<i>Peri</i>-pentacene and <i>Peri</i>-hexacene Diradicaloids
Ya Zou, Liuying Jiao, Yi Han, Longbin Ren, Qifeng Zhou, Jishan Wu
Abstract
Peri -acenes are valuable models for zigzag-edged graphene nanoribbons, but their synthesis poses significant challenges. In this study, stable derivatives of peri -pentacene ( Peri-P ) and peri -hexacene ( Peri-H ) were synthesized. Through kinetic blocking and a synergistic captodative effect, both compounds displayed remarkable stability under ambient air and light conditions. They show significant diradical character ( y 0 ), with y 0 = 75.4% for Peri-P and y 0 = 90.7% for Peri-H, alongside narrow singlet–triplet energy gaps of −1.68 ± 0.04 and −1.28 ± 0.02 kcal/mol, respectively. The structure of Peri-H was confirmed by X-ray crystallography, with bond-length analysis and theoretical calculations indicating a dominant structure featuring five aromatic sextet rings. Their optical and electrochemical properties were also studied and compared to those of smaller peri -acenes.