Synthesis of Functional Organic Fluorescent Dyes for Advanced Devices and Molecular Imaging

Organic fluorescent dyes are essential to optoelectronic devices and molecular imaging, but practical use demands simultaneous optimization of absorption/emission, quantum yield, environmental responsiveness, photostability, processability, and biocompatibility. This account outlines an integrated design strategy that combines elucidation of excited-state structures and deactivation pathways in π-electronic frameworks, theoretical prediction of emission behavior, and modern synthetic functionalization. Using robust π-platforms with finely tuned donor/acceptor motifs and conformational control, minimalist dyes and liquid-crystalline materials were developed with high matrix compatibility and strong application performance. Solvatochromic fluorophores were engineered to maintain high quantum yields while exhibiting large, continuous polarity-dependent color shifts, enabling sensitive mapping of membrane microenvironments and low-toxicity long-term live-cell imaging. Further advances include near-infrared-excitable two-photon dyes for deep-tissue observation and probes that selectively detect trihalomethanes via coupled fluorescence signaling and photodecomposition. For aggregation-induced emission (AIE), catalytic C-N cross-coupling provided access to highly twisted amino-substituted polycyclic aromatics, yielding bright, viscosity-responsive AIEgens. Mechanistic studies established a guiding principle: AIE can be rationally created by designing efficient solution-phase deactivation through conical-intersection access, rather than relying solely on rotational restriction.