Manganese(III) Complexes of Porphyrin-based Ligand: Synthesis, DFT Study and Catalytic Application

Four new Mn(III) porphyrin complexes with 1,2-diaminoethane were synthesized, with the general formula [MnIII(TEHPP)X(dae)], where TEHPP is 5,10,15,20-tetra(3-ethoxy-4-hydroxyphenyl)porphine, X represents Cl–, Br–, NCS– or N3– and ‘dae’ is 1,2-diaminoethane. These complexes were characterized with ultraviolet-visible (UV-visible) spectroscopy, Fourier transform-infrared (FT-IR), elemental analyses, magnetic susceptibility measurements and conductivity measurements. The synthesized novel Mn(III) porphyrins exhibit catalytic activity in the oxidation of aromatic alcohols to aldehydes. The catalytic performance of these complexes was evaluated for the oxidation of benzyl alcohol derivative to corresponding aldehyde at room temperature (30 ºC) using oxidants such as NaIO4, H2O2 and NaOCl. Density functional theory (DFT) calculations were also conducted to optimize the complex structures and HOMO–LUMO energies were determined using NBO analysis at the same theoretical level.