Employing the “off-on” switching of the spirocyclic moiety in rhodamine B derivatives, two highly selective and sensitive probes for Fe³⁺ were prepared and confirmed by X-ray crystallography. An obvious fluorescent enhancement was observed in the presence of Fe³⁺, accompanied by significant color changes, which can be used for “naked-eye” detection. Moreover, confocal laser scanning microscopy experiments have proven that the probes were successfully used for fluorescence imaging in HepG2 cells.