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Published on: June 10, 2021
Comparison of Functionalized Lithium Dihydrobis(azolyl)borates with Their Corresponding Azolates as Environmentally
Alicia M W Dufter1, Thomas M Klapötke1, Magdalena Rusan1
1Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany.
Abstract:
The recent awareness of the impact of strontium on health has stimulated research efforts on lithium-based red pyrotechnic colorants. We have previously shown lithium dihydrobis(azolyl)borates to be promising candidates due to their favorable adjustment to a reductive and low-temperature flame atmosphere. These compounds are assumed to be sufficiently stable only if the pKa values of the heterocycles are between 5 and 20. Apart from their acidities, functionalization of 1H-tetrazole and 1H-pyrazole with nitro or amino groups, respectively, tailors the oxygen balances of the resulting Lewis acid base adducts to enhance the fuel-rich flame environment or to make them oxidizing agents. This work determines whether the lithium salts of dihydrobis(3-nitropyrazol-1-yl)borate and dihydrobis(5-aminotetrazol-1-yl)borate are suitable replacements for strontium-containing color imparters. Furthermore, the influence of potentially green-light-producing boron is evaluated by comparing the emissions of the lithium borates and the corresponding lithium azolates.
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