Theoretical Study of the Substituent and Nitrogen Number Effects on the Uranium Binding Selectivity of Crown Ethers

Abstract

The  compounds,  [UO₂(dibenzo-18-crown-6)]²⁺  and  [UO₂(18-crown-6)]²⁺,  as  well  as  their related complexes: numerous disubstituted dibenzo-18-crown-6 and azacrown complexes are studied  using  density  functional  theory  (DFT).  Quasi-relativistic  effective  core  potentials developed in the Stuttgart and Dresden groups was used together with the accompanying basis set for  uranium  and  DZP  basis  set  was used  for crown ether  atoms.  The  effects  of  substituent  and nitrogen number  on the binding selectivity were  discussed  in  term  of  the  structural  parameter,  atomic  charge  and interaction energy, thermodynamic parameters, and charge transfer. The electron donating substituents increase the capability of dibenzo-18-crown-6 toward UO₂²⁺ ion. In contrast, the electron withdrawing substituents have the opposite effect. It clearly shows that UO₂²⁺ prefers N donor recognition. For the systems involved, the result shows that the hexaaza-18-crown-6 exhibits the largest metal interaction capability to UO₂²⁺ ion. The calculated results are in a good agreement with the experimental values.