Low‐pressure barrier discharge ion source using air as a carrier gas and its application to the analysis of drugs and explosives

In this work, a low‐pressure air dielectric‐barrier discharge (DBD) ion source using a capillary with the inner diameter of 0.115 and 12 mm long applicable to miniaturized mass spectrometers was developed. The analytes, trinitrotoluene (TNT), 1,3,5‐trinitroperhydro‐1,3,5‐triazine (RDX), 1,3,5,7‐tetranitroperhydro‐1,3,5,7‐tetrazocine (HMX), pentaerythritol tetranitrate (PETN), nitroglycerine (NG), hexamethylene triperoxide diamine (HMTD), caffeine, cocaine and morphine, introduced through the capillary, were ionized by a low‐pressure air DBD. The ion source pressures were changed by using various sizes of the ion sampling orifice. The signal intensities of those analytes showed marked pressure dependence. TNT was detected with higher sensitivity at lower pressure but vice versa for other analytes. For all analytes, a marked signal enhancement was observed when a grounded cylindrical mesh electrode was installed in the DBD ion source. Among nine analytes, RDX, HMX, NG and PETN could be detected as cluster ions [analyte + NO₃]^? even at low pressure and high temperature up to 180 °C. The detection indicates that these cluster ions are stable enough to survive under present experimental conditions. The unexpectedly high stabilities of these cluster ions were verified by density functional theory calculation. Copyright © 2016 John Wiley & Sons, Ltd.     

Mass spectral fragmentation pathways in RDX and HMX. A mass analyzed ion kinetic energy spectrometric/collisional induced dissociation study

A collisional induced dissociation study of 1,3,5-trinitro-1,3,5 triazacyclohexane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) was carried out using mass analyzed kinetic energy spectrometry. High resolution mass spectra and mass analyzed ion kinetic energy/collisional induced dissociation spectra of RDX and HMX were recorded in the electron impact, chemical ionization and negative ion chemical ionization modes. Fragmentation pathways of the compounds investigated were determined in all three modes of ionization. It was found that a major part of the fragment ions in RDX and HMX originate from formation of the aduct ions [M+NO]⁺ and [M+NO₂]⁺ in electron impact and chemical ionization, and from [M+NO]^? and [M+NO₂]^? in negative chemical ionization, followed by dissociation.     

The very far-infrared spectra of energetic materials and possible confusion materials using terahertz pulsed spectroscopy

We have measured the terahertz absorption spectra of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), pentaerythritol tetranitrate (PETN), 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX), 2,4,6-trinitrotoluene (TNT), the plastic explosives Semtex H, SX2, and Metabel, and a number of confusion materials using terahertz pulsed transmission spectroscopy. Spectral fingerprints were obtained from 3 to 133 cm⁻¹. The spectra of the plastic explosives are dominated by the spectral signatures of their explosive components due to low frequency vibrations and crystalline phonon modes. Importantly, the terahertz spectra of the confusion materials show no resemblance to the explosives spectra. The refractive indices obtained for the plastic explosives and confusion materials allowed us to derive reflectance spectra, which appear distinct and so suggest that terahertz reflection spectroscopy is a suitable tool for the detection of concealed explosives in security applications.     

A LC-MS method allowing the analysis of HMX and RDX present at the picogram level in natural aqueous samples without a concentration step

The introduction of chloroform into the nebulising gas of a LC/MS electrospray interface (ESI), in a perfectly controlled way, leads to the formation of intense adducts ([M+Cl]⁻) when a mobile phase containing HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane or octogen) and RDX (1,3,5-trintro-1,3,5-triazacyclohexane or hexogen) is eluted. This LC/MS method allows the direct analysis of aqueous samples containing HMX and RDX at the pictogram level without a concentration step. The method is used to determine HMX and RDX concentrations in ground water samples from a military site.     

New theoretically predicted RDX‐ and β‐HMX‐based high‐energy‐density molecules

Theoretically new high‐energy‐density materials (HEDM) in which the hydrogens on RDX and β‐HMX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine and octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine, respectively) were sequentially replaced by (N NO₂)x functional groups were designed and evaluated using density functional theory calculations in combination with the Kamlet–Jacobs equations and an atoms‐in‐molecules (AIM) analysis. Improved detonation properties and reduced sensitivity compared to RDX and β‐HMX were predicted. Interestingly, the RDX and β‐HMX derivatives having one attached N NO₂ group [RDX‐(NNO₂)1 and HMX‐(NNO₂)1] showed excellent detonation properties (detonation velocities: 9.529 and 9.575 km·s⁻¹, and detonation pressures: 40.818 and 41.570 GPa, respectively), which were superior to the parent compounds. Sensitivity estimations obtained by calculating impact sensitivities and HOMO‐LUMO gaps indicated that RDX‐(NNO₂)1 and HMX‐(NNO₂)1 were less stable than RDX and HMX but more stable than any of the other derivatives. This method of sequential NNO₂ group attachment on conventional HEDMs offers a firm basis for further studies on the design of new explosives. Furthermore, the newly found structures may be promising candidates for better HEDMs.     

A systematic tandem mass spectrometric study of anion attachment for improved detection and acidity evaluation of nitrogen‐rich energetic compounds

The development of rapid, efficient, and reliable detection methods for the characterization of energetic compounds is of high importance to security forces concerned with terrorist threats. With a mass spectrometric approach, characteristic ions can be produced by attaching anions to analyte molecules in the negative ion mode of electrospray ionization mass spectrometry (ESI‐MS). Under optimized conditions, formed anionic adducts can be detected with higher sensitivities as compared with the deprotonated molecules. Fundamental aspects pertaining to the formation of anionic adducts of 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane (HMX), 1,3,5‐trinitro‐1,3,5‐triazinane (RDX), pentaerythritol tetranitrate (PETN), nitroglycerin (NG), and 1,3,5‐trinitroso‐1,3,5‐triazinane energetic (R‐salt) compounds using various anions have been systematically studied by ESI‐MS and ESI tandem mass spectrometry (collision‐induced dissociation) experiments. Bracketing method results show that the gas‐phase acidities of PETN, RDX, and HMX fall between those of HF and acetic acid. Moreover, PETN and RDX are each less acidic than HMX in the gas phase. Nitroglycerin was found to be the most acidic among the nitrogen‐rich explosives studied. The ensemble of bracketing results allows the construction of the following ranking of gas‐phase acidities: PETN (1530‐1458 kJ/mol) > RDX (approximately 1458 kJ/mol) > HMX (approximately 1433 kJ/mol) > nitroglycerin (1427‐1327.8 kJ/mol).     

Thermal Analysis of Binary Systems. Explosive – lead compound

The thermal decomposition of explosives: pentaerythrol tetranitrate (PETN), 2,4,6-trinitrotoluene(TNT), cyclo-1,3,5-trimethylene-2,4,6-trinitroamine (RDX) and their two-component mixtures with 40% of lead compounds [PbO, Pb₃O₄, Pb(NO₃)₂] were performed. The simple method of determination of stability changes in the mixtures described above, in comparison with pure explosives was presented. The lead oxides accelerated significantly the thermal decomposition of explosives. Pb(NO₃)₂ acts as a catalyst in the mixture containing TNT degradation, but not in a case of PETN and RDX. This revised version was published online in August 2006 with corrections to the Cover Date.     

Detection of explosives and their degradation products in soil environments

Polynitro organic explosives [hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6-trinitrotoluene (TNT)] are typical labile environmental pollutants that can biotransform with soil indigenous microorganisms, photodegrade by sunlight and migrate through subsurface soil to cause groundwater contamination. To be able to determine the type and concentration of explosives and their (bio)transformation products in different soil environments, a comprehensive analytical methodology of sample preparation, separation and detection is thus required. The present paper describes the use of supercritical carbon dioxide (SC-CO2), acetonitrile (MeCN) (US Environmental Protection Agency Method 8330) and solid-phase microextraction (SPME) for the extraction of explosives and their degradation products from various water, soil and plant tissue samples for subsequent analysis by either HPLC-UV, capillary electrophoresis (CE-UV) or GC-MS. Contaminated surface and subsurface soil and groundwater were collected from either a TNT manufacturing facility or an anti-tank firing range. Plant tissue samples were taken fromplants grown in anti-tank firing range soil in a greenhouse experiment. All tested soil and groundwater samples from the former TNT manufacturing plant were found to contain TNT and some of its amino reduced and partially denitrated products. Their concentrations as determined by SPME-GC-MS and LC-UV depended on the location of sampling at the site. In the case of plant tissues, SC-CO2 extraction followed by CE-UV analysis showed only the presence of HMX. The concentrations of HMX (<200 mg/kg) as determined by supercritical fluid extraction (SC-CO2)-CE-UV were comparable to those obtained by MeCN extraction, although the latter technique was found to be more efficient at higher concentrations (>300 mg/kg). Modifiers such as MeCN and water enhanced the SC-CO2 extractability of HMX from plant tissues.     

Temperature-dependent far-infrared spectra of single crystals of high explosives using terahertz time-domain spectroscopy

Survey spectra of single-crystal HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and PETN (pentaerythritol tetranitrate) were acquired in the region from 10 to 80 cm(-1) using terahertz time-domain spectroscopy. The spectra were taken at temperatures ranging from 8.4 to 300 K. Generally, the spectra show multiple absorption peaks in the range 50-80 cm(-1), with PETN (110) showing strong absorption features at room temperature. RDX (210) is the most notable in the region 10-40 cm(-1), showing multiple spectral features, while HMX (010) shows a very broad absorption at 47.8 cm(-1) with a fwhm of 37.3 cm(-1). Future plans include polarization-dependent investigations for multiple crystallographic orientations over an increased spectral range and higher-level theoretical calculations.     

Ferrocenyl Ionic Compounds Containing [Fe(CN)6]3– Anions: Synthesis,Characterization, and Catalytic Effects during Combustion

Twenty‐eight novel ferrocenyl ionic compounds, composed of mononuclear 1‐ferrocenylmethylalkyldimethylammoniums, 1‐ferrocenylmethyl‐3‐alkylimidazoliums, or their dinuclear analogs and [Fe(CN)₆]^3– anion, were designed and synthesized to tackle significant volatility and migration tendency of ferrocene‐based burning rate catalysts (BRCs) used currently in the composite solid propellants. The new compounds were characterized by UV/Vis, FT‐IR, and elementary analysis. The crystal structures of compounds 2· 5H₂O and 3· CH₂Cl₂ · 4H₂O verified the successful preparation of the desired ionic compounds. The TG tests at 70 °C for 24 h revealed that the new compounds exhibit lower volatility than catocene. The cyclic‐voltammetry results suggested that new compounds are quasi‐reversible or irreversible redox systems. TheTG/DSC analyses exhibited that the compounds are of highly thermal stability. Their catalytic effects on the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), and 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazacyclooctane (HMX) were investigated. The results showed that most of the compounds exert great effects on the thermal degradation of AP and RDX during combustion. 11 and 2 are comparable to catocene in the thermal decomposition of AP and RDX, respectively, and can therefore be used as alternatives of catocene in a composite solid propellant. Some new compounds are unexpectedly active in promoting the thermal disintegration of HMX.     

Determination of nitroaromatic, nitramine, and nitrate ester explosives in soil by gas chromatography and an electron capture detector

Hazardous waste site characterization, forensic investigations, and land mine detection are scenarios where soils may be collected and analyzed for traces of nitroaromatic, nitramine, and nitrate ester explosives. These thermally labile analytes are traditionally determined by high-performance liquid chromatography (HPLC); however, commercially available deactivated injection port liners and wide-bore capillary columns have made routine analysis by gas chromatography (GC) possible. The electron-withdrawing nitro group common to each of these explosives makes the electron capture detector (ECD) suitable for determination of low concentrations of explosives in soil, water, and air. GC-ECD and HPLC-UV concentration estimates of explosives residues in field-contaminated soils from hazardous waste sites were compared, and correlation (r>0.97) was excellent between the two methods of analysis for each of the compounds most frequently detected: 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4-dinitrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), 1,3,5-trinitrobenzene (TNB), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The analytes were extracted from soils with acetonitrile by 18 h of sonication in a cooled ultrasonic bath. Two soil-to-solvent ratios were evaluated: 2.00 g:10.00 ml and 25.0 g:50.0 ml. GC-ECD method detection limits were similar for the two soil-to-solvent ratios and were about 1 mug kg(-1) for the di- and trinitroaromatics, about 10 mug kg(-1) for the mono-nitroaromatics, 3 mug kg(-1) for RDX, 25 mug kg(-1) for HMX, and between 10 and 40 mug kg(-1) for the nitrate esters (nitroglycerine [NG] and pentaerythritol tetranitrate [PETN]). Spike recovery studies revealed artifacts introduced by the spiking procedure. Recoveries were low in some soils if the amount of soil spiked was large (25.0 g) compared to the volume of spike solution added (1.00 ml). Recoveries were close to 100% when 2.00-g soil samples were spiked with 1.00 ml of solution. Analytes most frequently found in soils collected near buried land mines were the microbial transformation products of TNT (2-amino-4,6-dinitrotoluene [2-Am-DNT] and 4-amino-2,6-dinitrotoluene [4-Am-DNT]), manufacturing impurities of TNT (2,4-DNT, 2,6-DNT, and 1,3-DNB), and TNT. The microbial reduction products of the isomers of DNT and of 1,3-DNB were also detected, but the ECD response to these compounds is poor.     

Density functional theory studies of effects of boron replacement on the structure and property of RDX and HMX

In this study, based on two model nitramine compounds hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5, 7-tetrazocine (HMX), two series of new energetic molecules were designed by replacing carbon atoms in the ring with different amounts of boron atoms, their structures and performances were investigated theoretically by the density functional theory method. The results showed that the boron replacement could affect the molecular shape and electronic structure of RDX and HMX greatly, and then would do harm to the main performance like the heat of formation, density, and sensitivity. However, the compound RDX-B2 is an exception; it was formed by replacing two boron atoms into the system of RDX and has the symmetric boat-like structure. Its oxygen balance (4.9%), density (1.91 g/cm³), detonation velocity (8.85 km/s), and detonation pressure (36.9 GPa) are all higher than RDX. Furthermore, RDX-B2 has shorter and stronger N NO₂ bonds than RDX, making it possesses lower sensitivity (45 cm) and better thermal stability (the bond dissociation energy for the N NO₂ bond is 204.7 kJ/mol) than RDX. Besides, RDX-B1 and HMX-B4 also have good overall performance; these three new molecules may be regarded as a new potential candidate for high energy density compounds.     

Fabric analysis by ambient mass spectrometry for explosives and drugs

Desorption electrospray ionization (DESI) is applied to the rapid, in-situ, direct qualitative and quantitative analysis of mixtures of explosives and drugs from a variety of fabrics, including cotton, silk, denim, polyester, rayon, spandex, leather and their blends. The compounds analyzed were explosives: trinitrohexahydro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN) and the drugs of abuse: heroin, cocaine, and methamphetamine. Limits of detection are in the picogram range. DESI analyses were performed without sample preparation and carried out in the presence of common interfering chemical matrices, such as insect repellant, urine, and topical lotions. Spatial and depth profiling was investigated to examine the depth of penetration and lateral resolution. DESI was also used to examine cotton transfer swabs used for travel security sample collection in the screening process. High throughput quantitative analysis of fabric surfaces for targeted analytes is also reported.     

Note on the use of the vacuum stability test in the study of initiation reactivity of attractive cyclic nitramines in Formex P1 matrix

The zero-order reaction rates (specific rate constants) of isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) were measured by means of the Czech vacuum stability test, STABIL. The PBXs are based on 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole (BCHMX), and ε 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-HNIW, ε-CL-20) with 13 wt% of the Formex P1 type matrix, i.e., a matrix of the explosive with pentaerythritol tetranitrate (PETN) bound by 13 wt% of a mixture of 25 wt% of styrene–butadiene rubber and 75 wt% of an oily material. Dependencies were found between the specific rate constants mentioned and the detonation velocities of PBXs, and consequently between these constants and the impact and electric spark sensitivities of pure explosive fillers, i.e., RDX, HMX, HNIW, BCHMX, and PETN. It is stated that the higher impact or electric spark sensitivity of their pure explosive fillers corresponds to the higher thermal reactivity of the given PBXs.     

Solid phase microextraction-high performance liquid chromatographic determination of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in the presence of sodium dodecyl sulfate surfactant

A simple and sensitive method has been developed using preconcentration technique solid phase microextraction (SPME) and analytical technique HPLC-UV for the determination of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) from the environmental samples. Aqueous solution of anionic surfactant SDS was used for the extraction of both nitramine high explosives, viz., HMX and RDX from soil samples which were subsequently sorbed on SPME fiber. The static desorption was carried out in the desorption chamber of the SPME-HPLC interface in the presence of mobile phase ACN/methanol/water (30:35:35) and the subsequent chromatographic analysis at a flow rate of 0.5 mL/min and detection at 230 nm. For this purpose, a C(18), 5 microm RP analytical column was used as a separation medium in this method. Several parameters relating to SPME, e.g., adsorption/desorption time, concentration of salt, stirring rate, etc., were optimized. The method was linear over the range of 20-400 ng/mL for HMX and RDX standards in the presence of surfactant in aqueous phase, respectively. The correlation coefficient (R(2)) for HMX and RDX are 0.9998 and 0.9982, respectively. With SPME, the detection limits (S/N = 3) in ng/mL are 0.05 and 0.1 for HMX and RDX, respectively in the presence of the SDS surfactant. The developed method has been applied successfully to the analysis of real environmental samples like bore well water, river water, and ground alluvial soil.     

Enhanced extraction of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in the presence of sodium dodecyl sulphate and its application to environmental samples

A method for enhanced extraction of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) from environmental samples is developed with the assistance of sodium dodecyl sulphate (SDS) surfactant. In this study, the concentration of SDS surfactant and other analytical parameters are optimized on a high-performance liquid chromatography-UV system. An isocratic flow of 1.0 mL/min with mobile phase acetonitrile-water; 70:30 (v/v) at 230 nm wavelength on a reverse-phase amide column is used for baseline separation of explosives and making calibration curves. The amount of recovered explosives from spiked soil and water samples are calculated. The limits of detection obtained for HMX and RDX standards are 1.5 and 3.8 ppb (S/N=3), respectively, which are much better than obtained by the Environmental Protection Agency method 8330. The recoveries are found to be enhanced by 1.7 and 1.6-fold with SDS solution as compared to water for HMX and RDX, respectively, from soil samples.     

A fast method for monitoring of organic explosives in soil: a gas temperature gradient approach in LC–APCI/MS/MS

A novel, fast liquid chromatography atmospheric pressure chemical ionization mass spectrometry (LC–APCI–MS/MS) screening method was developed to determine the trace amounts of TNT (trinitrotoluene), RDX (1,3,5-trinitroperhydro-1,3,5-triazine), HMX (cyclotetramethylene-tetranitramine), PETN (pentaerythritoltetranitrate), TETRYL (2,4,6-trinitrophenyl-N-methylnitramine), picric acid (2,4,6 trinitrophenol), 2,6-DNT (2,6-dinitrotoluene), and TMETN (trimethylolethane-trinitrate) which contaminate the soil after explosion. A gradient of 2.00 mM ammonium nitrate aqueous solution-methanol mobile system, C18 column, and atmospheric pressure chemical ionization (APCI) (?) ionization mode was used after a single-step solid–liquid extraction procedure from soil matrix. Phenytoin was used as the internal standard. As an extraordinary application, gas temperature gradient in an APCI ionization was used. Analytes were selectively eluted from the system within 10 min. Average recovery obtained from the soil was between 93.01 and 104.20% at 250.0, 500.0, and 1000.0 ngg^?1 concentration levels. Limit of detection (LOD) and limit of quantification (LOQ) values obtained from the analysis of the soil samples including explosive mix were between 8.9–161.2 and 13.2–241.5 ngg^?1, respectively.     

Mono‐ and Dinuclear Ferrocenyl Ionic Compounds with Polycyano Anions. Characterization,Migration, and Catalytic Effects on Thermal Decomposition of Energetic Compounds

Neutral ferrocene‐based burning rate (BR) catalysts show strong migration trends and volatility during long‐time storage and curing of the composite solid propellants. To reduce these disadvantages thirty‐two ferrocenyl quaternary ammonium compounds, paired with polycyano anions, were synthesized and characterized by ¹H NMR, ¹³C NMR, and UV/Vis spectroscopy, as well as elemental analysis. Additionally, crystal structures of eight compounds were confirmed by single‐crystal X‐ray diffraction. TG and DSC analyses indicated that the compounds containing 1,1,2,3,3‐pentacyanopropenide anions show high thermal stability. Cyclic voltammetry studies suggested that they are quasi‐reversible or irreversible redox systems. Anti‐migration tests verified that the tested compounds show very low migration tendency and some of them exhibit no migration after 30 days aging at 70 °C. Their catalytic efficiency in the thermal decomposition of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), and 1,2,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) were examined by DSC analyses. The results revealed that most of the compounds exhibit distinct effects on the thermal degradation of AP and RDX. Two compounds have good catalytic ability in the thermal decomposition of HMX, representing rare examples of the reported ferrocenyl ionic compounds, which display catalytic property during combustion of HMX.     

Neutral desorption using a sealed enclosure to sample explosives on human skin for rapid detection by EESI-MS

A novel air-tight neutral desorption enclosure has been fabricated to noninvasively sample low picograms of explosives 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine (HMX), triacetone triperoxide (TATP), and nitroglycerin (NG) from human skin using a neutral nitrogen gas beam. Without further sample pretreatment, the explosive mixtures collected from the skin surface were directly transported by a nitrogen carrier gas over a 4-m distance for sensitive detection and rapid identification by extractive electrospray ionization tandem mass spectrometry.     

Ionic Ferrocenyl Coordination Compounds Derived from Imidazole and 1,2,4‐Triazole Ligands and Their Catalytic Effects During Combustion

Alkylferrocene‐based burning‐rate catalysts (BRCs) show conspicuous migration tendency and volatility during prolonged storage and fabrication process of a composite solid propellant. To enhance anti‐migration ability of the BRCs, forty novel ionic coordination compounds, [M(L)₄(H₂O)₂]_mX_n (M = Mn²⁺, Co²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Pb²⁺, Cr³⁺, Bi³⁺, or Cd²⁺; L = ferrocenylmethyl imidazole or ferrocenylmethyl‐1,2,4‐triazole; X = picrate or trinitroresorcinolate), were synthesized and characterized by FT‐IR, UV/Vis, and elementary analysis. Additionally, the crystal structures of six compounds were confirmed by single‐crystal X‐ray diffraction. The TG analyses revealed that the new compounds show high thermal stability. Cyclic voltammetry studies suggested that theyare irreversible redox systems. Their catalytic activities in the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclo‐hexane (RDX) and 1,2,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) were examined by DSC technique. The results indicated that all the new compounds exert great effects on the thermal decomposition of AP and RDX, among them some compounds are more active than catocene. Compound 26 has good catalytic ability in the thermal decomposition of HMX, representing a rare example of the reported ferrocene‐based BRCs which show catalytic activity during combustion of HMX.