Exploring the Impact of Topological Variations on the Stability of the Ground Singlet and Lowest-Lying Triplet States of Catacondensed Hexabenzenoids

Abstract

Polycyclic aromatic hydrocarbons (PAH) such as tetracenes, pentacenes, hexacenes, and some higher acenes play a central role in organic electronics due to their unique electronic properties. The impact of topological variations on the relative stability of PAH isomers in different electronic states is poorly understood, with limited insights into how Clar π-sextets and topological features such as bay, cove, fjord, and K-regions influence stability in their ground singlet (S0) and lowest-lying triplet (T1) states. In this work, density functional theory calculations of the S0 and T1 states of the 37 catacondensed hexabenzenoids are performed. A multivariate linear regression model with relative energy as the dependent variable and a series of topological parameters as the independent variables is used to quantify the effect of topology in the relative stability of the catacondensed hexabenzenoids. Analysis shows that, in S0, stability is enhanced by an increase in the number of Clar π-sextets and K-regions and decreased by the presence of coves and fjords. In T1, the main stabilizing factors are the number of Clar π-sextets and the number of rings involved in the antiaromatic region, whereas topological regions such as K-edges, bays, coves, or fjords are destabilizing