Visible colorimetric sensing of Zn2+ and CN− by diaminomaleonitrile derived Schiff’s base and its applications to pharmaceutical and food sample analysis

Abstract

A newly designed diaminomaleonitrile derived schiff’s base probe L was synthesized by reacting 2,3-diaminomaleonitrile with 3,5-tert-butyl-2-hydroxybenzaldehyde and structurally characterized by various spectroscopic techniques. The sensing ability of probe L was studied with various cations and anions by visual and UV visible techniques. It reveals that L is selectively interacting with Zn2+ and CN− ions resulted in distinct colour changes from yellow to grey and colourless respectively. The probe L exhibits 1:1 complex formation with these analytes and it can work in the pH range of 8–10 and 5–8 with Zn2+ and CN− respectively without interfering with other competing ions. The spectral response was used estimate the limit of detection of Zn2+ and CN− and it is found to be 0.58 μM and 0.33 μM respectively. Further, the probe L was applied for the quantification of analytes in real samples. The binding mechanism of L with Zn2+ was characterized by using 1H NMR, ESI mass, and DFT analysis. The frontier molecular orbital analysis (FMO) analysis reveals that that Zn2+ and CN− are exhibiting metal-to-ligand charge transfer (MLCT) and internal charge transitions (ICT) respectively. Overall, probe L demonstrates a promising and potential for the detection of Zn2+ and CN− in the semi-aqueous phase.