Co(II), Ni(II), and Zn(II) complexes based on new hybrid imine-pyrazole ligands: structural, spectroscopic, and electronic properties.

The present work reports the theoretical investigation of Co(II), Ni(II), and Zn(II) complexes containing Schiff bases (used as ligands) derived from the reaction of 2-hydroxy-1-naphthaldehyde with N-(2-aminoethyl) pyrazoles. The spectral analyses were carried out using infrared, Raman, and UV-Vis spectroscopy. Vibrational analyses were performed in order to investigate the mechanisms involving metal-ligand and intra-ligand vibrations and indicated the possibility of charge transfer related to the transitions n[Formula: see text]* and [Formula: see text]*. Structure optimizations and normal coordinate force field calculations were performed via the density functional theory (DFT) method at the HSE06/6-311G(d,p)/LanL2DZ level. A thorough analysis was also conducted regarding the nonlinear optical (NLO) properties and the natural bond orbital (NBO) of the complexes. The results show that these complexes have prospective application as materials for NLO. Furthermore, the NBO analysis confirms the coordination between the lone pair (LP) electrons of the donor atoms (O and N) and the metal acceptors. Finally, studies were conducted regarding the electronic properties of the complexes; among the properties investigated included the frontier molecular orbitals (FMO) and the molecular electrostatic potential (MEP), allowing to determine the energy gap and charge distribution.

Oxygen Reduction Reaction on a CuII Complex of 3,5-Diamino-1,2,4-triazole: A DFT Approach.

The high costs for producing catalysts for fuel cells combined with low efficiency in oxygen reduction make metal-organic complexes a promising alternative to noble-metal catalysts. The electrochemical activity of Cu-complex-based catalysts has been reported by many authors, but only a few works are devoted to theoretical studies. In this manuscript, we use density functional theory (DFT) calculations to investigate the oxygen reduction reaction (ORR) on a CuII complex of 3,5-diamino-1,2,4-triazole. The determining steps for the associative and dissociative mechanisms are the oxygen adsorption and the oxygen bond cleavage, respectively. The barrier for breaking the O-O bond in the dissociative mechanism was estimated at 0.7 eV.