Investigation of the stability of azacrown complexes with some transition metal ions

Abstract

The separation of metal ions from nuclear waste is an important issue in the nuclear industry. Cyclic chemical compounds including ether groups are called crown ethers. These compounds strongly bind to certain cations, forming complexes. Successive oxygen substitution with nitrogen leads to form new structures called Azacrown. In this work, quantum mechanical calculations based on density functional theory (DFT) has been used to investigate the stability of complexes formed between various Azacrowns and selective transition metals (M) ( M= Mn2+, Fe2+ , and Co2+). The results showed that binding energies (ΔE) for titled metals are enhanced by increasing the number of replaced oxygen atoms in crowns structure. For example, the fully substituted Azacrown complexes of Mn2+, Fe2+ , and Co2+ are about 16.8, 22.4, and 37.2 kcal/mol more stable than corresponded crown ethers complexes, respectively. Analogous trends were found for ΔH and ΔG of complexation reactions.

Keywords

• azacrown
• transition metal
• complexes
• density functional theory
• quantum theory of atoms in molecules