美国华盛顿卡耐基研究所Goncharov Alexander F.团队报道了高压下六嗪环在聚硝酸钾中的稳定化。相关研究成果于2022年4月21日发表在《自然—化学》。

由于氮-氮键中储存的能量，多氮分子对高能量密度材料具有吸引力；然而，寻找这些化合物的高效节能合成路线和稳定机制仍然具有挑战性。分子二氮的直接合成需要克服较大的活化障碍，反应产物具有内在的不均匀性。

该文中，研究人员报道了在压力高于45GPa的金刚石砧槽中，通过激光加热叠氮化钾（KN₃）合成平面N62六嗪二阴离子，并在K2N6中稳定。由此产生的K2N6呈现出金属光泽，在20GPa以下保持亚稳态。利用同步辐射X射线衍射和拉曼光谱对该材料进行了鉴定，其结果与理论预测的K2N6的结构、振动和电子性质非常一致。这里描述的N62环很可能存在于其他通过压力稳定的高能量密度材料中。在30GPa以下，生成了一种含有分子式为K3（N2）4化合物的不同寻常的N20.75。

附：英文原文

Title: Stabilization of hexazine rings in potassium polynitride at high pressure

Author: Wang, Yu, Bykov, Maxim, Chepkasov, Ilya, Samtsevich, Artem, Bykova, Elena, Zhang, Xiao, Jiang, Shu-qing, Greenberg, Eran, Chariton, Stella, Prakapenka, Vitali B., Oganov, Artem R., Goncharov, Alexander F.

Issue&Volume: 2022-04-21

Abstract: Polynitrogen molecules are attractive for high-energy-density materials due to energy stored in nitrogen–nitrogen bonds; however, it remains challenging to find energy-efficient synthetic routes and stabilization mechanisms for these compounds. Direct synthesis from molecular dinitrogen requires overcoming large activation barriers and the reaction products are prone to inherent inhomogeneity. Here we report the synthesis of planar N62 hexazine dianions, stabilized in K2N6, from potassium azide (KN3) on laser heating in a diamond anvil cell at pressures above 45GPa. The resulting K2N6, which exhibits a metallic lustre, remains metastable down to 20GPa. Synchrotron X-ray diffraction and Raman spectroscopy were used to identify this material, through good agreement with the theoretically predicted structural, vibrational and electronic properties for K2N6. The N62 rings characterized here are likely to be present in other high-energy-density materials stabilized by pressure. Under 30GPa, an unusual N20.75-containing compound with the formula K3(N2)4 was formed instead.

DOI: 10.1038/s41557-022-00925-0

Source: https://www.nature.com/articles/s41557-022-00925-0