Asymmetric Pyrrolopyrrole aza-BODIPYs: Intramolecular Charge Transfer and Redshifts of the Optical Properties

Abstract Asymmetric pyrrolopyrrole aza-BODIPYs (PPABs) bearing two different aza-aromatic ring units were synthesized from diketopyrrolopyrrole (DPP) and the corresponding aza-arylamines by stepwise Schiff base-forming reactions via a DPP-aza-BODIPY hybrid, named half-PPAB. Due to intramolecular charge transfer interactions, one of the asymmetric PPABs exhibited notable Stokes shifts compared to symmetric PPABs, resulting in the far-red fluorescence.