Molecular Engineering of N–H-Type ESIPT Fluorophores Enabling Tunable Emission and ESIPT-AIE Integration

Abstract Systematic molecular engineering of benzothiazole-based excited-state intramolecular proton transfer (ESIPT) fluorophores is achieved through complementary modulation of the para substituent and proton-donating N site. While para-substituent variation enables continuous emission tuning within the conventional ESIPT framework, N-site acylation drives the evolution toward ESIPT–aggregation-induced emission (AIE) luminogens with large Stokes shifts and bright solid-state fluorescence. The established structure–photophysical relationships reveal the distinct roles of dual-site modulation and provide a rational design strategy for high-performance N–H-type ESIPT luminogens.