Tetragonally compressed high-spin Mn(III) Schiff base complex: Synthesis, crystal structure, magnetic properties and theoretical calculations

The synthesis, X-ray crystal structures, magnetic properties and Density Functional Theory (DFT) calculations of a new six-coordinated high-spin (HS) Mn(III) Schiff base complex, [Mn^III(3-MeO-sal-N(1,5,9,13))]NO ₃ (1), are described. The crystal structure analysis show that the Mn site has a tetragonally compressed octahedral geometry. The magnetic susceptibilities measurements indicate the HS ground state in the temperature range 1.8-300 K, in contrast with a previously reported analogue, [Mn(5-Br-sal-N-1,5,8,12)]ClO₄, which showed spin-crossover (SCO) behavior. The magnetic data are well fitted by Zero-Field-Splitting (ZFS) Hamiltonian, showing a D > 0 parameter, in line with the compressed octahedron pattern. Various DFT computations certified, in semi-quantitative respects, the fitted Spin Hamiltonian parameters. Computational experiments using fractional population schemes or Time-Dependent DFT approach yielded the specific ligand field parameters, contributing to the theoretical insight in the rare case of compressed Mn(III) complexes.