Widely used as a key intermediate in the synthesis of fluorescent dyes, particularly rhodamine derivatives. Its rigid spirocyclic structure enhances photostability and quantum yield in the resulting dyes. Commonly employed in the development of fluorescent probes for biological imaging, where its chlorine substituents allow for further functionalization and tuning of emission properties. Also utilized in sensor technologies for detecting metal ions and pH changes in environmental and clinical samples. Its dioxide form contributes to improved solubility and stability in aqueous media, making it suitable for applications in live-cell imaging and diagnostic assays.