High‐Nitrogen‐Based Pyrotechnics: Perchlorate‐Free Red‐ and Green‐Light Illuminants Based on 5‐Aminotetrazole

Prototype testing of perchlorate‐free hand‐held signal illuminants for the US Army’s M126 A1 red‐star and M195 green‐star parachute illuminants are described. Although previous perchlorate‐free variants for these items have been developed based on high‐nitrogen compounds that are not readily available, the new formulations consist of anhydrous 5‐aminotetrazole as the suitable perchlorate replacement. Compared to the perchlorate‐containing control, the disclosed illuminants exhibited excellent stabilities toward various ignition stimuli and had excellent pyrotechnic performance. The illuminants are important from both military and civil fireworks perspectives, as the perchlorate‐free nature of the illuminants adequately address environmental concerns associated with perchlorate‐containing red‐ and green‐light‐emitting illuminants.     

Brighter‐ and Longer‐Burning Barium‐Free Illuminants for Military and Civilian Pyrotechnics

The development of barium‐free pyrotechnic illuminants is described. Heavy metal barium nitrate oxidizer and strontium nitrate oxidizer were replaced with sodium nitrate to adequately address environmental concerns while providing the brightest possible illuminant. The new formulations further address environmental concerns and mitigate single‐point‐of‐failure through the replacement of polyester‐based Laminac 4116/Lupersol binder system with the epoxy‐based Epon 813/Versamid 140 binder system. The new formulations were found to burn longer and brighter than the control with a low sensitivity to various ignition stimuli.     

High‐Performing Red‐Light‐Emitting Pyrotechnic Illuminants through the Use of Perchlorate‐Free Materials

The development of perchlorate‐free M662 40 mm illuminating pyrotechnic compositions is described. On the bases of cost, performance, and sensitivity, potassium periodate was determined to be most effective potassium perchlorate replacement in the compositions tested. The optimal periodate‐based composition exceeded the performance of the perchlorate‐containing control, exhibited low sensitivity values to impact, friction, and electrostatic discharge, and had high thermal onset temperatures.     

High-nitrogen-based pyrotechnics: longer- and brighter-burning, perchlorate-free, red-light illuminants for military and civilian applications

The full-up prototype testing of perchlorate-free, hand-held, signal illuminants for the US Army's M126A1 red star parachute hand-held signal is described. Compared to the perchlorate-containing control, the disclosed illuminants yielded excellent stabilities toward various ignition stimuli while offering superior pyrotechnic performance. Militarily, the illuminants provided further evidence that development of smaller hand-held signal items in an environmentally conscious way is a realistic and obtainable goal. The results are also important from the perspective of civilian fireworks, as the development of brighter, longer-burning, and environmentally compatible red-light-emitting pyrotechnics is now possible.     

Perchlorate‐Free Pyrotechnic Formulations Utilizing Energetic Chlorine Donors: 1‐CDN, 11‐CDN, 13‐CDN

Several novel materials were investigated as energetic chlorine donors, specifically for the preparation of perchlorate‐free pyrotechnic formulations with low‐smoke output. The novel compounds, 2‐chloromethyl‐2‐methyl‐5,5‐dinitro‐1,3‐dioxane (1‐CDN), 2,2‐bis(chloromethyl)‐5,5‐dinitro‐1,3‐dioxane (13‐CDN), and 2‐(dichloromethyl)‐2‐methyl‐5,5‐dinitro‐1,3‐dioxane (11‐CDN), were formulated with a variety of fuels and oxidizers and their resulting colored flames analyzed for color quality. The preparation and preliminary characterization of these energetic chlorine donors are described.     

A Strontium‐ and Chlorine‐Free Pyrotechnic Illuminant of High Color Purity

The development of a red‐light‐emitting pyrotechnic illuminant has garnered interest from the pyrotechnics community owing to potential regulations by the United States Environmental Protection Agency (U.S. EPA) regarding the use of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium‐based red‐light‐emitting pyrotechnic compositions of high purity and color quality is described. These formulations do not contain strontium or chlorinated organic materials. Rather, the disclosed formulations are based on a non‐hygroscopic dilithium nitrogen‐rich salt that serves as both oxidizer and red colorant. These formulations are likely to draw interest from the civilian fireworks and military pyrotechnics communities for further development as they both have a vested interest in the development of environmentally conscious formulations.     

7Li NMR chemical shift titration and theoretical DFT calculation studies: solvent and anion effects on second‐order complexation of 12‐crown‐4 and 1‐aza‐12‐crown‐4 with Lithium cation in several aprotic solvents

⁷Li NMR titration was used to determine stepwise complexation constants for the second‐order complexation of lithium cation with 12‐crown‐4 in acetonitrile, propylene carbonate and a binary mixture of propylene carbonate and dimethyl carbonate. The anions used were perchlorate, hexaflurophosphate and trifluromethanesulfonate. A second ligand 1‐aza‐12‐crown‐4 was similarly investigated. The exchange between the free and complexed cation in these reactions is fast on an NMR timescale resulting in a single lithium peak which is a concentration‐weighted average of the free and bound species. Solvent effects show that the 1:1 complex is much more stable in acetonitrile than in propylene carbonate or in the propylene carbonate dimethyl carbonate mixture. Anion effects for a given solvent were small. Optimized geometries of the free ligands and the 1:1 and 1:2 (sandwich) metal–ligand complexes were predicted by hybrid‐density functional theory using the Gaussian 03 software package. Results were compared to literature values for 1:1 stability constants found by microcalorimetry for several of these systems and are found to be in good agreement. Although microcalorimetry only considered the formation of 1:1 complexes, ⁷Li NMR shows evidence that both 1:1 and 1:2 complexes should be considered. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of 1‐Ethyl‐5H‐tetrazole and 1‐Azidoethyl‐5H‐tetrazole as Ligands in Energetic Transition Metal Complexes

Energetic coordination compounds (ECC) based on 3d or 4d transition metals show promising characteristics to be used as potential replacements for highly toxic lead‐containing primary explosives. Herein we report the synthesis of 12 new ECC based on 1‐azidoethyl‐5H‐tetrazole (AET) or 1‐ethyl‐5H‐tetrazole (1‐ETZ) as nitrogen‐rich ligands as well as various central metals (Cu²⁺, Fe²⁺, Zn²⁺, Ag⁺) and anions such as perchlorate and nitrate. The influence of the increased endothermicity by adding an additional azide group was studied by comparing analogous ECC based on AET and 1‐ETZ. Furthermore, the compounds were extensively analyzed by XRD, IR, EA, solid‐state UV/Vis, and DTA as well as their sensitivities toward impact and friction were determined with BAM standard techniques, together with their sensitivity against electrostatic discharge. The sensitivities were compared with the one toward ball drop impact measurements. Classical initiation tests (nitropenta filled detonators) and ignition by laser irradiation highly prove the potential use of the most promising compounds in lead‐free initiation systems.     

3,4‐Di‐2‐pyridyl‐1,2,5‐oxadiazole and its perchlorate salt

In 3,4‐di‐2‐pyridyl‐1,2,5‐oxadiazole (dpo), C₁₂H₈N₄O, each mol­ecule resides on a twofold axis and inter­acts with eight neighbours via four C—H⋯N and four C—H⋯O inter­actions to generate a three‐dimensional hydrogen‐bonded architecture. In the perchlorate analogue, 2‐[3‐(2‐pyrid­yl)‐1,2,5‐oxadiazol‐4‐yl]pyridinium perchlorate, C₁₂H₉N₄O⁺·ClO₄⁻ or [Hdpo]ClO₄, the [Hdpo]⁺ cation is bisected by a crystallographic mirror plane, and the additional H atom in the cation is shared by the two pyridyl N atoms to form a symmetrical intra­molecular N⋯H⋯N hydrogen bond. The cations and perchlorate anions are linked through C—H⋯O hydrogen bonds and π–π stacking inter­actions to form one‐dimensional tubes along the b‐axis direction.     

2‐[6‐(1H‐Benzimidazol‐2‐yl)‐2‐pyridyl]‐1H‐benzimidazol‐3‐ium perchlorate monohydrate

The title compound, C₁₉H₁₄N₅⁺·ClO₄^?·H₂O, contains planar C₁₉H₁₄N₅⁺ cations, perchlorate anions and water mol­ecules. The two closest parallel cations (plane‐to‐plane distance of 3.41 Å), together with two neighbouring perchlorate anions and two water mol­ecules, form an electrically neutral quasi‐dimeric unit. Two acidic H atoms of the cation, both H atoms of the water mol­ecule, the N atoms of the imidazole rings and three of the four O atoms of the perchlorate anion are involved in the hydrogen‐bonding network within the dimeric unit. The remaining third acidic H atom of the imidazole rings and the water mol­ecules complete a two‐dimensional network of hydrogen bonds, thus forming puckered layers of dimers. The angle between the planes of two neighbouring dimeric units in the same layer is 33.25 (3)°.     

Synthesis and Characterization of 3,5‐Diamino‐1,2,4‐triazolium Dinitramide

3,5‐Diamino‐1,2,4‐triazole ( 1 , guanozol) was protonated with diluted hydrochloric acid, nitric acid, as well as perchloric acid forming 3,5‐diamino‐1,2,4‐triazolium chloride hemihydrate ( 2 ), 3,5‐diamino‐1,2,4‐triazolium nitrate ( 3 ) and 3,5‐diamino‐1,2,4‐triazolium perchlorate ( 4 ), respectively. In a second step 4 reacted with potassium dinitramide forming 3,5‐diamino‐1,2,4‐triazolium dinitramide ( 5 ) and low soluble potassium perchlorate. Compounds 2 – 5 were characterized by low temperature single X‐ray diffraction, IR and Raman as well as multinuclear NMR spectroscopy, mass spectrometry and differential scanning calorimetry. The heats of formation of 1 – 5 were calculated by the CBS‐4M method to be 81.1 ( 1 ), 124.7 ( 2 ), –76.1 ( 3 ), –25.2 ( 4 ) and 138.7 ( 5 ) kJ·mol^–1. With these values as well as the X‐ray densities several detonation parameters were calculated using both computer codes EXPLO5.03 and EXPLO5.04. In addition, the sensitivities of 1 – 5 were determined by the BAM drophammer and friction tester as well as a small scale electrical discharge device.     

Theoretical Study of Energetic Complexes (III): Bis‐(5‐nitro‐2H‐tetrazolato‐N2)tetraammine Cobalt(III) Perchlorate (BNCP) and Its Transition Metal (Ni/Fe/Cu/Zn) Perchlorate Analogues

The geometric conformation and electronic structure of bis‐(5‐nitro‐2H‐tetrazolato‐N²)tetraammine cobalt(III) perchlorate and its Ni/Fe/Cu/Zn analogues are studied under the TPSS (Tao‐Perdew‐Staroverov‐Scuseria) levels of density functional theory in order to throw light on the relationship between their energy gaps and impact sensitivity. While the perchlorate ions are coordinated with the copper cation, which is different from the other four compounds. NBO (Natural bond orbital) analyses indicated that the metal‐ligand interaction in the Co complex is covalent, while the others are ionic. The analysis of the electrostatic potential demonstrated that the O atoms from the nitro‐tetrazole ring and perchlorate were primarily negative, while the other atoms were positive. The study was also conducted to gain a better understanding of the correlation of the energy gap and impact sensitivity.     

Energetic Salts Based on an Oxygen‐Containing Cation: 2,4‐Diamino‐1,3,5‐triazine‐6‐one

A family of energetic salts with high thermal stability and low impact sensitivity based on an oxygen‐containing cation, 2,4‐diamino‐1,3,5‐triazine‐6‐one, were synthesized and fully characterized by IR and multinuclear (¹H, ¹³C) NMR spectroscopy, elemental analysis, and differential scanning calorimetry. Insights into their sensitivities towards impact, friction, and electrostatics were gained by submitting the materials to standard tests. The structures of 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate, 2,4‐diamino‐1,3,5‐triazine‐6‐one sulfate, 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, 2,4‐diamino‐1,3,5‐triazine‐6‐one 5‐nitrotetrazolate were determined by single‐crystal X‐ray diffraction; their densities are 1.691, 1.776, 1.854, and 1.636 g cm^?3, respectively. Most of the salts decompose at temperatures over 180 °C; in particular, the salts 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate and 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, which decompose at 303.3 and 336.4 °C, respectively, are fairly stable. Furthermore, most of the salts exhibit excellent impact sensitivities (>40 J), friction sensitivities (>360 N), and are insensitive to electrostatics. The measured densities of these energetic salts range from 1.64 to 2.01 g cm^?3. The detonation pressure values calculated for these salts range from 14.6 to 29.2 GPa, and the detonation velocities range from 6536 to 8275 m s^?1; these values make the salts potential candidates for thermally stable and insensitive energetic materials.     

Ionic Liquid‐Based Routes to Conversion or Reuse of Recycled Ammonium Perchlorate

New, potentially green, and efficient synthetic routes for the remediation and/or re‐use of perchlorate‐based energetic materials have been developed. Four simple organic imidazolium‐ and phosphonium‐based perchlorate salts/ionic liquids have been synthesized by simple, inexpensive, and nonhazardous methods, using ammonium perchlorate as the perchlorate source. By appropriate choice of the cation, perchlorate can be incorporated into an ionic liquid which serves as its own electrolyte for the electrochemical reduction of the perchlorate anion, allowing for the regeneration of the chloride‐based parent ionic liquid. The electrochemical degradation of the hazardous perchlorate ion and its conversion to harmless chloride during electrolysis was studied using IR and ³⁵Cl NMR spectroscopies.     

Four NiII complexes with the new cyclam–methylimidazole ligand 1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane

Although it has not proved possible to crystallize the newly prepared cyclam–methylimidazole ligand 1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane (L^Im1), the trans and cis isomers of an Ni^II complex, namely trans‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) monohydrate, [Ni(C₁₅H₃₀N₆)(H₂O)](ClO₄)₂·H₂O, (1), and cis‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate), [Ni(C₁₅H₃₀N₆)(H₂O)](ClO₄)₂, (2), have been prepared and structurally characterized. At different stages of the crystallization and thermal treatment from which (1) and (2) were obtained, a further two compounds were isolated in crystalline form and their structures also analysed, namely trans‐{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}(perchlorato)nickel(II) perchlorate, [Ni(ClO₄)(C₁₅H₃₀N₆)]ClO₄, (3), and cis‐{1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) 0.24‐hydrate, [Ni(C₂₀H₃₆N₆)](ClO₄)₂·0.24H₂O, (4); the 1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane ligand is a minor side product, probably formed in trace amounts in the synthesis of L^Im1. The configurations of the cyclam macrocycles in the complexes have been analysed and the structures are compared with analogues from the literature.     

Total Synthesis of (−)‐Platensimycin by Advancing Oxocarbenium‐ and Iminium‐Mediated Catalytic Methods

(?)‐Platensimycin is a potent inhibitor of fatty acid synthase that holds promise in the treatment of metabolic disorders (e.g., diabetes and “fatty liver”) and pathogenic infections (e.g., those caused by drug‐resistant bacteria). Herein, we describe its total synthesis through a four‐step preparation of the aromatic amine fragment and an improved stereocontrolled assembly of the ketolide fragment, (?)‐platensic acid. Key synthetic advances include 1) a modified Lieben haloform reaction to directly convert an aryl methyl ketone into its methyl ester within 30 seconds, 2) an experimentally improved dialkylation protocol to form platensic acid, 3) a sterically controlled chemo‐ and diastereoselective organocatalytic conjugate reduction of a spiro‐cyclized cyclohexadienone by using the trifluoroacetic acid salt of α‐amino di‐tert‐butyl malonate, 4) a tetrabutylammonium fluoride promoted spiro‐alkylative para dearomatization of a free phenol to assemble the cagelike ketolide core with the moderate leaving‐group ability of an early tosylate intermediate, and 5) a bismuth(III)‐catalyzed Friedel–Crafts cyclization of a free lactol, with LiClO₄ as an additive to liberate a more active oxocarbenium perchlorate species and suppress the Lewis basicity of the sulfonyloxy group. The longest linear sequence is 21 steps with an overall yield of 3.8 % from commercially available eugenol.     

l‐Leucinium perchlorate

Crystals of l ‐leucinium perchlorate, C₆H₁₄NO₂⁺·ClO₄⁻, are built up from protonated l ‐leucinium cations and perchlorate anions. l ‐Leucinium cations related by a twofold screw axis are inter­connected by N—H⋯O hydrogen bonds into zigzag chains parallel to [010]. The O atoms of the perchlorate anions act as acceptors of hydrogen bonds that link the l ‐leucinium chains into separated but inter­acting two‐dimensional layers parallel to (001). Since the title compound crystallizes in a non‐centrosymmetric space group, it can be useful as a material for non‐linear optics. The efficiency of second harmonic generation is about twice that of K₂[HPO₄].     

(4‐Bromo‐2‐formyl­phenolato)­perchlorato­(1,10‐phenanthroline)­copper(II)

In the title copper(II) compound, [Cu(C₇H₄BrO₂)(ClO₄)(C₁₂H₈N₂)], the Cu atom is five‐coordinated in a distorted square‐pyramidal geometry by the N‐ and O‐donors of 4‐bromo‐2‐formyl­phenolate, 1,10‐phenanthroline and perchlorate. Pairs of complexes are linked together by Cu⋯O(phenolate) and π–π stacking inter­actions between 4‐bromo‐2‐formyl­phenolate and 1,10‐phenanthroline. Along the crystallographic a axis, the dimers are linked by hydrogen bonds between a perchlorate O atom and a 4‐bromo‐2‐formyl­phenolate H atom, and by further π–π stacking inter­actions. Hydrogen bonding between the Br atom and a 1,10‐phenanthroline H atom takes place between the stacks of dimers.     

Synthesis,structural characterization,EPR spectroscopy and Hirshfeld surface analysis of a novel Cu2+‐doped 3,14‐diethyl‐2,13‐diaza‐6,17‐diazoniatricyclo[16.4.0.07,12]docosane bis(perchlorate)

Cyclam derivatives and their metal complexes have been found to exhibit an anti‐HIV effect and stimulate the activity of stem cells from bone marrow. The strength of their binding to the CXCR4 receptor correlates with anti‐HIV and stem‐cell activities. Knowledge of the conformation and crystal packing of various macrocyclic metal complexes has become important in developing new effective anti‐HIV drugs. The synthesis and preparation of single crystals of a new Cu²⁺‐doped macrocyclic compound, (3,14‐diethyl‐2,6,13,17‐tetraazatricyclo[16.4.0.0^7,12]docosane)copper(II) bis(perchlorate)–3,14‐diethyl‐2,13‐diaza‐6,17‐diazoniatricyclo[16.4.0.0^7,12]docosane bis(perchlorate) (0.69/0.31), {[Cu(C₂₂H₄₄N₄)](ClO₄)₂}_0.69·(C₂₂H₄₆N₄²⁺·2ClO₄^?)_0.31, is reported. Characterization by X‐ray diffraction analysis shows that the asymmetric unit contains half of a centrosymmetric molecule. The macrocyclic ligand in the compound adopts the most stable trans‐III conformation. The Cu—N distances of 2.015 (3) and 2.047 (3) Å are normal, but the long axial Cu—O bond of 2.795 (3) Å may be due to a combination of the Jahn–Teller effect and the strong in‐plane ligand field. The crystal structure is stabilized by hydrogen bonding between secondary N—H groups, the N atoms of the macrocycle and the O atoms of the perchlorate anions. Hirshfeld surface analysis with 2D (two‐dimensional) fingerprint plots indicates that the main contributions to the crystal packing are from H…H (58.0%) and H…O/O…H (41.9%) interactions. Electron paramagnetic resonance (EPR) properties are also described.     

Synthesis,Crystal Structure and Spectroscopic Properties of Bis(1‐(E)‐2‐formylpyridine semicarbazone)nickel(II) Diperchlorate Monohydrate

Pale‐green crystals of the title complex were prepared by reaction of 2‐formylpyridine semicarbazone (HCSpy) and nickel(II) perchlorate in boiling ethanol. The crystals are triclinic with the nickel ion in an octahedral arrangement, coordinated by two nitrogen atoms and one oxygen donor atom from each ligand molecule. The effect of coordination on bond lengths and angles was explored by comparison with the single‐crystal structure data of the free ligand HSCpy, which was collected as well. The assumed coordination mode was supported by ¹H and ¹³C NMR spectroscopic data. A detailed analysis of the electronic properties, including semi‐empirical quantummechanical calculations is presented. Furthermore, the data obtained from magnetic susceptibility and EPR measurements are in accordance with a low‐spin d⁸ nickel(II) complex.