Prediction of Spin Density, Baird?Antiaromaticity, and Singlet–Triplet Energy Gap in Triplet?State Polybenzenoid Systems from Simple Structural Motifs

Triplet-state aromaticity has been recently proposed as a strategy for designing functional organic electronic compounds, many of which are polycyclic aromatic systems. However, in cases, the nature triplet state cannot be easily predicted. Moreover, it is often unclear how specific structural manipulations affect properties excited-state compounds. Herein, relationship between structure polybenzenoid hydrocarbons (PBHs) and their spin-density distribution character first excited studied. Although direct link not immediately visible, classifying PBHs according to annulation sequence reveals regularities. Based on these, set guidelines defined qualitatively predict location spin paratropicity singlet–triplet energy gap larger PBHs, using only smaller tri- tetracyclic components, subsequently tested