DFT Theoretical Description of Cu(I)/Cu(II) Interactions with Various Ligand Fields

 

Matěj Pavelkaa, and Jaroslav V. Burdaa

 

aDepartment of Chemical Physics and Optics, Faculty of Mathematics and Physics,Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic

 

Both monovalent and divalent copper cations are essential for an occurrence of many processes in bioorganisms. They are present in active centers in number of redox enzymes, for example in so called blue proteins. Hence, quantum chemical investigation of copper interaction with key ligands is useful and important. This presentation summarizes our studies of Cu+ and Cu2+ cations in variable sulphur-ammonium-water ligand fields. At first, structures were optimized at DFT level using B3PW91 functional. Double-z basis set with additional diffusion and polarization functions was used. Inner electrons of Cu and S atoms were described by effective pseudopotentials. Stabilization energies and other electronic properties were calculated with B3LYP functional with more accurate augmented triple-zeta basis set.

It was found that the optimal Cu(I) coordination involves two directly bonded solvent molecules for ammonium-water ligand field. If SH2 ligand molecules are present, Cu+ cation tends to 3 or even 4 coordination. The Cu2+ cation prefers four and five coordinated complexes for all types of ligand fields. If strength of metal-ligand dative bonds is compared, the following order would be predicted: ammonium, water, and sulphur. Therefore NH3 molecules always stay in the first solvation shell in mixed compounds. Our studies also contained Natural Population Analysis that gives further support of the calculated results and enables detailed insight to the calculated systems. The most stable structures correlate with the highest donations of ligand electron densities to copper atom.