Unraveling the\nStability and Magnetic Properties of\nBis-Hydrated Mn(II) Complexes via Tailored Ligand Design

Exploring the electronic structure and dynamic behavior\nof Mn(II)\ncomplexes reveals fascinating magnetic properties and prospective\nbiomedical applications. In this study, we investigate the solvent\nphase dynamics of heptacoordinated Mn(II) complexes through ab initio\nmolecular dynamics simulations and density functional theory (DFT)\ncalculations with effectively varying temperatures. We observed that\nthe complex with high stability ([Mn(pmpa)(H<sub>2</sub>O)<sub>2</sub>]) remains relatively rigid as the temperature increases to 90 °C,\nwith only a minor change in its radial distribution functions (RDFs),\ncompared to the RDF peaks at 25 °C. To elucidate the impact of\nhalogens on the magnetic anisotropy of seven-coordinated Mn(II) complexes,\nwe performed both DFT and multireference calculations. This shows\nthat the zero-field splitting (ZFS) parameter <i>D</i> follows\nthe order <i>D</i>(I)> <i>D</i>(Br)> <i>D</i>(Cl). We observed a significant increase in the <i>D</i>-value following the substitution of soft Se-donors in\nthe equatorial\nposition and heavier halogens in the axial position. The <i>D</i>-value of halogen derivatives of Se-analogues varies in the order\nof <i>D</i>(Cl) < <i>D</i>(I) < <i>D</i>(Br), deviating from the regular spectrochemical series\nwith the discrepancy between the covalency of the Mn(II)–Se\nbond and the ligand field strength. We anticipate that this study\nwill enhance our understanding of the solvent phase dynamics and structural\naspects of ZFS in various Mn(II) complexes with different electronic\nenvironments.