Synthesis and Properties of Quinoidal Fluorenofluorenes

The synthesis and
optoelectronic properties of 24 π-electron,
formally antiaromatic fluoreno­[3,2-b]­fluorene and
fluoreno­[4,3-c]­fluorene (FF), are presented. The
solid-state structure of [4,3-c]­FF along with computationally
analogous molecules shows that the outer rings are aromatic while
the central four rings possess a bond-localized 2,6-naphthoquinodimethane
motif. The antiaromaticity and biradical character of the FFs is assessed
computationally, the results of which indicate the dominance of the
closed-shell ground state for these molecules.