Synthesis and Properties of Rubicene‐Based Aromatic π‐Conjugated Compounds as Five‐Membered Ring Embedded Planar Nanographenes

Abstract

AbstractPolycyclic aromatic hydrocarbons consisting of two or three rubicene substructures were designed as π‐conjugated compounds embedding five‐membered rings. The target compounds with t‐butyl groups were synthesized by the Scholl reaction of precursors consisting of 9,10‐diphenylanthracene units, even though a partially precyclized precursor was required for the synthesis of the trimer. These compounds were isolated as stable and dark blue solids. Single‐crystal X‐ray analysis and DFT calculations revealed the planar aromatic framework of these compounds. In the electronic spectra, the absorption and emission bands were considerably red‐shifted compared with those of the reference rubicene compound. In particular, the emission band of the trimer extended to the near‐IR region while retaining the emissive property. The narrowed HOMO‐LUMO gap with the extension of the π‐conjugation was confirmed by cyclic voltammetry and DFT calculations.