Researchers working in the area of rocket propulsion strive for environmental friendliness, low toxicity, and overall operability, as well as a performance level comparable with current propellant combinations such as hydrazine and N 2 O 4 . Maintaining high performance while lowering hazards is extremely difficult.All rocket oxidizers are hazardous by their very nature, and so reduction of those hazards, even though the resulting materials might not be completely harmless, is at the heart of green initiatives in propulsion. The corrosivity of nitric acid is well known, and, although N 2 O 4 is much less corrosive, it combines high toxicity with high vapor pressure. A significant step to a lower-toxicity bipropulsion system would be the demonstration of hypergolicity (spontaneous ignition) between an ionic liquid (IL), which is a paragon of low vapor toxicity, and a safer oxidizer. Apart from cryogens, hydrogen peroxide seems to be especially promising because of its high performance, less-toxic vapor and corrosivity, and its environmentally benign decomposition products, [1] which make handling this oxidizer considerably less difficult than N 2 O 4 or nitric acid.A high fuel performance can be fostered by light metals with large combustion energies and relatively light products. Elements with considerable performance advantages and nontoxic products are aluminum and boron. The need for light combustion products through the production of hydrogen gas and water vapor is fulfilled by a high hydrogen content. Aluminum and boron are well known for their ability to serve as hydrogen carriers in neutral and ionic molecules. Defense research in the 1960s focused extensively on the development of hydrogen-containing fuels with boron, aluminum, and other metals, [2] but was mainly concerned with neutral compounds that have high vapor toxicity. Their rich anionic chemistry combined with the design flexibility of ILs presage novel materials that have the potential to overcome problems that caused these promising propellants to be abandoned.To date, no IL has been reported to be hypergolic with H 2 O 2 , and first-generation hypergolic ILs based on dicyanamide, nitrocyanamide, and azide anions lack high hydrogen content. [3] We tested ILs from each class with 90 % and 98 % H 2 O 2 , and all failed to ignite. This result is hardly surprising since fuels that are hypergolic with nitric acid vastly outnumber those that ignite with N 2 O 4 . For many years, hydrazine was the only fuel hypergolic with H 2 O 2 . [4] Since solutions of lithium aluminum hydrides and LiBH 4 in ethers have demonstrated H 2 O 2 hypergolicity, [5] the same behavior from ILs with metal hydride anions might be expected. However, the development of energetic roomtemperature ILs (RTILs) with metal hydride anions involves a number of technical challenges. Simple metal hydride anions are poor liquefying agents. Furthermore, heterocyclic, unsaturated salts that feature imidazolium, triazolium, pyridinium, and other common IL cations are reduced by BH 4 À ions,...

Several imidazolium-based ionic liquid azides with saturated and unsaturated side chains were prepared, and their physical and structural properties were investigated. The reactivity of these new as well as some previously reported ionic liquid azides with strong oxidizers, N 2O 4 and inhibited, red-fuming-nitric acid (IRFNA), was studied.

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Ionic liquid azides from azidoethyl, alkyl, and alkenyl substituted derivatives of 1,2,4- and 1,2,3-amino-triazoles were prepared and examined for the first time to investigate their structural and physical properties. All reported salts possess melting points below 100 degrees C. The unique character of these newly discovered ionic liquid azides is based upon the fact that these molecules are not simple protonated salts like previously reported substituted hydrazinium azides. The presence of quaternary nitrogen confers both thermal stability and negligible volatility.

Recent progress is reported in development of ab initio computational methods for the electronic structures of molecules employing the many-electron eigenstates of constituent atoms in spectral-product forms. The approach provides a universal atomic-product description of the electronic structure of matter as an alternative to more commonly employed valence-bond- or molecular-orbital-based representations. The Hamiltonian matrix in this representation is seen to comprise a sum over atomic energies and a pairwise sum over Coulombic interaction terms that depend only on the separations of the individual atomic pairs. Overall electron antisymmetry can be enforced by unitary transformation when appropriate, rather than as a possibly encumbering or unnecessary global constraint. The matrix representative of the antisymmetrizer in the spectral-product basis, which is equivalent to the metric matrix of the corresponding explicitly antisymmetric basis, provides the required transformation to antisymmetric or linearly independent states after Hamiltonian evaluation. Particular attention is focused in the present report on properties of the metric matrix and on the atomic-product compositions of molecular eigenstates as described in the spectral-product representations. Illustrative calculations are reported for simple but prototypically important diatomic (H(2), CH) and triatomic (H(3), CH(2)) molecules employing algorithms and computer codes devised recently for this purpose. This particular implementation of the approach combines Slater-orbital-based one- and two-electron integral evaluations, valence-bond constructions of standard tableau functions and matrices, and transformations to atomic eigenstate-product representations. The calculated metric matrices and corresponding potential energy surfaces obtained in this way elucidate a number of aspects of the spectral-product development, including the nature of closure in the representation, the general redundancy or linear dependence of its explicitly antisymmetrized form, the convergence of the apparently disparate atomic-product and explicitly antisymmetrized atomic-product forms to a common invariant subspace, and the nature of a chemical bonding descriptor provided by the atomic-product compositions of molecular eigenstates. Concluding remarks indicate additional studies in progress and the prognosis for performing atomic spectral-product calculations more generally and efficiently.

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