Density functional theory investigation of the coordination of Zn(II)-tetraphenylporphyrin with 1,2,3-triazole ligands

Abstract

In this paper, we report density functional theory (DFT) studies to fully understand the coordination interactions between 1,4-disubstituted 1,2,3-triazole derivatives and the metal center of Zn(II)-porphyrins. Coordination through the most electron-rich N3 atom of the triazole heterocycle is more favorable. However, the energy difference between the N2- and N3-coordinated isomers is moderate and the less stable is likely also present in the solution. The binding of 1,4-disubstituted 1,2,3-triazole ligands to oxidized and reduced Zn(II)-porphyrins has been also investigated. Upon reduction, the binding interactions are extremely weak and the formation of the complex is not favorable anymore. In contrast, the binding energy is considerably increased upon oxidation of the Zn(II)-porphyrin moiety thus leading to more stable complexes. The calculations fully support experimental findings and explain the differences observed for the redox potentials of complexed and uncomplexed Zn(II)-porphyrin residues.