Realizing the Magnetostructural Correlation of a Highly Anisotropic Fe(III) Porphyrin Complex through <i>Ab Initio</i> Approaches

A mononuclear pentacoordinate Fe(III)-porphyrin-NCS complex has been synthesized and characterized by single-crystal X-ray diffraction analyses and magnetic, electrochemical, spectroscopic, and theoretical studies. Single-crystal X-ray diffraction studies display a planar porphyrin moiety with an axial NCS coordinated to the Fe(III) center. Electrochemical and spectroelectrochemical studies in solution depict clear changes in the system during the oxidation and reduction processes. Attempts to understand the origin of high magnetic anisotropy in the ground state, as determined by DC magnetic measurements, were undertaken by detailed CASSCF/QD-NEVPT2 calculations. Mössbauer spectroscopic analysis at different temperatures also supported this observation, which was further backed by DFT calculations depicting the magnetostructural correlation.