Non-stoichiometric quinhydrone-type CT complexes: Mixed crystals of triptycenequinone and 1,4-dimethoxytriptycene with characteristic color caused by local CT interaction

1,4-Dimethoxytriptycene (diMeO-TP) and triptycenequinone (TPQ), non-planar donor and acceptor molecules, respectively, were found to form two types of mixed crystals with limited solubility, i.e., (diMeO-TP)x(TPQ)1−x with x = ca.0.25 and (diMeO-TP)x(TPQ)1−x with x = ca.0.97. Crystal structures of the mixed crystals suggested that their characteristic colors, which are different from those of TPQ (yellow) and diMeO-TP (colorless), are caused by local CT interactions between 1,4-benzoquinone and 1,4-dimethoxybenzene moieties in the crystals. The present mixed crystals can be regarded as non-stoichiometric quinhydrone-type CT complexes similar to that formed by TPQ and TPHQ (triptycenehydroquinone).