Compressional Behavior of Naphthalene (C ₁₀ H ₈ ) and Anthracene (C ₁₄ H ₁₀ ) 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: <i>V</i> ₀ = 182.2(2) ų, <i>K</i> ₀ = 8.4(10) GPa, and <i>K</i>' = 5.5(6) for naphthalene, and <i>V</i> ₀ = 238.0(2) ų, <i>K</i> ₀ = 8.4(5) GPa, and <i>K</i>' = 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.