Schiff Base Ligands for Electrochemical Detection of Cd ²⁺ in Water Samples: Performance and Theoretical Investigations

Two ethylenediamine‐based Schiff base ligands (L3 and L4) were designed and synthesized as electroactive materials for the selective electrochemical detection of Cd ²⁺ . The structural modification of the molecular scaffold was investigated to establish a relationship between molecular structure, electronic properties, and sensing performance. The ligands were characterized by ¹ H NMR, Fourier transform infrared, UV–Vis spectroscopy, and density functional theory (DFT) calculations, which confirmed their successful synthesis and favorable electronic properties. Electrochemical characterization by cyclic voltammetry and electrochemical impedance spectroscopy revealed enhanced charge–transfer efficiency at L3 and L4 modified glassy carbon electrodes. Differential pulse voltammetry demonstrated excellent Cd ²⁺ sensing performance, with detection limits of 21 nmol.L ⁻¹ for L3/GCE and 17 nmol.L ⁻¹ for L4/GCE over a wide linear range of 1−240 nmol.L ⁻¹ . L4/GCE exhibited superior performance, attributed to its favorable electronic properties and enhanced charge transfer, consistent with DFT results. Moreover, L4/GCE achieved recovery rates close to 100% in real water samples. These findings demonstrate the novelty of the proposed Schiff base functionalization strategy and highlight L4/GCE as a promising sensitive and selective platform for Cd ²⁺ monitoring.