Tetra-benzimidazoles flanking divinyl-phenothiazine: AIEgens as aza-Michael acceptors in concentration-tuned responses to biogenic amine vapors

Tetra-benzimidazole rotors flanking a divinyl-phenothiazine stator are realized as red AIEgens and newly identified as efficient aza-Michael acceptors for the identification of biogenic amine vapors. Weakly red-emissive solids display a blue-shifted turn-on emission by rapid aza-Michael addition and simultaneous reverse Knoevenagel reactions. Concentration variation imposes better crystallinity and facilitates radiative decay, offering distinct emissions.