Coordination-dependent electrochemical nitrite sensing in Zn(II) Schiff base complexes: Experimental–computational insights

In this work, the influence of coordination environment on the electrochemical sensing performance of Zn(II) Schiff base complexes toward nitrite detection is investigated. Two complexes, Zn(SB1)I₂ and Zn(SB2)I₂, with different coordination geometries were synthesized and used to modify screen-printed carbon electrodes. Zn(SB1)I₂ exhibited superior sensing performance, with a wide linear range up to 5 mM, a detection limit of 1.82 μM, and good repeatability, relative standard deviation (RSD: 5.26%), whereas Zn(SB2)I₂ showed a weaker response. This difference highlights the critical role of coordination structure in controlling sensor behavior. Computational studies, including density functional theory (DFT), molecular electrostatic potential (MEP), and frontier molecular orbital (FMO) analysis, suggest that nitrite interaction at the Zn center induces electronic redistribution and facilitates charge transfer, more effectively in Zn(SB1)I₂. These findings demonstrate that the coordination environment of the metal center governs sensing performance, providing insight for the rational design of electrochemical sensors.