Synthesis of Dibenzo[h,t]rubicene through Its Internally Dimethoxy-Substituted Precursor

Dibenzo[h,t]rubicene was synthesized from 1,5-dichloroanthraquinone via an internally dimethoxylated intermediate. In contrast to the planar conformation of rubicene, dibenzo[h,t]rubicene adopted a double-helicene-like structure due to the intramolecular steric repulsion around the fused benzene-rings. Theoretical calculation suggests that the helical inversion occurs frequently with an inversion barrier of 4.8 kcal mol−1. The HOMO–LUMO gap of dibenzo[h,t]rubicene is smaller than that of rubicene, resulting in its red-shifted absorption tailing to 690 nm. Dibenzo[h,t]rubicene was synthesized from 1,5-dichloroanthraquinone via an internally dimethoxylated intermediate. In contrast to the planar conformation of rubicene, dibenzo[h,t]rubicene adopted a double-helicene-like structure due to the intramolecular steric repulsion around the fused benzene-rings. The HOMO–LUMO gap of dibenzo[h,t]rubicene is smaller than that of rubicene, resulting in its red-shifted absorption tailing to 690 nm.