Dual-state emission: the compatible art of substantial rigidity and twisting conformation within a single molecule

Dual-state emission (DSE) is an emerging phenomenon in which organic molecules exhibit bright emission in both dilute solution and solid states. This nascent concept replenishes the knowledge in photophysical areas and practical applications connected to the mono-state emission effect. Recently, the molecular blueprints of dual-state emissive luminogens (DSEgens) have boomed and advanced widespread realms ranging from molecular bioimaging to optoelectronic devices. However, a systematic survey on the structural features and working principles of DSEgens is rare to date. Herein, this collective review highlights compatibility oriented creations of intramolecular π-conjugated rigidity and twisted conformation in constructing efficient DSEgens, based on selected precursor skeletons. Simultaneously, we perform an in-depth analysis of the correlation between molecular configurations and emission properties of DSEgens, focusing on their emission efficiency and wavelength variability at the monomeric/aggregated level. In addition, preliminary applications of DSEgens are demonstrated, and the perspectives on their feature-based fundamentals and applications are shortly discussed.