四嗪类高氮化合物结构对热分解机理影响的理论研究

Theoretical Study on Effect of Tetrazine Structures on Their Thermal Decomposition Mechanisms

采用从头算分子动力学方法,对均四嗪分子及其5种衍生物分子的热分解轨迹进行了模拟,获得了它们的各种热分解途径及其难易程度。用密度泛涵理论在B3LYP/6-311G(d,p)水平下计算了各稳定点和过渡态的几何结构和能量,得到了各反应途径的能垒高度,从能量的角度对从头算分子动力学模拟结果进行了验证。获得了不含取代基的均四嗪分子的热分解机理,即协同的三键断裂,与其光分解机理一致。此外,还得到了5种不同类型的取代基对四嗪环的开环方式、稳定性以及对四嗪类高氮化合物热分解机理的影响规律。当取代基的稳定性高于四嗪环的稳定性时,该化合物首先发生开环反应;反之,则首先发生取代基反应。另外还获得了分子间反应对四嗪类高氮化合物热分解机理影响的一些较新的结论。

The thermal decomposition trajectories of s-tetrazine molecule and its five derivatives were simulated by ab initio molecular dynamics （AIMD） method to acquire the possible decomposition pathways and identify their relative importance. The reaction channels were studied by density functional theory （DFT） at B3LYP/6-311G（d, p） level to locate the local minimum points and the transition structures, and to verify the result of AIMD in terms of energy, suggesting that s-tetrazine molecule underwent concerted triple dissociation, just as its photolysis mechanism. The effect rules of five different substituents on the modes of tetrazine ring opening, the stability of the tetrazine ring and thermal decomposition mechanism of tetrazine derivatives were obtained. If the stability of the substituent is better than that of the tetrazine ring, decomposition occurs first through the ring breaking. Otherwise, the substituent reactions first take place. Moreover, some new conclusions about the effect of intermolecular reaction on the thermal decomposition mechanisms of tetrazines were achieved.