Spirolactamized benzothiazole-substituted N,N-diethylrhodol: a new platform to construct ratiometric fluorescent probes

A new rhodol dye 3 with an ESIPT unit has been successfully developed, which can serve as a convenient and universal platform for developing ratiometric sensing systems based on the unique spirocyclic ring-opening process. As a model platform, rhodol 3 hydrazide (4) was prepared and it showed ratiometric response toward Cu2+.