Lactam node as a two-fold functional unit for achieving highly efficient and tunable dual-state emitters

Although custom design offers an opportunity for synthesizing molecules with desired emission characteristics, compared with single-state emission, underdeveloped methodologies pose a significant challenge to accessing and further tailoring of dual-state emission. Herein, we report 1,8-naphtholactam (Np) and its derivatives, which not only function as efficient dual-state emitters but also as excellent building blocks for tunable dual-state emitters. By adjusting the π-conjugated donor substituent, bright emission from cyan to red can be facilely tailored in both solution and the solid state, resulting in an approximative full-color emission. Structural analysis reveals that the lactam group of Np works as a two-fold functional unit, simultaneously guaranteeing molecular rigidity for solution emission and hydrogen-bond-modulated packing without detrimental long-range π-π stacking for solid emission. Theoretical calculations corroborate the experimental results and efficient red bioimaging of Human hepatocellular carcinomas (HepG2) cells is achieved after the incubation with an Np derivative. Therefore, our lactam substitution strategy is a new route suitable for achieving efficient and tunable dual-state emitters. We demonstrated a lactam node hydrogen-bonding strategy for achieving highly efficient and tunable dual-state emitters based on the 1,8-naphtholactam skeleton substituted with different π-electron donor moieties. [Display omitted] •Highly efficient and tunable dual-state emitters were constructed from the 1,8-naphtholactam (Np).•The lactam nodes act as two-fold functional units for their dual-state emission behavior.•Efficient red cell imaging was demonstrated after the incubation with Np derivative.