A new rhodamine based colorimetric 'off-on' fluorescence sensor selective for Pd2+ along with the first bound X-ray crystal structure.

A new fluorescence rhodamine derivative bearing an 8-aminoquinoline moiety has been designed and synthesized for selective sensing of Pd(2+) in the presence of other competing metal ions in aqueous media. Pd(2+) induced spirolactam ring opening of rhodamine is confirmed for the first time by the X-ray crystal structure of the bound Pd(2+)-complex.