Browsing by Author "Aghaei Hakkak, Rouzbeh"

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    Synthesis and characterization of high-energy anti-perovskite compounds Cs3X[B12H12] based on cesium dodecahydro-closo-borate with molecular oxoanions (X- = [NO3]-, [ClO3]- and [ClO4]-)
    (2024) Aghaei Hakkak, Rouzbeh; Tiritiris, Ioannis; Schleid, Thomas
    Three novel anti-perovskite compounds, formulated as Cs3X[B12H12] (X = [NO3], [ClO3], and [ClO4]), were successfully synthesized through the direct mixing of aqueous solutions containing Cs2[B12H12] and CsX (X: [NO3], [ClO3], [ClO4]), followed by isothermal evaporation. All three compounds crystallize in the orthorhombic space group Pnma, exhibiting relatively similar unit-cell parameters (e.g., Cs3[ClO3][B12H12]: a = 841.25(5) pm, b = 1070.31(6) pm, c = 1776.84(9) pm). The crystal structures were determined using single-crystal X-ray diffraction, revealing a distorted hexagonal anti-perovskite order for each. Thermal analysis indicated that the placing oxidizing anions X into the 3 Cs+ + [B12H12]2 blend leads to a reduction in the thermal stability of the resulting anti-perovskites Cs3X[B12H12] as compared to pure Cs2[B12H12], so thermal decomposition commences at lower temperatures, ranging from 320 to 440 C. Remarkably, the examination of the energy release through DSC studies revealed that these compounds are capable of setting free a substantial amount of energy, up to 2000 J/g, upon their structural collapse under an inert-gas atmosphere (N2). These three compounds represent pioneering members of the first ever anti-perovskite high-energy compounds based on hydro-closo-borates.
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    Two new energetic hexagonal anti-perovskites (N2H5)3X[B12H12] · H2O (X- = [NO3]- and [ClO4]-) : crystal structure, vibrational spectra, and thermal decomposition
    (2024) Aghaei Hakkak, Rouzbeh; Klapötke, Thomas M.; Schleid, Thomas
    Two novel energetic anti-perovskite compounds with the chemical formula (N2H5)3X[B12H12] · H2O, where X- is either [NO3]− or [ClO4]−, were successfully synthesized. Both dodecahydro-closo-dodecaborates crystallize orthorhombically in the space group Cmc21, exhibiting relatively similar lattice parameters ((N2H5)3[NO3][B12H12] · H2O: a = 915.94(5), b = 1817.45(9), c = 952.67(5) pm, (N2H5)3[ClO4][B12H12] · H2O: a = 1040.51(6), b = 1757.68(9), c = 942.34(5) pm both for Z = 4). Their synthesis involved a two-step process: first, Cs2[B12H12] passed through a cation exchange column to yield the acidic form of the dodecahydro-closo-dodecaborate, (H3O)2[B12H12]. This aqueous solution was subsequently neutralized with hydrazinium hydroxide and mixed with the corresponding water-dissolved hydrazinium salt (nitrate or perchlorate). Characterization of the obtained crystals was performed by single-crystal X-ray diffraction and Raman spectroscopy as well as thermal analyses (TG-DTA and DSC). The crystal structure determinations revealed that both compounds adopt a hexagonal anti-perovskite structure, distorted by the presence of water molecules. These compounds containing oxidizing oxoanions demonstrate a remarkable ability to release large amounts of energy (almost 2100 J/g) upon thermal decomposition.