New application of a known molecule: rhodamine B 8-hydroxy-2-quinolinecarboxaldehyde Schiff base as a colorimetric and fluorescent "off-on" probe for copper (II).

Rhodamine B 8-hydroxy-2-quinolinecarboxaldehyde Schiff base (1) has been investigated as a colorimetric and fluorescent "off-on" probe for the recognition of Cu(2+) in aqueous solution. Probe 1 was synthesized by condensation of rhodamine B hydrazide and 8-hydroxy-2-quinolinecarboxaldehyde, which exhibited good selectivity for Cu(2+) among a range of biologically and environmentally important metal ions. The Cu(2+) recognition event undergoes a Cu(2+) promoted hydrolysis of probe 1 to release rhodamine B and the recognition process is barely interfered by other coexisting metal ions.