Rhodamine 6G hydrazone bearing pyrrole unit: Ratiometric and selective fluorescent sensor for Cu2+ based on two different approaches

A new rhodamine-based derivative bearing pyrrole unit, R1 was synthesized as a dual-mode Cu2+-selective sensor via the rhodamine ring-opening approach and ratiometric displacement. A colorimetric and “off-on” signal for Cu2+ through rhodamine ring opening in R1 and ratiometric fluorescent signal output when Cu2+ displaces the bound Cd2+ in the R1-Cd2+ complex can be observed. The application of fluorescent R1 to biological imaging was also demonstrated.