Computational insight into manganese(ii) complexes comprising macrocyclic ligands for magnetic resonance imaging

Abstract

The increasing interest in advances in the field of magnetic resonance imaging (MRI) and the promise of extensive development of Mn(II)-based MRI contrast agents have motivated us to investigate thoroughly manganese(II) complexes comprising macrocyclic ligands. Herein, 23 mononuclear Mn(II) complexes were selected and classified into five families based on the structural motif of the parent macrocycle. DFT methods were applied together with two implicit solvation models, the conductor-like polarizable continuum model (CPCM) and the solvation model based on density (SMD). The stability constants of Mn(II) complexes (log K_MnL), A(¹⁷O) hyperfine coupling values of aqua ligand(s), the zero-field splitting (ZFS) of the sextet ground state, and the thermodynamics of water dissociation were addressed and compared to the parameters applied in the analysis of the experimental data. Moreover, ZFS parameters were calculated using the multireference CASSCF/NEVPT2 method.