Charge Transfer Emission of T‑Shaped π‑Conjugated Molecules: Impact of Quinoid Character on the Excited State Properties

We investigate the impact of quinoid character of a π-conjugation system on the emission properties of T-shaped cross-conjugated molecules. Three π-conjugated systems with different quinoid nature including benzothiophene, 2-phenylthiophene, and 2-phenylthieno­[3,2-<i>b</i>]­thiophene were connected orthogonally to a π-conjugated bis­(phenylethynyl)­arylene with an acid responsive <i>N</i>-methylbenzimidazole junction. The enhancement of quinoid character of a vertical π-system effectively suppressed the twisted intramolecular charge transfer (TICT) emission, leading to a more planar ICT state with enhanced emission intensity as well as a shortened Stokes shift