1,6-Diazapyrene: A Novel, Well-Defined, Small-Size Prototype System for Nitrogen-Containing PAHs

The quest for nitrogen-doped (N-doped) polycyclic aromatic hydrocarbons (PAHs) requires well-defined prototype systems to understand the relationship between the structure and the resulting photophysical and photochemical properties. To this end, a novel, simple, and small compound, 1,6-diazapyrene, was synthesized. In-depth analysis, employing optical spectroscopy and (time-dependent) density functional theory, (TD-)DFT, elucidates the optical excitations on the basis of MO symmetry, energy, and topology considerations; the study further unveils the photophysical and photochemical deactivation kinetics after photoexcitation, revealing extreme changes against pyrene as well as against the well-known 2,7-diazapyrene isomer. The high sensitivity of the aza-substitution position to generate such changes is considered as highly relevant for the targeted design of N-doped PAHs in general.