Accurate Heats of Formation for Polycyclic Aromatic Hydrocarbons: A High-Level Ab Initio Perspective

Polycyclic aromatic hydrocarbons (PAHs) are key reference materials for the validation and parameterization of computationally cost-effective procedures such as density functional theory (DFT), semiempirical molecular orbital theory, mechanics. We obtain accurate heats formation (ΔHf,298) 20 PAHs with up to 18 carbon atoms by means explicitly correlated W1-F12 thermochemical procedure. The obtained via atomization reactions quasi-isodesmic involving CH4, C2H4, C6H6 which experimental ΔHf,298 values available from active tables (ATcT) network. show that large PAHs, differences between increase size system range 1.7 (C7H8) 8.9 (chrysene, C18H12) kJ mol–1. This suggests should be used caution obtaining medium-sized systems even when highly (such theory) used. For eight PAH compounds (toluene, indene, acenaphthylene, biphenyl, diphenylmethane, anthracene, pyrene, chrysene), our best theoretical agree within ∼1 mol–1; six additional (indane, naphthalene, biphenylene, acenaphthene, phenanthrene, m-terphenyl), agreement experiment is good deviations ranging 2 4 However, four (p-terphenyl, fluorene, pyracene, pyracyclene), suggest revised significant amounts 6.5 24.4