DFT calculations on the electronic and geometrical structure of 18-crown-6 complexes with Ag +, Hg 2+, Ag 0, Hg +, Hg 0, AgNO 3, and HgX 2 (X=Cl, Br, and I)

Abstract

Density functional theory is used for molecular simulation of the electronic and geometrical structure of 18-crown-6, its complexes with Ag +, Hg 2+, Ag 0, Hg +, Hg 0, AgNO 3, and HgX 2 (X=Cl, Br, and I). Ab initio MP2/6-31G ∗ calculations are performed for the two main conformations of the free crown ether and for anion-free complexes. The complex formation energies are analysed in terms of various contributions including Pauli and electrostatic repulsion and orbital interactions according to the Morokuma scheme. It is found that the Hg 2+ ion is most strongly bound to the crown ether; silver and mercury ions in the 18-crown-6 cavity can capture an electron, and neutral 18-crown-6 complex of silver can be bound through van der Waals-type interactions. The stability of metal complexes with supporting anionic ligands is determined not only by the cation charge, but also by the type of the ligand.