Showing papers on "Triazene published in 2018"

Preparation and characteristics of 1,2,4-oxadiazole-derived energetic ionic salts with nitrogen linkages

Abstract: A new family of energetic ionic salts containing a 1,2,4-oxadiazole ring and an amino or triazene linkage were synthesized by the oxidation of 3-nitro-5-amino-1,2,4-oxadiazole (NOA) with sodium dichloroisocyanurate (SDCI) affording sodium bis(3-nitro-1,2,4-oxadiazol-5-yl)amide (2) and sodium 1,3-bis(3-nitro-1,2,4-oxadiazol-5-yl)triaz-2-en-1-ide (3) followed by cation metathesis. Their molecular structures were fully characterized by 1H and 13C NMR, MS and IR spectroscopy, while three ionic salts 4, 5 and 7 along with two sodium salt precursors 2 and 3 were confirmed by single-crystal X-ray diffraction. Differential scanning calorimetry (DSC) was employed to investigate the thermal stability of these ionic salts, revealing moderate onset decomposition temperatures ranging from 166 °C to 249 °C. By using a fall hammer test, most salts were found to exhibit low impact sensitivities. Guanidinium bis(3-nitro-1,2,4-oxadiazol-5-yl)amide (4) exhibits good performance with acceptable detonation properties (D: 8351 m s−1, P: 29.0 GPa), good stability (Td: 241 °C, onset) and low impact sensitivity (IS > 40 J).

Synthesis, characterization and electrocatalytic performance of a dinuclear triazenidosilver(I) complex for hydrogen production

Abstract: Our group has developed a series of molecular electrocatalysts for hydrogen generation based on triazenido–metal complexes (cobalt, copper, etc.). In this paper, we first present the electrocatalytic performance of a new dinuclear silver complex, [Ag2(L)2], formed by the reaction of the triazenido ligand 1-[(2-carboxymethyl)benzene]-3-[(2-methoxy)benzene]triazene (HL) with AgNO3. At room temperature, the silver complex shows photoluminescence at 653 nm. The electrocatalytic systems based on this silver complex can afford 106.57 and 1536.36 moles of hydrogen per mole of catalyst per hour from acetic acid at an overpotential (OP) of 991.6 mV and from a neutral aqueous buffer (pH = 7.0) at an OP of 837.6 mV, respectively. Electrochemical investigations show that both silver ion and triazenido ligand play a role in determining the catalytic activities of the electrocatalytic system.

How a linear triazene photoisomerizes in a volume-conserving fashion

Abstract: Understanding deactivation mechanisms of functional groups is a key step to design novel photo-active devices and molecular imaging agents. Here, we elucidate the photochemistry of linear triazenes, an extended analogue of the photo-switchable azo group, exemplarily for the widely used DNA-minor-groove binder berenil. Combining ultrafast spectroscopy and ab initio calculations unveils that the E-azo,s-trans structure of berenil predominates in the gas phase and in aqueous solution, and ADC(2) intrinsic reaction coordinate calculations disclose that the excited-state relaxation to the S1 minima/conical intersections follows a two-step mechanism: NN bond stretching followed by a bicycle-pedal rotation in the triazene bridge. Furthermore, studying the ground-state pathways shows that a fraction of the molecules relaxes back to the E-azo,s-trans isomer while the other part photoisomerizes to the Z-azo,s-trans via a hula-twist motion, as evidenced by experimental quantum yields of Φ ≈ 0.5 found for berenil in water, ethylene glycol, or bound to β-trypsin. Moreover, our studies show that while the excited-state relaxation is insensitive to the environment, the ground-state dynamics depend on biomolecular binding partners.

Synthesis [1-(4-acetylphenyl)-3-(2-methylphenyl)]triazene: NMR, Vibrational, X-ray Crystallography Characterization with HF/DFT Studies

Abstract: [1-(4-acetylphenyl)-3-(2-methylphenyl)]triazene (AMT) was synthesized by experimental methods, its chemical and spectrometric properties was studied by FT-IR, FT-Raman,1H-NMR,13C-NMR and X-ray singlecrystal diffraction methods. The obtained results showed that this structure hasorthorombic system with space group of pbca and eight molecules in unit cell. Its unit cell parameters comprise a=8.0665(2), b=8.0019(2) and c=21.5249(5). Then molecular number of [1-(4-acetylphenyl)-3-(2-methylphenyl)]triazene (AMT) structure has been studied by HF/DFT methods. However, FT-IR, FT-Raman,1H-NMR, 13C-NMR spectra were analyzed that the obtained results for vibrational spectra and amount of chemical shift correspond significantly with theoretical methods. Some structural parameters such as bonds length, bonds angle and dihedral angle were studied using theoretical and experimental methods. The parameters such as thermodynamical parameters, dipole moment, HOMO and LUMO energetic values, electrophilicity (ω), chemical potential(μ), chemical hardness(η) and max amount of electronic charge transfer (ΔNmax) are calculated for this compound in conclusion. The proposed methods were successfully applied to the determination of vibrational spectra, chemical shift amounts and structural parameters.

Synthesis, structure, magnetic and catalytic behavior of a dinuclear copper(II) complex with triazendio ligands

Abstract: A dinuclear copper(II) complex [Cu2L4] has been prepared by the reaction of CuCl2·2H2O and 1-[(2-iodo)benzene]-3-[benzothiazole] triazene (HL). The complex has been characterized by X-ray crystallography and by physico-chemical and spectroscopic methods. In the solid state, there is a significant antiferromagnetic coupling between the copper(II) centers with a coupling constant (J) of − 558 cm−1. In homogeneous solution, the complex shows electrocatalytic activities for hydrogen generation from both acetic acid and neutral buffer with a turnover frequency of 50 mol of H2 per mole of catalyst per hour (mol H2/mol catalyst/h) at an overpotential (OP) of 941.6 mV, and 502 mol H2/mol catalyst/h at an OP of 836.7 mV.

Investigating multistep continuous flow processes using diazonium salts

Abstract: This thesis describes the investigation of continuous flow processes that incorporate the generation and use of diazonium salts. In this manner, processes for the preparation of triazenes, indoles and acridones have been developed. Diazonium salts are potentially unstable and hazardous and have to be handled with care. The use of continuous flow processes enables the safe synthesis avoiding accumulation of large quantities. This is due to the possibility to intercept intermediates at a precise point in time within a closed system. Diazonium salts were prepared via in situ diazotization of anilines with isoamylnitrite. Triazenes were formed via the interception of diazonium salts with secondary amines. The process had to be carefully developed to avoid clogging and fouling of the reactor. 26 examples have been prepared. The thermal behavior of 13 triazenes has been compared to their corresponding tetrafluoroborate diazonium salts, which has shown they are significantly more stable. In addition, VT NMR analysis has been performed to explore restricted rotation around the triazene bond. Further developments have found that indoles can be prepared via reduction of diazonium salts to their corresponding hydrazine with ascorbic acid and subsequent Fischer indole reaction in a microwave reactor. The use of such a hybrid, machine assisted approach has enabled the formation of a library of indoles. In this manner, 33 examples have been synthesised including the drug Zolmitriptan and nine of its analogues. The formation of acridones from benzyne and anthranilates has been investigated. Benzyne was prepared via the thermal decomposition of benzenediazonium-2-carboxylate. The compound decomposes above ambient temperatures and is known to be explosive when dry. The formation of benzyne has been investigated using the Diels- Alder reaction with furan as a model reaction and then conditions were applied to a range of substrates to investigate the scope. Problems with solubility of starting materials, diazonium salts and products were encountered and partially solved through the screening of different solvents. Finally, an exothermic reaction was investigated under continuous flow reactions. Commercially available thermocouples and in line NMR analysis were used to facilitate process optimisation. The exothermic reaction explored was the reduction of TMSCF3 to TMSCF2H with NaBH4. The exotherm was monitored using external, commercially available thermocouples to realise the development of a safe reaction regime. The incorporation of in situ NMR measurements has allowed realtime assessment of reaction conversion as a correlation to the exotherm. With the combined monitoring approaches a safe scale up process has been established. A hybrid flow - batch approach was used to scale up the reaction and increase the space time yield compared to the previously reported batch reaction.