyes with significantly more negative highest occupied molecular orbital potentials that absorb into the near-IR where outer sphere redox shuttles have failed to produce efficient dye regeneration.

Crystal structures of (Z)-(ethene-1,2-di-yl)bis-(di-phenyl-phosphine sulfide) and its complex with PtII dichloride

The crystal structures of (Z)-(ethene-1,2-di-yl)bis-(di-phenyl-phosphine sulfide), C₂₆H₂₂P₂S₂ (I), along with its complex with Pt^II dichloride, di-chlorido[(Z)-(ethene-1,2-di-yl)bis-(di-phenyl-phosphine sulfide)-κ² S,S']platinum(II), [PtCl₂(C₂₆H₂₂P₂S₂)] (II), are described here. Compound I features P=S bond lengths of 1.9571 (15) and 1.9529 (15) Å, with a torsion angle of 166.24 (7)° between the two phosphine sulfide groups. The crystal of compound I features both intra-molecular C-H⋯S hydrogen bonds and π-π inter-actions. Mol-ecules of compound I are held together with inter-molecular π-π and C-H⋯π inter-actions to form chains that run parallel to the z-axis. The inter-molecular C-H⋯π inter-action has a H⋯Cg distance of 2.63 Å, a D⋯Cg distance of 3.573 (5) Å and a D-H⋯Cg angle of 171° (where Cg refers to the centroid of one of the phenyl rings). These chains are linked by relatively long C-H⋯S hydrogen bonds with D⋯A distances of 3.367 (4) and 3.394 (4) Å with D-H⋯A angles of 113 and 115°. Compound II features Pt-Cl and Pt-S bond lengths of 2.3226 (19) and 2.2712 (19) Å, with a P=S bond length of 2.012 (3) Å. The Pt^II center adopts a square-planar geometry, with Cl-Pt-Cl and S-Pt-S bond angles of 90.34 (10) and 97.19 (10)°, respectively. Mol-ecules of compound II are linked in the crystal by inter-molecular C-H⋯Cl and C-H⋯S hydrogen bonds.

Highly Selective Nitroamino Isomerization Guided by Proton Transport Dynamics: Full-Nitroamino Imidazole[4,5-d]pyridazine Fused-Ring System

Due to the advantage of the hydrogen bond system formed by nitroamino isomerization, by the calculations of hydrogen transfer in reported nitroamino explosives, the proton transport dynamics was first proposed to predict the nitroamino isomerization of energetic materials. With the calculated results of zero-point energy, the full-nitroamino fused energetic materials, 2,4-nitroamino-7-nitroimino-1,5-dihydro-4H-imidazolo[4,5-d]pyridazine (FNPI-1) and 2,2',7,7'-tetranitromino-4,4'-azo-imidazolo[4,5-d]pyridazine (FNPI-2) were designed and successfully synthesized. The highly selective nitroamino isomerization of neutral compound FNPI-1 is shown by X-ray diffraction. After the hydrogen transfer occurs, the intermolecular hydrogen bonds will greatly promote tight stacking, which enhances the density and thus a series of comprehensive properties of energetic materials. The theoretical calculations of zero-point energy explain perfectly the selectivity of hydrogen transfer between the nitroamino groups and the fused-ring skeleton for FNPI-1. The hydrogen atom transfer and selective isomerization of nitroamino energetic materials can be accurately predicted following proton transport dynamics, which provides computational bases and new ideas for the efficient design of fully nitroamino-based explosives.

Construction of Highly Thermostable and Insensitive Three-Dimensional Energetic Salts Based on [1,2,5]Oxadiazolo[3,4-d]pyrimidine

A novel method for accessing energetic salts of a fused-ring skeleton based on [1,2,5]oxadiazolo[3,4-d]pyrimidine and three alkali metals, sodium (Na), potassium (K), and cesium (Cs), was developed. All three compounds were fully characterized, and their structures were confirmed by single-crystal X-ray analysis. They were highly thermally stable (>290 °C) and had high density, good detonation properties, and insensitive properties, which suggested possible heat-resistant explosive applications.

Energetic Salts of Sensitive N,N'-(3,5-Dinitropyrazine-2,6-diyl)dinitramide Stabilized through Three-Dimensional Intermolecular Interactions

N-nitration of 2,6-diamino-3,5-dinitropyrazine (ANPZ) leads to a sensitive energetic compound N,N'-(3,5-dinitropyrazine-2,6-diyl)dinitramide. This nitro(nitroamino) compound was stabilized by synthesizing energetic salts, dipotassium (3,5-dinitropyrazine-2,6-diyl)bis(nitroamide) (3) and diammonium (3,5-dinitropyrazine-2,6-diyl)bis(nitroamide) (4). Compounds 3 and 4 are fully characterized by single-crystal X-ray diffraction. Compound 3 exhibits a three-dimensional energetic metal-organic framework (3D EMOF) structure and an outstanding overall performance by combining high experimental density (2.10 g cm^-3), good thermal stability (T_d(onset) = 220 °C), and good calculated performance of detonation (D = 8300 m s^-1, P = 29.9 GPa). Compound 4 has acceptable thermal stability (155 °C), moderate experimental density (1.73 g cm^-3), and good calculated performance of detonation (D = 8624 m s^-1, P = 30.8 GPa). The sensitivities of compounds 3 and 4 toward impact and friction were determined following standard methods (BAM). The energetic character of compounds 3 and 4 was determined using red-hot needle and heated plate tests. The results highlight a 3D EMOF (3) based on a six-membered heterocycle as a potential energetic material.

Crystal structure of chlorido[diphenyl(thiophen-2-yl)phosphine-κP]gold(I)

The crystal structure of the title compound, [AuCl(C16H13PS)], is reported. The molecular structure features a nearly linear arrangement of the chloride and phosphino ligands around the gold(I) center, with a P—Au—Cl bond angle of 179.42 (9)°. The Au—P and Au—Cl bond lengths are 2.226 (2) and 2.287 (2) Å, respectively. The geometry of the groups bonded to the phosphorus atom of the ligand is a slightly distorted tetrahedron. The phenyl and thienyl rings of the ligand are extensively disordered, with the thienyl refined over all three possible positions on the phosphorus atom. The relative occupancy ratio between these positions was found to be 0.406 (3):0.406 (2):0.188 (2). One of the major thienyl ring positions with the relative occupancy of 0.406 was modeled as two rotational isomers around the C—P bond with a relative occupancy ratio of 0.278 (3):0.128 (3). Intermolecular C—H...π interactions present in the crystal lattice link molecules of the title compound together to form a complex three-dimensional network.

Synthesis of Ester-Substituted Indolizines from 2-Propargyloxypyridines and 1,3-Dicarbonyls

Two new complementary Au(I)-catalyzed methods for the preparation of ester-substituted indolizines from easily accessible 2-propargyloxypyridines and either acetoacetates or dimethyl malonate are reported. These reactions tolerate a wide range of functionality, allowing for diversification at three distinct positions of the product (R, R¹, R²). For electron-poor substrates, the highest yields are observed upon reaction with acetoacetates, while neutral and electron-rich substrates give higher yields upon treatment with dimethyl malonate.

Synthesis of diphenyl-(2-thienyl)phosphine, its chalcogenide derivatives and a series of novel complexes of lanthanide nitrates and triflates

A novel synthesis of diphenyl(2-thienyl)phosphine, along with its' oxide, sulfide and selenide derivatives, is reported here. These phosphines have been characterized by NMR, IR, MS and X-Ray crystallography. The phosphine oxide derivative was reacted with a selection of lanthanide(III) nitrates and triflates, LnX₃, to give the resultant metal-ligand complexes. These complexes have also been characterized by NMR, IR, MS and X-Ray crystallography. Single crystal X-Ray diffraction data shows a difference in metal-ligand complex stoichiometry and stereochemistry depending on the counteranion (nitrate vs. triflate). The [Ln(Ar₃PO)₃(NO₃)₃] ligand-nitrate complexes are nine-coordinate to the metal in the solid state (bidentate nitrate), featuring a 1 : 3 lanthanide-ligand ratio and bear an overall octahedral arrangement of the six, coordinated ligands. Our [Ln(Ar₃PO)₃(NO₃)₃] ligand-nitrate complexes gave three examples of fac-stereochemistry, where mer-stereochemistry is almost universally observed in the literature of highly related [Ln(Ar₃PO)₃(NO₃)₃] complexes. For the Tb complexes, two different arrangements of the ligands around the metal were observed in the solid state for [Tb(Ar₃PO)₃(NO₃)₃] and [Tb(Ar₃PO)₄(OTf)₂] [OTf]. [Tb(Ar₃PO)₃(NO₃)₃] is strictly nine-coordinate, ligand mer-stereochemistry in the solid state, and [Tb(Ar₃PO)₄(OTf)₂] [OTf] is strictly octahedral, six-coordinate, with a square-planar stereochemical arrangement of the phosphine oxide ligands around the metal.

Effects of nitric acid concentration for nitration of fused [1,2,5]oxadiazolo[3,4-d]pyrimidine-5,7-diamine

Nitration reactions are very often used for the selective synthesis of novel, high performing nitramine-based materials. Now nitration reactions of the fused 5,7-diamino pyrimidine derivative 1, under different nitric acid...

Pushing the Limit of Nitro Groups on a Pyrazole Ring with Energy-Stability Balance

Polynitro compounds exhibit high density and good oxygen balance, which are desirable for energetic material applications, but their syntheses are often very challenging. Now, the design and syntheses of a new three-dimensional (3D) energetic metal-organic framework (EMOF) and high-energy-density materials (HEDMs) with good thermal stabilities and detonation properties based on a polynitro pyrazole are reported. Dipotassium 3,5-bis(dinitromethyl)-4-nitro-1H-pyrazole (5) exhibits a 3D EMOF structure with good thermal stability (202 °C), a high density of 2.15 g cm^-3 at 100 K (2.10 g cm^-3 at 298 K) in combination with superior detonation performance (D_v = 7965 m s^-1, P = 29.3 GPa). Dihydrazinium 3,5-bis(dinitromethyl)-4-nitro-1H-pyrazole (7) exhibits a good density of 1.88 g cm^-3 at 100 K (1.83 g cm^-3 at 298 K) and superior thermal stability (218 °C), owing to the presence of 3D hydrogen-bonding networks. Its detonation velocity (8931 m s^-1) and detonation pressure (35.9 GPa) are considerably superior to those of 1,3,5-trinitro-1,3,5-triazine (RDX). The results highlight the syntheses of a 3D EMOF (5) and HEDM (7) with five nitro groups as potential energetic materials.

Probing Catalyst Function - Electronic Modulation of Chiral Polyborate Anionic Catalysts

Boroxinate complexes of VAPOL and VANOL are a chiral anionic platform that can serve as a versatile staging arena for asymmetric catalysis. The structural underpinning of the platform is a chiral polyborate core that covalently links together alcohols (or phenols) and vaulted biaryl ligands. The polyborate platform is assembled in situ by the substrate of the reaction, and thus a multiplex of chiral catalysts can be rapidly assembled from various alcohols (or phenols) and bis-phenol ligands for screening of catalyst activity. In the present study, variations in the steric and electronic properties of the phenol/alcohol component of the boroxinate catalyst are probed to reveal their effects on the asymmetric induction in the catalytic asymmetric aziridination reaction. A Hammett study is consistent with a mechanism in which the two substrates are hydrogen-bonded to the boroxinate core in the enantiogenic step. The results of the Hammett study are supported by a computational study in which it is found that the H-O distance of the protonated imine hydrogen bonded to the anionic boroxinate core decreases with an increase in the electron releasing ability of the phenol unit incorporated into the boroxinate. The results are not consistent with a mechanism in which the boroxinate catalyst functions as a Lewis acid and activates the imine by a Lewis acid/Lewis base interaction.

Nucleophilic Catalyzed Structural Binary Cleavage of a Fused [5,5]-Bicyclic Compound

Structural binary cleavage of 3,7-diamino-2,6-dinitro-1H,5H-pyrazolo-[1,2-a]pyrazole-1,5-dione 3, under nucleophilic conditions, leads to the formation of a monocyclic pyrazole unit of 5-amino-4-nitro-1,2-dihydro-3H-pyrazol-3-one, 4. Additionally, various salts of the pyrazole ring were synthesized and fully characterized. Detonation properties and mechanical sensitivities of 4 and other new compounds are remarkably improved compared to 3. This simple and efficient strategy is highly desirable for future studies on the development of insensitive and high performing materials.

1,2-Bis(5-(trinitromethyl)-1,2,4-oxadiazol-3-yl)diazene: a water stable, high-performing green oxidizer

Trinitromethane moieties are very important for the design and development of high performing dense green oxidizers. The novel oxidizer 1,2-bis(5-(trinitromethyl)-1,2,4-oxadiazol-3-yl)diazene, 14 is stable in water in contrast to 1,2,4-oxadiazoles with other electron withdrawing substituents at the C5-position. Compound 14 is a CNO-based oxidizer with positive oxygen balance (+6.9%), moderate thermostability, and mechanical insensitivity that may find useful applications in the field of green rocket propallant.

One Step Closer to an Ideal Insensitive Energetic Molecule: 3,5-Diamino-6-hydroxy-2-oxide-4-nitropyrimidone and its Derivatives

Reaching the goal of developing an insensitive high-energy molecule (IHEM) is a major challenge. In this study, 3,5-diamino-6-hydroxy-2-oxide-4-nitropyrimidone (IHEM-1) was synthesized in one step from 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide hydrate (ICM-102 hydrate). The density of compound IHEM-1 is 1.95 g cm^-3 with a decomposition temperature of 271 °C. Its detonation velocity and pressure are 8660 m s^-1 and 33.64 GPa, respectively, which are far superior to the detonation performance of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), while its sensitivity is identical with that of TATB. In addition, four derivatives (1a, chloride; 1b, nitrate; 1c, perchlorate; and 1d, dinitramide) were prepared on the basis of the weak base site (N-O group) and show excellent energetic properties. By combining a series of advantages, including simple preparation, high yield, high density, very low solubility in aqueous solution, high thermostability, insensitivity, and excellent detonation performance, IHEM-1 approaches an ideal insensitive high-energy molecule. Compounds 1b-1d are also competitive as new high-energy-density materials.

Synthesis, identification, density functional and Hirshfeld surface studies of 2,2'-disulfanediylbis(tetrahydro-4H-cyclopenta[d][1,3,2]dioxaphosphole-2-sulfide)

The new compound 2,2'-disulfanediylbis (tetrahydro-4H-cyclo penta[d][1,3,2]dioxaphosphole 2-sulfide), the dimeric form of 2-mercaptotetrahydro-4H-cyclopenta[d] [1,3,2] dioxaphosphole 2-sulfide, has been synthesized and characterized by elemental analysis, molecular weight determination and spectral data (¹ H-NMR, ¹³ C-NMR, ³¹ P-NMR, FTIR). The molecular geometry was confirmed by single X-Ray crystallography. The ground state property was examined by PBE0 and B3LYP density functionals using aug-cc-pV(Q+d)Z basis set in the gas phase and in DMSO solution. The preference of PBE0 functional was statistically established. Thermodynamic parameters and standard heat of dissociation reaction ( Δ H R 298 K o ) have been established. The calculated equilibrium constants at different temperatures reflect the stability of the dimer over the monomers at low temperatures and vice versa. Valency and Fukui indices calculations showed that the monomer is more reactive than the dimer. 2D-fingerprint revealed that, while the H…X; [X = H, O and S] nonbonding intermolecular interactions and reciprocals play a crucial role in strengthening of molecules packing in the crystal unit cell while the S…S ones contribute negatively on it.

Dual anticancer and antibacterial activities of bismuth compounds based on asymmetric [NN'O] ligands

Two new bismuth(III) complexes, [BiL¹Cl₂] (1) and [BiL²Cl₂] (2), in which L¹ is (2-hydroxy-4-6-di-tert-butylbenzyl-2-pyridylmethyl)amine and L² is 2,4-diiodo-6-((pyridine-2-ylmethylamino)methyl)phenol, were synthesized and characterized by elemental and conductivity analyses, atomic absorption spectrometry, infrared and ¹H NMR spectroscopies. The molecular structure of 1 reveals that the NN'O ligand forms a 1:1 complex with bismuth through coordination via the nitrogen of the aliphatic amine, the nitrogen of the pyridine ring and the oxygen of the phenolate. The coordination sphere is completed with two chloride anions in a distorted square pyramidal geometry. Bismuth exhibits the same coordination mode in compound 2. The cytotoxic activity of 1 and 2 was investigated in a chronic myelogenous leukemia cell line. The complexes are approximately three times more potent than the corresponding free ligands, with the IC₅₀ values 0.30 and 0.38 μM for complex 1 and 2, respectively. To address the cellular mechanisms underlying cell demise, apoptosis was quantified by flow cytometry analysis. From 0.1 μM, both complexes induce apoptosis and there is a remarkable concentration-dependent increase in the population of cells in apoptosis. The complexes were also evaluated against Gram-positive and Gram-negative bacteria. Both inhibited the bacterial growth in a concentration-dependent way, with remarkable activity in some of the tested strains, for example, complex 2 was more active than its free ligand against all bacterial strains and approximately fourteen times more potent against S. dysenteriae and S. typhimurium.

Energetic Tricyclic Polynitropyrazole and Its Salts: Proton-Locking Effect of Guanidium Cations

An axisymmetric polynitro-pyrazole molecule, 3,5-di(3,5-dinitropyrazol-4-yl)]-4-nitro-1H-pyrazole (5), and its salts (6-12) were prepared and fully characterized. These compounds not only show promising energetic properties but also show a unique tautomeric switch via combining different cations with the axisymmetric compound (5). Its salts (6-9) remain axisymmetric when the cations are potassium, ammonium, or amino-1,2,4-triazolium. However, when the cations are guanidiums, the salts (10-12) dramatically become asymmetric owing to the fixed proton. The introduction of guanidium cations breaks the tautomeric equilibrium by blocking the prototropic transformations and results in the switch-off effect to tautomerism. The structural constraints of ¹H NMR and ¹³C NMR spectra provide strong evidence for the unusual structural constraint phenomenon. These stabilized asymmetric tautomers are very important from the point of molecular recognition, and this research may promote further developments in synthetic and isolation methodologies for novel bioactive pyrazole-based compounds.

Selective Synthesis of Bis(3-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)-4,4'-azo- and -azoxyfurazan Derivatives

In this paper, we report the synthesis of two new derivatives, bis(3-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)-4,4'-azo- and -azoxyfurazans by selective oxidation of 4-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)-1,2,5-oxadiazol-3-amine. Ammonium salts of these derivatives were prepared, and all of them were fully characterized by multinuclear NMR, FTIR spectroscopy, elemental analysis, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. All of the new compounds have high measured crystal densities, and the energetic properties have been investigated.

Crystal structure of tris-(2-di-cyclo-hexyl-phosphino-2',6'-dimeth-oxy-1,1'-biphenyl-κP)-μ-oxoethenyl-idene-triangulo-trigold(I) bis-(tri-fluoro-methane-sulfon-yl)imide

The title ketenyl-idene, [Au3(C2O)(C26H35O2P)3](C2F6NO4S2), was obtained upon exposure of [2-(di-cyclo-hexyl-phosphino)-2',6'-dimeth-oxy-1,1'-biphen-yl]gold(I) bis-(tri-fluoro-methane-sulfon-yl)imide to acetic anhydride at elevated temperature. The ketenyl-idene bridge caps the tri-gold cluster. The title compound has provided crystals that upon analysis represent the first tri-gold ketenyl-idene with atomic distances indicative of bonding inter-action between the gold atoms.

Very thermostable energetic materials based on a fused-triazole: 3,6-diamino-1H-[1,2,4]triazolo[4,3-b][1,2,4]triazole

The fused-triazole backbone 1H-[1,2,4]triazolo[4,3-b][1,2,4]triazole with two C-amino groups gave a highly thermally energetic compound.

HFOX-1-Amino-1-hydrazino-2,2-Dinitroethylene as a Precursor to Trifluoromethyl, Dinitro, or Trinitro-Based Energetic 1,2,4-Triazoles

The chemical reactivity of 1-amino-1-hydrazino-2,2-dinitroethylene with a carboxylic acid for the construction of structurally interesting energetic triazoles and their energetic salts is reported. All new compounds were fully characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. Crystal analysis, good detonation properties, and low sensitivities of these trifluoromethyl and dinitro- or trinitro-based triazoles suggest their role as potential candidates for insensitive high-energy-density materials.

Hydrogen bond system generated by nitroamino rearrangement: new character for designing next generation energetic materials

Hydrogen bond systems stabilize molecules and shorten intermolecular distances to give higher density and lower sensitivity.

Mono-N-oxidation of heterocycle-fused pyrimidines

Mild oxidation reactions of nitrogen-rich heterocyclic rings lead to the formation of energetic compounds with the mono-N-oxide moiety which show good thermal stabilities and detonation performances.

Ritter-enabled catalytic asymmetric chloroamidation of olefins

Intermolecular asymmetric haloamination reactions are challenging due to the inherently high halenium affinity (HalA) of the nitrogen atom, which often leads to N-halogenated products as a kinetic trap. To circumvent this issue, acetonitrile, possessing a low HalA, was used as the nucleophile in the catalytic asymmetric Ritter-type chloroamidation of allyl-amides. This method is compatible with Z and E alkenes with both alkyl and aromatic substitution. Mild acidic workup reveals the 1,2-chloroamide products with enantiomeric excess greater than 95% for many examples. We also report the successful use of the sulfonamide chlorenium reagent dichloramine-T in this chlorenium-initiated catalytic asymmetric Ritter-type reaction. Facile modifications lead to chiral imidazoline, guanidine, and orthogonally protected 1,2,3 chiral tri-amines.

Intermolecular haloamination reactions are challenging due to the high halenium affinity of the nitrogen atom. This is circumvented by using acetonitrile as an attenuated nucleophile, resulting in an enantioselective halo-Ritter reaction.

Syntheses and crystal structures of the anhydride 4-oxa-tetra-cyclo-[5.3.2.02,6.08,10]dodec-11-ene-3,5-dione and the related imide 4-(4-bromo-phen-yl)-4-aza-tetra-cyclo-[5.3.2.02,6.08,10]dodec-11-ene-3,5-dione

The Diels–Alder cyclo­addition of cyclo­hepta­triene and maleic anhydride produces the title carb­oxy­lic anhydride; reaction of this anhydride with 4-bromo­phenyl­aniline forms the corresponding tetra­cyclic imide. The anhydride features C—H⋯O hydrogen bonds in the solid state, while the imide also features C—H⋯O hydrogen bonds as well as C—H⋯π and lone pair–π inter­actions.

The syntheses and crystal structures of the two title compounds, C₁₁H₁₀O₃ (I) and C₁₇H₁₄BrNO₂ (II), both containing the bi­cyclo­[2.2.2]octene ring system, are reported here [the structure of I has been reported previously: White & Goh (2014 ▸). Private Communication (refcode HOKRIK). CCDC, Cambridge, England]. The bond lengths and angles of the bi­cyclo­[2.2.2]octene ring system are similar for both structures. The imide functional group of II features carbonyl C=O bond lengths of 1.209 (2) and 1.210 (2) Å, with C—N bond lengths of 1.393 (2) and 1.397 (2) Å. The five-membered imide ring is nearly planar, and it is positioned exo relative to the alkene bridgehead carbon atoms of the bi­cyclo­[2.2.2]octene ring system. Non-covalent inter­actions present in the crystal structure of II include a number of C—H⋯O inter­actions. The extended structure of II also features C—H⋯O hydrogen bonds as well as C—H⋯π and lone pair–π inter­actions, which combine together to create supra­molecular sheets.