Electronic Structure Studies of Tetrazolium-Based Ionic Liquids

Abstract

New energetic ionic liquids are investigated as potential high energy density materials. Ionic liquids are composed of large, charge-diffuse cations, coupled with various (usually oxygen containing) anions. In this work, calculations have been performed on the tetrazolium cation with a variety of substituents. Density functional theory (DFT) with the B3LYP functional, using the 6-311G(d,p) basis set was used to optimize geometries. Improved treatment of dynamic electron correlation was obtained using second-order perturbation theory (MP2). Heats of formation of the cation with different substituent groups were calculated using isodesmic reactions and Gaussian-2 calculations on the reactants. The cation was paired with oxygen rich anions ClO4-, NO3-, or N(NO2)2-and those structures were optimized using both DFT and MP2. The reaction pathway for proton transfer from the cation to the anion was investigated. Disciplines Chemistry CommentsReprinted (adapted) ReceiVed: February 9, 2006; In Final Form: April 3, 2006 New energetic ionic liquids are investigated as potential high energy density materials. Ionic liquids are composed of large, charge-diffuse cations, coupled with various (usually oxygen containing) anions. In this work, calculations have been performed on the tetrazolium cation with a variety of substituents. Density functional theory (DFT) with the B3LYP functional, using the 6-311G(d,p) basis set was used to optimize geometries. Improved treatment of dynamic electron correlation was obtained using second-order perturbation theory (MP2). Heats of formation of the cation with different substituent groups were calculated using isodesmic reactions and Gaussian-2 calculations on the reactants. The cation was paired with oxygen rich anions ClO 4 -, NO 3 -, or N(NO 2 ) 2 -and those structures were optimized using both DFT and MP2. The reaction pathway for proton transfer from the cation to the anion was investigated.

Pentazole-Based Energetic Ionic Liquids: A Computational Study

“…In comparison, the predicted heats of formation for the parent triazolium and tetrazolium cations are 2.8 15 and 3.6 16 kcal/g, respectively. This is further evidence that these pentazole ions are relatively unstable and, therefore, will likely be difficult to synthesize, isolate, and detect much like their parent neutral pentazole.…”

“…Recently, theoretical studies have been completed on ionic liquids based on the triazolium (N 3 C 2 H 4 + ) and tetrazolium (N 4 CH 3 + ) cations, combined with anions such as dinitramide (N(NO 2 ) 2 -), nitrate (NO 3 -), and perchlorate (ClO 4 -). 15,16 Another approach to increasing the energy of the cations is to introduce high-energy substituents into the ring, such as azido (-N 3 ) and nitro (-NO 2 ). The present work is a systematic investigation of the structures and energetics of possible ionic liquids formed by protonated pentazole cations, RN 5 H + , and the dinitramide, nitrate, and perchlorate anions.…”

Chemical Kinetics Interpretation of Hypergolicity of Ionic Liquid-Based Systems

“…However, Baranyai et al (2004) do not observe the formation of species normally associated with the proton transfer process. Zorn et al (2006) deduced from their calculations on protic tetrazolium-based ionic liquids that when a cation is paired with an oxygen rich anion, an isolated gas phase ion-pair was not generally found to be stable. In fact, a proton transfers without barrier from the cation to the anion to form a neutral pair.…”

Ultrafast Photogeneration of a Tetrazolinyl Radical

“…[16] Quantum-chemical calculations of the LUMO of TTC [17] support the possibility of ring-opening at the same position as required for TPF formation, due to a lack of electron density at the center of this bond; this bond also exhibits the lowest ground-state bond order in the tetrazolium ring. [18] If the ring is opened, the conjugation is interrupted by going from the aromatic TTC to ro-TTC, so that the absorption characteristics will drastically change. The absorption around 520 nm observed for 1 resembles the absorption of a tetraaza pentadienium cation [19] for which the NÀN=CÀN=N + backbone is identical to ro-TTC.…”