Compressional Behavior of Naphthalene (C₁₀H₈) and Anthracene (C₁₄H₁₀) up to 50 GPa

In this study, we explored the behavior of naphthalene and anthracene under compression to ∼50 and ∼42 GPa, respectively, using synchrotron single-crystal X-ray diffraction (SCXRD) in diamond anvil cells. Both compounds demonstrate remarkable structural stability, with no phase transitions being observed. The equations of states were obtained with the following parameters: V0 = 182.2(2) Å3, K0 = 8.4(10) GPa, and K′ = 5.5(6) for naphthalene, and V0 = 238.0(2) Å3, K0 = 8.4(5) GPa, and K′ = 8.0(4) for anthracene. Theoretical calculations correctly reproduce experimental data and enable accurate localization of hydrogen atoms. The analysis of Hirshfeld surfaces for both naphthalene and anthracene suggests that the herringbone packing motif of the molecules, the limited contribution of stronger C···C interactions to intermolecular bonding, and the high flexibility of relatively weak H···H interactions allow a gradual compaction of their structures without phase transitions. Our research contributes to the understanding of the compressional mechanisms, bonding evolution, and structural stability of polyaromatic hydrocarbons under compression.本研究借助金刚石对顶砧（diamond anvil cells）装置中的同步辐射单晶X射线衍射（single-crystal X-ray diffraction, SCXRD）技术，分别探究了萘（naphthalene）与蒽（anthracene）在被压缩至约50 GPa和约42 GPa时的结构行为。两种化合物均表现出优异的结构稳定性，未观测到任何相变发生。本研究得到了两种物质的状态方程（equations of state），其参数如下：萘的状态方程参数为V₀=182.2(2) ų，K₀=8.4(10) GPa，K′=5.5(6)；蒽的状态方程参数为V₀=238.0(2) ų，K₀=8.4(5) GPa，K′=8.0(4)。理论计算结果可准确复现实验数据，并能实现氢原子位置的精准定位。对萘与蒽的赫希菲尔德表面（Hirshfeld surfaces）进行分析后发现，分子的人字堆积基元、较强的C···C相互作用对分子间键合的有限贡献，以及相对较弱的H···H相互作用所具备的高柔性，使得两种物质的结构可在不发生相变的前提下实现逐步致密化。本研究有助于加深学界对压缩条件下多环芳烃（polyaromatic hydrocarbons）的压缩机制、键合演化及结构稳定性的理解。