Annulated oxazolium anion-π + AIEgens.

A new class of anion-π + AIEgens based on ring-fused annulated oxazolium architectures is reported, which can be readily synthesized via a single-step dual C-H activation annulative π-extension (APEX) protocol from simple oxazolium salts. The crucial and decisive role of anion-π + interactions in their solid-state structural arrangement was analyzed to correlate their tunable AIE features and solid-state quantum yields.