A bifunctional rhodamine derivative as chemosensor for recognizing Cu²⁺ and Hg²⁺ ions via different spectra

A new simple bifunctional chemosensor 1 based on rhodamine was synthesized by hydrazide and formylformic acid, which could detect Cu²⁺ and Hg²⁺ via different detecting methods in CH₃CN-HEPES buffer solution (20 mmol/L, pH 7.4) (1:9, v/v) respectively. When sensor 1 bound with Cu²⁺, it showed a colorimetric change, while a selective enhancement in fluorescence occurred upon 1 binding with Hg²⁺, resulting from the spirolatam-ring opening process. The binding modes of 1 with Cu²⁺ and Hg²⁺ were investigated based on UV, fluorescence change, ESI-Mass and Job's Plot data. Moreover, sensor 1 could selectively detect target ion in a mixed solution of Cu²⁺ and Hg²⁺, and the two metal ions do not interfere with each other in the process of detecting Cu²⁺ or Hg²⁺ with 1.