Ferrocene‐Based Schiff Base Chemosensor for the Detection of Cu ²⁺ Ions in Aqueous Media and Cell Imaging: Synthesis, Characterization, and Biomedical Applications

A novel Schiff base chemosensor derived from ferrocene (FSBCS) has been synthesized by condensation of ferrocene carboxaldehyde with pyridine‐4‐carbohydrazide for selective detection of Cu 2+ ions via dual colorimetric and fluorometric responses. A newly synthesized ferrocene‐based chemosensor offers highly sensitive Cu 2+ recognition and biological functionality, enabling simultaneous chemical sensing and cellular imaging. Structural elucidation was achieved using FTIR, HRMS, 1 H NMR, and 13 C NMR techniques. FSBCS displayed a rapid color transition from brown to orange‐red and pronounced spectral changes selectively in the presence of Cu 2+ ions. The analysis of the Job's plot, coupled with compelling evidence from mass spectrometry and FTIR spectroscopy, unequivocally confirmed a 1:1 binding stoichiometry between FSBCS and Cu 2+ ions. The complex formation between FSBCS and Cu 2+ was supported by DFT calculations with Gaussian 16, using the B3PW91 functional and the 6‐311+G(d,p) basis set for geometry optimization. The binding constant for the FSBCS–Cu 2+ complex was determined to be 3.49 × 10 4 . The chemosensor exhibited a detection limit of 4.59 × 10 −8 M and a quantification limit of 15.30 × 10 −8 M. In addition, FSBCS showed moderate antioxidant and antibacterial activities. Cytotoxicity studies in L929 cells confirmed good biocompatibility, whereas fluorescence imaging demonstrated efficient intracellular Cu 2+ detection, highlighting its potential for advanced bioanalytical applications.