Synthesis of Bridged Tetrazoles with Promising Properties and Potential Applications by a One-Step Finkelstein Reaction.

Numerous nitramine bridged compounds which show promising combinations of properties have already been identified in the area of energetic materials. In this work, four new nitrazapropane bridged tetrazoles, as well as four new trinitrazaheptane tetrazoles and three oxapropane bridged tetrazoles were synthesized and fully characterized. These new compounds can all be synthesized by a simple, one-step synthesis using Finkelstein conditions. All of these new energetic materials were characterized using NMR spectroscopy, single crystal X-ray diffraction, vibrational analysis and elemental analysis. The thermal behaviour of these compounds was studied by differential thermal analysis (DTA) and partly by thermogravimetric analysis (TGA). The BAM standard method was used to determine the sensitivities towards impact (IS) and friction (FS). The enthalpies of formation were calculated at the CBS-4M level, and the energetic performances were calculated using the EXPLO5 (V6.06.01) computer code. The properties of the new compounds were compared to each other as well as to the known energetic material RDX. Moreover, the iron(II) and copper(II) perchlorate complexes with 1,3-bis-1,1-tetrazolylnitrazapropane as ligand were prepared and investigated.

Melt Castable Derivatives of Pentaerythritol Tetranitrate.

In the search for high-performance and environmentally friendly energetic materials, the derivatization of known materials is an often-applied concept to fulfill modern-day demands. Surprisingly, the long know pentaerythritol tetranitrate (PETN) has only been derivatized to a limited extent. PETN shows a brought application in energetic materials or pharmaceutics. In this work, the PETN backbone is modified by introducing nitramine, ionic nitramine, amine, ionic amine and tetrazole functionalities. The obtained and structurally similar compounds allow good comparability and insights into functional group effects on sensitivity, thermal behavior and performance. The functionalizations result in melting points in the range of 64 to 126 °C. Some compounds are therefore potential candidates to replace toxic TNT.

The Adjustability of Physicochemical Properties: Comparison of 1-Vinyl-5H-tetrazole and 1-Allyl-5H-tetrazole as Ligands in 3d Metal Energetic Coordination Compounds.

Energetic coordination compounds (ECCs) show promising properties to be used as potential substitutes for highly toxic lead-containing primary explosives. The concept is to combine the three building blocks: (i) ligand, (ii) transition metal, and (iii) anion, acting as (i) fuel, (ii) matrix, and (iii) oxidizer (e.g., ClO4-, NO3-, ClO3-) or energetic component (e.g., DN-, N3-, picrate, styphnate, trinitrophloroglucinate). By variation of the ligands, the complexes' properties can be adjusted toward their desired performance and sensitivities. In the present study, 1-vinyl-5H-tetrazole (1-VTZ, 1) and 1-allyl-5H-tetrazole (1-ATZ, 2) were used as nitrogen-rich endothermic ligands to form 3d metal (Mn2+, Fe2+, Cu2+, Zn2+, Co2+, Ni2+)-based ECCs. The influence of the introduction of an unsaturated C-C bond (1-ETZ vs 1-VTZ and 1-PTZ vs 1-ATZ) on the performance and sensitivity of the complexes is discussed, as is the lengthening of the alkenyl chain (1-VTZ vs 1-ATZ). For further insights, the novel complexes were compared to literature-known complexes based on N1-substituted C2- and C3-derived tetrazole ligands, respectively. The ligand 1-VTZ (1) was prepared by elimination of hydrogen chloride from 1-(2-chloroethyl)-5H-tetrazole in methanolic KOH solution. 1-ATZ (2) was obtained by a heterocyclization reaction of allylamine with triethyl orthoformate and sodium azide in an acetic acid medium. All compounds were intensively characterized with analytical methods such as XRD, IR, EA, DTA, TGA, and sensitivity measurements (IS and FS). The energetic performances were visibly evaluated in fast heating experiments. Furthermore, PETN initiation and laser ignition experiments were carried out for promising ECCs.

Synthesis and Characterization of Azido- and Nitratoalkyl Nitropyrazoles as Potential Melt-Cast Explosives.

Desirable advancements in the field of explosive materials include the development of novel melt-castable compounds with melting points ranging from 80 to 110 °C. This is particularly important due to the limited performance and high toxicity associated with TNT (trinitrotoluene). In this study, a series of innovative melt-castable explosives featuring nitratoalkyl and azidoalkyl functionalities attached to the 3-nitro-, 4-nitro-, 3,4-dinitropyrazole, or 3-azido-4-nitropyrazole scaffold are introduced. These compounds were synthesized using straightforward methods and thoroughly characterized using various analytical techniques, including single-crystal X-ray diffraction, IR spectroscopy, multinuclear nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, elemental analysis, and DTA. Furthermore, the energetic properties such as (theoretical) performance data, sensitivities, and compatibilities of the compounds were evaluated and compared among the different structures.

Synthesis and Characterization of Binary, Highly Endothermic, and Extremely Sensitive 2,2'-Azobis(5-azidotetrazole).

2,2'-Azobis(5-azidotetrazole) (C2N16, 3), a highly energetic nitrogen-rich binary CN compound was obtained in a three-step synthesis through the formation of 5-azidotetrazole (1), subsequent amination using O-tosylhydroxylamine to give 2-amino-5-azidotetrazole (2), and oxidative azo coupling of 2 using tBuOCl as an oxidant in MeCN. A nitrogen:carbon ratio of 8:1, eight nitrogen atoms in a row, and a nitrogen content of over 90% was unknown for a binary heterocyclic compound until now. The successful isolation was confirmed through X-ray diffraction as well as by vibrational and 13C NMR spectroscopy. C2N16 can explode instantly and shows mechanical sensitivities far higher than quantitatively measurable. Nevertheless, it features interesting energetic performances, which were calculated using different quantum-chemical methods.

1-(Azidomethyl)-5H-Tetrazole: A Powerful New Ligand for Highly Energetic Coordination Compounds.

Highly energetic 1-(azidomethyl)-5H-tetrazole (AzMT, 3) has been synthesized and characterized. This completes the series of 1-(azidoalkyl)-5H-tetrazoles represented by 1-(azidoethyl)-5H-tetrazole (AET) and 1-(azidopropyl)-5H-tetrazole (APT). AzMT was thoroughly analyzed by single-crystal X-ray diffraction experiments, elemental analysis, IR spectroscopy and multinuclear (1 H, 13 C, 14 N, 15 N) NMR measurements. Several energetic coordination compounds (ECCs) of 3d metals (Mn, Fe, Cu, Zn) and silver in combination with anions such as (per)chlorate, mono- and dihydroxy-trinitrophenolate were prepared, giving insight into the coordination behavior of AzMT as a ligand. The synthesized ECCs were also analyzed by X-ray diffraction experiments, elemental analysis, and IR spectroscopy. Differential thermal analysis for all compounds was conducted, and the sensitivity towards external stimuli (impact, friction, and ESD) was measured. Due to the high enthalpy of formation of AzMT (+654.5 kJ mol-1 ), some of the resulting coordination compounds are extremely sensitive, yet are able to undergo deflagration-to-detonation transition (DDT) and initiate pentaerythritol tetranitrate (PETN). Therefore, they are to be ranked as primary explosives.

Tuning the Properties of 5-Azido and 5-Nitramino-tetrazoles by Diverse Functionalization - General Concepts for Future Energetic Materials.

5-Azido and 5-nitraminotetrazole backbones are established heterocyclic motifs in the research field of energetic materials synthesis. Despite the high energy content of the compounds, the problem with many derivatives is that their sensitivities are far too high. Functionalization of one of the ring nitrogen atoms is the aim of this study to adjust the sensitivity by inserting nitratoethyl, azidoethyl and methyl groups. In this context, derivatives of 2-(2-azidoethyl)-5-nitraminotetrazoles (2, 2 a-2 d), as well as 1-nitrato and 1-azidoethyl substituted 5-azidotetrazole (7 and 10) and the methylation products of 5-azidotetrazole (5-azido-1-methyl-tetrazole, 11 and 5-azido-2-methyl-tetrazole, 12) were prepared. The obtained nitrogen-rich compounds were extensively characterized through multinuclear NMR spectroscopy and IR spectroscopy. The structural confinement was checked by X-ray diffraction experiments. The pure samples (verified by elemental analysis) were investigated regarding their behavior toward friction, impact (BAM methods) and electrostatic discharge as well as heating (DTA and DSC). For all metal-free compounds the detonation properties were computed with the EXPLO5 code using their density and heat of formation, calculated based on CBS-4 M level of theory.

1-(Nitratomethyl)-5H-tetrazole: A Highly Sensitive Ligand with Improved Oxygen Balance for Laser-Ignitable Coordination Compounds.

For the first time, the highly sensitive 1-(nitratomethyl)-5H-tetrazole (1-NAMT) was synthesized, representing the shortest possible 1-(nitratoalkyl)-5H-tetrazole with a combined nitrogen and oxygen content of 81.4%. Compared to its related ethyl derivative, 1-(nitratoethyl)-5H-tetrazole, it exhibits improved oxygen balance, resulting in higher detonation parameters. 1-NAMT was thoroughly analyzed by single-crystal diffraction experiments accompanied by elemental analysis, IR spectroscopy, and multinuclear (1H, 13C, and 14N) NMR measurements. The thermal behavior of 1-NAMT was analyzed by differential thermal analysis supported by thermogravimetric analysis. Furthermore, energetic coordination compounds (ECCs) of Cu with different inorganic (e.g., nitrate, chlorate, and perchlorate) and nitroaromatic anions (e.g., picrate and styphnate) were synthesized and thoroughly analyzed. It is shown that the formation of ECCs with nitroaromatic anions (Tdec ∼ 180 °C) is a suitable strategy to improve the rather low thermal stability of 1-NAMT (125 °C).

Nitrocarbamoyl Azide O2NN(H)C(O)N3: A Stable but Highly Energetic Member of the Carbonyl Azide Family.

The diazotization of nitrosemicarbazide (1) resulted in the formation and isolation of nitrocarbamoyl azide (2), which was thoroughly characterized by spectroscopic and structural methods. This compound shows surprising stability but also high reactivity and sensitivity, with a melting point of 72 °C and a detonative decomposition point at 83 °C. In addition, five selected salts were synthesized by careful deprotonation. The decomposition mechanism of 2 in solution was investigated and could be clarified by performing experiments using methanol and hydrazine as trapping reagents. The energetic and physicochemical properties of all these compounds were investigated and classified.

A Smart Access to the Dinitramide Anion - The Use of Dinitraminic Acid for the Preparation of Nitrogen-Rich Energetic Copper(II) Complexes.

Dinitraminic acid (HN(NO2 )2 , HDN) was prepared by ion exchange chromatography and acid-base reaction with basic copper(II) carbonate allowed the in situ preparation of copper(II) dinitramide, which was reacted with twelve nitrogen-rich ligands, for example, 4-amino-1,2,4-triazole, 1-methyl-5H-tetrazole, di(5H-tetrazolyl)-methane/-ethane/-propane/-butane. Nine of the complexes were investigated by low-temperature X-ray diffraction. In addition, all compounds were investigated by infrared spectroscopy (IR), differential thermal analysis (DTA), elemental analysis (EA) and thermogravimetric analysis (TGA) for selected compounds. Furthermore, investigations of the materials were carried out regarding their sensitivity toward impact (IS), friction (FS), ball drop impact (BDIS) and electrostatic discharge (ESD). In addition, hot plate and hot needle tests were performed. Complex [Cu(AMT)4 (H2 O)](DN)2 , based on 1-amino-5-methyltetrazole (AMT), is most outstanding for its detonative behavior and thus also capable of initiating PETN in classical initiation experiments. Laser ignition experiments at a wavelength of 915 nm were performed for all substances and solid-state UV-Vis spectra were recorded to apprehend the ignition mechanism.

Polyazido-methyl Derivatives of Prominent Oxadiazole and Isoxazole Scaffolds: Synthesis, Explosive Properties, and Evaluation.

Recently, different nitrato-methyl-substituted oxadiazoles have been described as potential melt-cast explosives. In this work, corresponding N-O heterocyclic-based compounds with azido-methyl functionalities were synthesized. In each case, the explosophoric azide group is inserted by chlorine-azide exchange during the last synthetic step. All synthesized compounds show interesting characteristics for various applications in the field of energetic materials as energetic plasticizers or as melt-cast explosives. The compounds were extensively analyzed by IR, EA DTA, and multinuclear NMR spectroscopy. Furthermore, the solid compounds 4,4',5,5'-tetrakis(azidomethyl)-3,3'-bisisoxazole (2) and 3,3'-bis(azidomethyl)-5,5'-bis(1,2,4-oxadiazole) (4) were characterized using X-ray diffraction. In addition, the sensitivities toward friction and impact were determined with BAM standard techniques, and the energetic performances of all synthesized azido-methyl compounds were calculated using the EXPLO5 code. The properties were compared to recently published, structurally related compounds.

Investigation of Ethylenedinitramine as a Versatile Building Block in Energetic Salts, Cocrystals, and Coordination Compounds.

Ethylenedinitramine (H2EDN, 1) was prepared in a simple manner and with a high overall yield by direct nitration of 2-imidazolidinone using 100% HNO3 at 0 °C and subsequent hydrolysis in water at 100 °C. The versatility of 1 allows its application as starting material for a broad range of different materials. It was used for the preparation of both various salts and cocrystalline materials incorporating varying amounts of the TATOT moiety. Furthermore, H2EDN was successfully applied in the concept of energetic coordination compounds (ECCs) resulting in five copper(II) and two silver(I) complexes. A reaction path for the direct precipitation or slow crystallization of 17 different salts, including several alkali, alkaline earth, silver, and nitrogen-rich samples, is presented. The substances were extensively characterized by low-temperature single-crystal X-ray diffraction, elemental analysis (EA), IR spectroscopy, differential thermal analysis (DTA), and thermogravimetric analysis (TGA), proving their high thermal stability, especially of the alkali salts. In addition, 1 and all salts were characterized by 1H, 13C, and 14N NMR, whereas 1 was also investigated using the beneficial 1H-15N HMBC NMR spectroscopy. The sensitivities toward various mechanical stimuli according to BAM standard methods, as well as ball drop impact and electrostatic discharge (ESD) were determined using the BAM 1-out-6 method. Hot plate and hot needle tests were performed, followed by further characterization of the copper(II)-based ECCs through laser ignition experiments and UV-vis spectroscopy, offering new candidates for nontoxic, less sensitive laser-ignitable materials. Several detonation parameters were calculated using EXPLO5 (V6.05.02).

Low-Power Laser Ignition of an Antenna-Type Secondary Energetic Copper Complex: Synthesis, Characterization, Evaluation, and Ignition Mechanism Studies.

In recent years, development of new energetic compounds and formulations, suitable for ignition with relatively low-power lasers, is a highly active and competitive field of research. The main goal of these efforts is focused on achieving and providing much safer solutions for various detonator and initiator systems. In this work, we prepared, characterized, and studied thermal and ignition properties of a new laser-ignitable compound, based on the 5,6-bis(ethylnitroamino)-N'2,N'3-dihydroxypyrazine-2,3-bis(carboximidamide) (DS3) proligand. This new energetic proligand was prepared in three steps, starting with 5,6-bis(ethylamino)-pyrazine-2,3-dicarbonitrile. Crystallography studies of the DS3-derived Cu(II) complex (DS4) revealed a unique stacked antenna-type structure of the latter compound. DS4 has an exothermal temperature of 154.5 °C and was calculated to exhibit a velocity of detonation of 6.36 km·s-1 and a detonation pressure of 15.21 GPa. DS4 showed properties of a secondary explosive, having sensitivity to impact, friction, and electrostatic discharge of 8 J, 360 N, and 12 mJ, respectively. In order to study the mechanism of ignition by a laser (using a diode laser, 915 nm), we conducted a set of experiments that enabled us to characterize a photothermal ignition mechanism. Furthermore, we found that a single pulse, with a time duration of 1 ms and with a total energy of 4.6 mJ, was sufficient for achieving a consistent and full ignition of DS4. Dual-pulse experiments, with variable time intervals between the laser pulses, showed that DS4 undergoes ignition via a photothermal mechanism. Finally, calculating the chemical mechanism of the formation of the complex DS4 and modeling its anhydrous and hydrated crystal structures (density functional theory calculations using Gaussian and HASEM software) allowed us to pinpoint a more precise location of water molecules in experimental crystallographic data. These results suggest that DS4 has potential for further development to a higher technology readiness level and for integration into small-size safe detonator systems as for many civil, aerospace, and defense applications.

Closing the Gap: Synthesis of Three Isomeric N,N-Ditetrazolymethane Ligands and Their Coordination Proficiency in Adaptable Laser Responsive Copper(II) and Sensitive Silver(I) Complexes.

N,N-Substituted ditetrazolylalkanes are widely used molecules in the field of coordination chemistry and are known with different alkyl chain lengths. The missing fragment within this row is presented by the elementary methylene-bridged ditetrazoles. The three different isomers (di(tetrazol-1-yl)methane (1,1-dtm, 1), (tetrazol-1-yl)(tetrazol-2-yl)methane (1,2-dtm, 2), and di(tetrazol-2-yl)methane (2,2-dtm, 3)) were synthesized in a convenient one-step reaction. All of them were successfully incorporated as neutral ligands in 15 new energetic coordination compounds (ECC) based on Cu2+ and Ag+ as well as different anions (nitrate, picrate (PA), styphnate (TNR), trinitrophloroglucinate (TNPG), and perchlorate) revealing an extraordinary coordination behavior of the ligands compared to other 5H-ditetrazolylalkanes. All compounds were extensively characterized using single-crystal X-ray diffraction experiments, infrared spectroscopy (IR), elemental analysis (EA), and differential thermal analysis (DTA). Furthermore, the sensitivities were determined using standard techniques, and Hirshfeld surface calculations of the ligands were applied to explain their significant divergences to external stimuli. The ECC possess very good exothermic decomposition temperatures up to 242 °C. The ignition of all colored complexes was tested in laser experiments, and two copper(II) perchlorate compounds showed promising results in classic initiation capability tests using pentaerythritol tetranitrate (PETN).

Taming the Dragon: Complexation of Silver Fulminate with Nitrogen-Rich Azole Ligands.

The almost ancient and very sensitive silver fulminate (SF), which was involved in the establishment of fundamental chemical concepts, was desensitized for the first time with different nitrogen-rich triazoles and tetrazoles, yielding SF complexes [Agx(CNO)x(N-Ligand)y] (x = 1-4; y = 1-3). These were accurately characterized (X-ray diffraction, scanning electron microscopy, IR, elemental analysis, differential thermal analysis, and thermogravimetric analysis) and investigated concerning their energetic character. The highly energetic coordination compounds suddenly show, in contrast to SF, sensitivities in a manageable range and are therefore safer to handle. In particular, compounds [Ag4(CNO)4(BTRI)] [3; BTRI = 4,4'-bis(1,2,4-triazole)] and [Ag4(CNO)4(2,2-dtp)] [8; 2,2-dtp = 1,3-di(tetrazol-1-yl)propane] show values in the range of desired lead styphnate alternatives with similar energetic performances. The crystal structure experiments reveal silver cluster formation in all complexes with distinct argentophilic interactions close to 2.77 Å. Furthermore, it was possible to synthesize 8 in a one-pot reaction, avoiding the isolation of highly sensitive SF.

Refinement of Copper(II) Azide with 1-Alkyl-5H-tetrazoles: Adaptable Energetic Complexes.

A concept for stabilizing highly sensitive and explosive copper(II) azide with 1-N-substituted tetrazoles is described. It was possible to stabilize the system by the use of highly endothermic, nitrogen-rich ligands. The sensitivities of the resulting energetic copper coordination compounds can be tuned further by variation of the alkyl chain of the ligands and by phlegmatization of the complexes with classical additives during the synthesis. It is demonstrated, using the compound based on 1-methyl-5H-tetrazole ([Cu(N3 )2 (MTZ)], 1) that this class of complexes can be applied as a potential replacement for both lead azide (LA) and lead styphnate (LS). The complex was extensively investigated according to its chemical (elemental analysis, single-crystal and powder X-ray diffraction, IR spectroscopy, scanning electron microscopy) and physico-chemical properties (differential thermal analysis, sensitivities towards impact, friction, and electrostatic discharge) compared to pure copper(II) azide.

1-AminoTriazole Transition-Metal Complexes as Laser-Ignitable and Lead-Free Primary Explosives.

This unique complex study describes two isomeric aminotriazoles as auspicious nitrogen-rich ligands for energetic coordination compounds (ECCs) to replace the commonly used highly poisonous and environmentally harmful lead-based primary explosives. The triazoles were obtained by easily scalable and convenient synthetic routes starting solely from commercially available starting materials. 1-Amino-1,2,3-triazole (1, 1-ATRI) and, for the first time, 1-amino-1,2,4-triazole (2, 1A-1,2,4-TRI) were employed as ligands to form highly energetic transition-metal(II) complexes. The desired characteristics could be altered successively by using various nonpoisonous metal(II) centers (Cu2+ , Mn2+ , Fe2+ , and Zn2+ ) and anions (Cl- , NO3 - , ClO3 - , ClO4 - , picrate, styphnate, 2,4,6-trinitro-3-hydroxyphenolate, and 2,4,6-trinitro-3,5-dihydroxyphenolate). The 14 synthesized coordination compounds were characterized comprehensively by XRD, IR and UV/Vis spectroscopy, elemental analysis, and differential thermal and thermogravimetric analyses. Ball-drop impact, electrostatic discharge (ESD), and mechanical (impact and friction) sensitivities were determined according to BAM standard methods. In addition to laser ignition experiments, selected ECCs were evaluated in classical secondary explosive initiation tests (detonators filled with pentaerythritol tetranitrate (nitropenta)), which revealed their enormous potential and proved them to be very attractive for future applications in explosives.

Copper(II) Chlorate Complexes: The Renaissance of a Forgotten and Misjudged Energetic Anion.

A convenient synthetic route toward new copper(II) chlorate complexes with potential use in modern advanced ignition or initiation systems is described. Obtained compounds were not only accurately characterized (XRD, IR, UV/Vis EA and DTA) but also investigated for their energetic character (sensitivities, initiation capability and laser ignition). The copper 4-aminotriazolyl chlorate complex showed excellent initiation of PETN, while also being thermally stable and safe to handle. Solid-state UV-Vis measurements were performed to get a possible insight toward the laser initiation mechanism. In contrast to expectations, the presented copper(II) chlorate energetic coordination compounds show manageable sensitivities that can be tamed or boosted by the appropriate choice of nitrogen-rich ligands.

Methylsemicarbazide as a Ligand in Late 3d Transition Metal Complexes.

Most ignition and initiation systems nowadays still contain poisonous chemicals such as lead styphnate and lead azide but also chromates and other compounds of high concern. Therefore, methylsemicarbazide (1, MSC), which can be prepared in a one-step reaction and in an extraordinary high yield of 95 %, has been evaluated as ligand in energetic coordination compounds. For the first time 25 new transition metal complexes (Mn2+ , Ni2+ , Co2+ , Cu2+ , and Zn2+ ) using methylsemicarbazide (1) as the ligand were prepared and comprehensively analyzed by, for example, XRD, IR, EA, UV/Vis and DSC/DTA/TGA. Many show a strong energetic character, which can be tuned by using different anions such as Cl- , SO42- , NO3- , ClO4- , picrate or styphnate. Selected compounds were additionally evaluated as lead-free primary explosives in initiation tests (nitropenta filled detonators) and in laser ignition systems. Especially compound 7 showed very promising results during these tests and could be a potential candidate for future applications.

Nitrogen-Rich Copper(II) Bromate Complexes: an Exotic Class of Primary Explosives †.

Because of the ongoing very challenging search for potential replacements of the currently used toxic lead-based primary explosives, new synthetic strategies have to be developed. In particular, the smart concept of energetic coordination compounds (ECC) has proven to hold great potential to solve this difficult and complex problem. The herein-described approach combines the exotic and neglected class of copper(II) bromate ECC with different environmentally friendly nitrogen-rich heterocycles, which exhibit the energetic properties of powerful primary explosives. The concept is the simple adjustment of the energetic properties of the complexes through alteration of the corresponding azoles. Six new copper(II) bromate complexes with reasonable sensitivities are featured in this study, which were synthesized in a practical and straightforward fashion, assured through easy access to copper(II) bromate obtained by metathesis reaction. Obtained compounds were comprehensively characterized through various analytical methods such as low-temperature X-ray diffraction, IR spectroscopy, and elemental analysis. Their sensitivities toward impact and friction were assessed through BAM standard techniques, together with their sensitivity against electrostatic discharge. Evaluation of the energetic properties of the newly synthesized compounds included examination of the respective thermal stabilities by differential thermal analysis. Furthermore, the complexes were tested regarding their behavior toward laser irradiation. Additionally, to receive insight into a possible correlation between the laser-investigated compounds' optical absorption and their ability to ignite by exposure to laser irradiation, UV-vis-near-IR spectra were recorded.