A Fluorescent Sensor for Trivalent Metal Ions and Colorimetric Sensor for Cu 2+ Based on a Novel Ferrocenyl Schiff Base Derivative

A novel fluorescent sensor ferrocenyl salicylaldehyde Schiff base derivative SF-Fc was designed, synthesized, and characterized by nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), and SC-XRD spectroscopic analyses. The sensor was highly selective to trivalent ions Al³⁺, Cr³⁺, and Fe³⁺ over other monovalent or divalent ions and showed fluorescence enhancement towards trivalent metal ions (Al³⁺, Cr³⁺, Fe³⁺) in acetonitrile (pH 6). Detection limits of probe SF-Fc for Al³⁺, Cr³⁺, and Fe³⁺ were 1.2 × 10^-7 mol/L, 2.4 × 10^-7 mol/L, and 4.9 × 10^-7 mol/L, respectively. In addition, the sensor exhibited an obvious color change in the presence of Cu²⁺ in acetonitrile solution, indicating a direct colorimetric naked-eye detection of Cu²⁺ without requiring instrumental assistance. Moreover, the probe SF-Fc successfully detected trivalent metal ions in actual water samples, with satisfactory recovery rates (88.7%-108.9%) and relative standard deviation (RSD) values (0.34%-2.91%).