From Rings to Properties: Understanding the Effect of Annelation on Pyrene.

Pyrene is a central building block in organic materials chemistry, valued for its rigid aromatic core, high fluorescence, and rich capacity for structural elaboration. However, the fundamental relationship between its annelation pattern and resulting electronic properties remains underexplored. In this work, we present a comprehensive computational study of 4,766 pyrene-based polybenzenoid hydrocarbons from the COMPAS-3D data set. By systematically categorizing annelation patterns based on the positions of fused benzene rings, we uncover clear structure-property trends governing key electronic parameters, including molecular orbital energies and oxidation and reduction potentials. We find that annelations at different positions exert different effects, which combine additively, and that these trends correlate with the distribution of fixed versus migrating Clar sextets. We further show that extended linear annelation can dominate electronic behavior, superseding local pyrene effects. Additionally, we evaluate the effect of torsional strain, revealing a clear link between annelation patterns and thermodynamic molecular destabilization. These insights provide a framework for the rational design of functional pyrene-based molecules.