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 y(0) was enhanced to 0.414, which corroborates nicely with the experimental and theoretical singlet-triplet energy gap.