Synthesis and characterization of the Na2CdEDTA complex, and density functional theory (DFT) study of EDTA species

Abstract

Cadmium, a toxic environmental contaminant, accumulates in the food chain, causing oxidative stress and health risks, necessitating detection methods. Our study employs Density Functional Theory (DFT) to investigate the electronic structure and reactivity of EDTA microspecies, focusing on their highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) using ORCA 5.0 and the B3LYP functional. Geometric optimizations utilized the def2-SVP basis set, and the calculations incorporated advanced convergence techniques to ensure accuracy. The results revealed ten distinct EDTA microspecies, each exhibiting unique electronic properties. Notably, the -4YO microspecies predominates at pH levels of 7 or higher, characterized by a high HOMO energy and significant electron delocalization. Reactivity assessments demonstrated varying stability and chemical behavior across the microspecies, with the -4YO showing a propensity for rapid reactions due to electrostatic repulsion among negative charges. The study also synthesized the Na₂CdEDTA complex, characterized by UV–Vis, FT-IR, and XRD techniques. XRD confirmed a distinct crystalline structure, while FT-IR and UV–Vis analyses indicated coordination between Cd²⁺ ions and EDTA's carboxyl groups. The findings emphasize the significant influence of pH on EDTA's chelating efficiency, highlighting its potential in applications like water purification and medical treatment. This work provides a comprehensive understanding of EDTA's electronic structure, reactivity, and complexation behavior with metal ions.