Kinetically Blocked Stable 5,6:12,13-Dibenzozethrene: A Laterally π‑Extended Zethrene with Enhanced Diradical Character

Although
the ground-state and physical properties of zethrene and
recently invented 1,2:8,9-dibenzozethrene have been well studied,
the other dibenzozethrene isomer, i.e., 5,6:12,13-dibenzozethrene,
remained unexplored. A short synthetic route to a kinetically blocked
stable 5,6:12,13-dibenzozethrene derivative 5 is presented.
The ground state is found to be open-shell singlet experimentally,
and the theoretical y0 was enhanced to
0.414, which corroborates nicely with the experimental and theoretical
singlet–triplet energy gap.