Synthesis and Electronic Properties of Extended, Fused-Ring Aromatic Systems Containing Multiple Pentalene Units

A series of elongated dibenzopentalenes were synthesized via a Pd-catalyzed cyclization followed by an Fe-mediated cyclodehydrogenation. Structural geometries varying from linear to extremely bent are shown to drastically influence solubility properties as well as reduction potentials. Comparisons are made to monopentalenes and related diindenoindacenes. UV-vis absorption spectra and cyclic voltammetry measurements indicate a strong modulation of the electronic structure of these compounds mediated by the strength of interactions between pentalene centers.