Synthesis and Characterizations of Dibenzo‐Fused Perioctacene

Abstract Dibenzoperioctacene (DBPO) with extended zigzag edges was synthesized and unambiguously characterized by a combination of nuclear magnetic resonance (NMR), mass spectrometry, and single‐crystal X‐ray diffraction analysis. Variable‐temperature (VT) NMR analysis indicated the closed‐shell character of DBPO, yet the bond lengths in the single‐crystal structure of DBPO aligned more closely with those of open‐shell teranthene than closed‐shell bisanthene. Spin‐unrestricted density functional theory (DFT) calculations using various methods supported that ground state of DBPO might be on the borderline between closed‐ and open‐shell singlet states, with a large singlet‐triplet energy gap ( ΔE ST ), consistent with the VT NMR and bond‐length analyses. UV/Vis‐near infrared (NIR) absorption spectrum showed the longest‐wavelength peak at 905 nm, marking the NIR optical properties of DBPO. DBPO exhibited a tendency to react with atmospheric oxygen, which additionally hinted at its possible open‐shell character. Furthermore, the oxidized species of non‐fluorescent DBPO exhibited strong emission at 820 and 915 nm.