具有四唑环的电子激发的富氮高能盐单分子分解的初始机理：（NH4）2BT和TAGzT,The Journal of Chemical Physics

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具有四唑环的电子激发的富氮高能盐单分子分解的初始机理：（NH4）2BT和TAGzT
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2016-08-10 15:52:35 , DOI: 10.1063/1.4960345
Bing Yuan ₁ , Elliot R. Bernstein ₁

Affiliation

富氮高能盐分子双（铵）5,5'-双_四唑酸酯（NH ₄）₂ BT和双（三氨基胍）5,5'-偶氮四唑酸酯TAGz的单分子分解已通过283 nm激光激发进行了探索。在紫外线激发之后，观察到具有低温旋转温度（<30 K）的N ₂分子是初始分解产物。在完全活动空间自洽场（CASSCF）级别上探索了两个电子激发的盐分子的初始分解机理。CASSCF（12,8）/ 6-31G（d）（（NH ₄）₂BT）和ONIOM（CASSCF / 6-31G（d）：UFF）（TAGzT）水平表明，圆锥形相交在分解机理中起着至关重要的作用，因为它们在上下电子态之间提供了非绝热，超快的无辐射内部转换。四唑环在S ₁激发态表面上打开，并通过圆锥形交点（S ₁ / S ₀）_CI，N ₂打开。产物在基态势能表面上形成而没有旋转激发。四唑环在N2-N3环键处以最低的能垒打开：C-N环键的开口具有比任何N-N环键更高的能垒：这与其他氮原子的发现相符。丰富的中性有机含能材料。TAGzT可以通过四唑环的开环或连接其两个四唑环的N = N基团产生N ₂。尽管如此，四唑环的打开具有低得多的能垒。N _2的振动温度根据理论预测，产品很热。迄今为止研究的所有富氮高能材料（包括中性有机分子和盐）的四唑环打开的能垒在0.31至2.71 eV的范围内。具有解离的N ₂产物的这些系统的最终分子结构的能量在-1.86至3.11 eV的范围内。高能盐和中性富氮高能材料之间的主要区别是高能盐通常具有较低的激发能。

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Initial mechanisms for the unimolecular decomposition of electronically excited nitrogen-rich energetic salts with tetrazole rings: (NH4)2BT and TAGzT

Unimolecular decomposition of nitrogen-rich energetic salt molecules bis(ammonium)5,5′-bistetrazolate (NH₄)₂BT and bis(triaminoguanidinium) 5,5′-azotetrazolate TAGzT, has been explored via 283 nm laser excitation. The N₂ molecule, with a cold rotational temperature (<30 K), is observed as an initial decomposition product, subsequent to UV excitation. Initial decomposition mechanisms for the two electronically excited salt molecules are explored at the complete active space self-consistent field (CASSCF) level. Potential energy surface calculations at the CASSCF(12,8)/6-31G(d) ((NH₄)₂BT) and ONIOM (CASSCF/6-31G(d):UFF) (TAGzT) levels illustrate that conical intersections play an essential role in the decomposition mechanism as they provide non-adiabatic, ultrafast radiationless internal conversion between upper and lower electronic states. The tetrazole ring opens on the S₁ excited state surface and, through conical intersections (S₁/S₀)_CI, N₂ product is formed on the ground state potential energy surface without rotational excitation. The tetrazole rings open at the N2—N3 ring bond with the lowest energy barrier: the C—N ring bond opening has a higher energy barrier than that for any of the N—N ring bonds: this is consistent with findings for other nitrogen-rich neutral organic energetic materials. TAGzT can produce N₂ either by the opening of tetrazole ring or from the N=N group linking its two tetrazole rings. Nonetheless, opening of a tetrazole ring has a much lower energy barrier. Vibrational temperatures of N₂ products are hot based on theoretical predictions. Energy barriers for opening of the tetrazole ring for all the nitrogen-rich energetic materials studied thus far, including both neutral organic molecules and salts, are in the range from 0.31 to 2.71 eV. Energy of the final molecular structure of these systems with dissociated N₂ product is in the range from −1.86 to 3.11 eV. The main difference between energetic salts and neutral nitrogen-rich energetic material is that energetic salts usually have lower excitation energy.

更新日期：2016-08-11

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