Synthesis, Characterization and DFT analysis of Aryl-substituted Carbohydrazides based Chromoflourescent Sensor for detection of Heavy metal ions.

Aryl-substituted carbohydrazide-based molecules (B1-B5) were rationally designed and synthesized as potential chemosensors for detection of environmentally significant metal ions in excellent yield 80-94%. Their sensing capability was initially investigated via colorimetric studies, which showed distinct visible color changes upon interaction with Cu²⁺, Hg²⁺, and Zn²⁺ ions, associating their potential as selective colorimetric probes. UV-Vis absorption spectroscopy revealed further confirmation, exhibited bathochromic and hyperchromic shifts in absorption spectra which corresponding to n→π* transitions of the CH=N group. These shifts indicative of charge transfer complex formation upon metal ion binding. Among these tested receptors, B1 displayed strong selectivity towards Cu2+, B2 responsive to both Hg2+ and Cu2+, B3 to Cu²⁺, B4 to Zn²⁺, and B5 to Hg²⁺ metal ions. DFT study (FMO, DOS, MEP and global reactivity parameters) supported the experimental results that revealed favorable HOMO-LUMO energy gaps, charge distributions, and reactive binding sites. Our integrated experimental and theoretical research approach validates novel Aryl-substituted carbohydrazides (B1-B5) as efficient, cost effective and reliable chemosensors for selective heavy metal ions detection.