The main challenge in designing new energetic materials is to find a good balance between four seemingly incompatible requirements, namely, high-energy content, low sensitivity, low production costs and less-polluting content. Fused nitrogen heterocycles of imidazole and pyrimidine, such as acyclovir and guanine, may offer interesting features due to the combination of a coplanar framework and a large conjugate system, which contribute to a reduced sensitivity, and a number of energetic bonds that can be increased by the introduction of explosophore substituents. In this work, to evaluate the potential of acyclovir and guanine derivatives as energetic materials, density functional theory (DFT) calculations were carried out to investigate the influence of the type and position of the explosophore substituent groups –, –, –, –, –, and on the energetic properties and chemical reactivity of 91 acyclovir- and guanine-based molecules, including thirty one nitramines, three nitroheterocycles, seventeen azides, seventeen nitrate esters, seventeen nitriles, three azo and three azoxy compounds. Several molecular properties were computed, including the chemical reactivity, the heat of formation and the detonation velocities and pressures using semiempirical equations. Among the molecules with no bridge groups, we found that, except for cyano group, position 4 were the most stable for acyclovir derivatives, whereas, except for the azido group, position 2 and 5 provided the most stable compounds for guanine derivatives. Among the bridged derivatives, depending on the molecule and positions, the nitrate esters and the nitro derivatives were more stable. In comparison with the parent compounds, calculations showed that the heat of formation (HOF) increased the most with azido and cyano groups, the density increased substantially with nitrate esters, nitro and nitramino groups, and the detonation velocities and pressures increased the most with nitrate ester, nitro and nitramino groups. Although azo groups resulted in higher HOFs than azoxy groups, azoxy derivatives showed superior values in terms of density, heat of maximum detonation, detonation velocity and pressure. Four nitrate esters (GD134, GD245, AZOXYGD13 and AZOXYGD25) displayed higher values of detonation velocity and pressure than RDX. The designed nitramines are less sensitive to impact than RDX. Except for GD134 and GD245, all guanine-based nitrate esters, with no bridge linkages, are expected to be less sensitive to impact than TNT. Due to the combination of good performance and stability, the compounds GD25, GD13, GD45, GD34, and GD14 have considerable potential as energetic materials. Therefore, their synthesis and further investigation are recommended.

中文翻译：

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阿昔洛韦和鸟嘌呤衍生物取代基效应在含能材料中应用的密度泛函理论研究

设计新型含能材料的主要挑战是在高能量含量、低灵敏度、低生产成本和低污染含量这四个看似不相容的要求之间找到良好的平衡。咪唑和嘧啶的稠合氮杂环，例如阿昔洛韦和鸟嘌呤，由于共面框架和大共轭系统的结合，可能会提供有趣的特征，这有助于降低灵敏度，并且可以通过以下方式增加许多能量键引入爆炸基团取代基。在这项工作中，为了评估阿昔洛韦和鸟嘌呤衍生物作为含能材料的潜力，进行了密度泛函理论（DFT）计算，以研究爆炸基团取代基类型和位置的影响 -, -, -, -, - ，以及91种阿昔洛韦和鸟嘌呤分子的能量性质和化学反应性，包括31种硝胺、3种硝基杂环、17种叠氮化物、17种硝酸酯、17种腈、3种偶氮和3种氧化偶氮化合物。使用半经验方程计算了几种分子特性，包括化学反应性、形成热以及爆炸速度和压力。在没有桥基的分子中，我们发现，除了氰基之外，阿昔洛韦衍生物的4位是最稳定的，而除了叠氮基之外，鸟嘌呤衍生物的2位和5位是最稳定的化合物。在桥联衍生物中，根据分子和位置的不同，硝酸酯和硝基衍生物更稳定。与母体化合物相比，计算表明，叠氮基和氰基的形成热（HOF）增加最多，硝酸酯、硝基和硝氨基基团的密度显着增加，硝酸盐的爆速和压力增加最多酯基、硝基和硝氨基。尽管偶氮基团比氧化偶氮基团产生更高的 HOF，但氧化偶氮基衍生物在密度、最大爆炸热、爆速和压力方面表现出更优异的值。四种硝酸酯（GD134、GD245、AZOXYGD13 和 AZOXYGD25）显示出比 RDX 更高的爆速和压力值。设计的硝胺对冲击的敏感度低于 RDX。除 GD134 和 GD245 外，所有没有桥键的鸟嘌呤基硝酸酯预计对冲击的敏感度低于 TNT。由于良好的性能和稳定性的结合，化合物GD25、GD13、GD45、GD34和GD14作为含能材料具有相当大的潜力。因此，建议对其进行合成和进一步研究。