How do molecular interactions affect fluorescence behavior of AIEgens in solution and aggregate states?

Molecular interactions are crucial in diverse fields of protein folding, material science, nanotechnology, and life origins. Although mounting experimental research controls luminescent behavior by adjusting molecular interactions in light-emitting materials, it remains elusive to correlate microscopic molecular interactions with macroscopic luminescent behavior directly. Here, we synthesized three red luminogens with subtle structural variation and investigated the influence of molecular interactions on their luminescent behavior in solution and aggregate states. Our results indicate that strong π-π and D-A interactions in both dilute solution (between luminogen and solvent molecules) and aggregate (between luminogens) states cause the redshift in emission, while weak interactions ({tie.g.}, Van der Waals, C-H⋯π, and C-H⋯F interactions) enhance the quantum yield. This work provides a thoughtful investigation into the complicated influence of various molecular interactions on luminescent behavior.