Highly sensitive and selective turn-on fluorescent and chromogenic probe for Cu²⁺ and ClO⁻ based on a N-picolinyl rhodamine B-hydrazide derivative

A new rhodamine B-based dual-function chromo- and fluorogenic probe for Cu²⁺ and ClO⁻ has been designed, synthesized, and characterized. The probe comprises a spectroscopic unit of rhodamine B and a Cu²⁺-specific chelating unit of pyridinecarboxamide as well as a ClO⁻-specific reactive moiety of diacylhydrazine, and is a highly selective and extremely sensitive fluorescent and colorimetric sensor for Cu²⁺ and ClO⁻ in different pH conditions. Compared with the reported probes for Cu²⁺ or ClO⁻, this is the first chemosensor based on a small molecule that can detect both Cu²⁺ and ClO⁻, respectively, at 1 nM level.