Used as a key intermediate in the synthesis of fluorescent dyes, particularly in the production of pH-sensitive and metal-ion-responsive probes. Its rigid spirocyclic structure enhances photostability and quantum yield, making it valuable in bioimaging and environmental sensing applications. Commonly employed in the development of chemosensors for detecting trace metals in aqueous systems due to its selective binding and strong emission properties. Also utilized in solid-state fluorescent materials for optoelectronic devices and security inks.