High-frequency and -field EPR and FDMRS study of the [Fe(H2O)6]2+ ion in ferrous fluorosilicate

► Spin Hamiltonian parameters for [Fe(H2O)6]2+ were determined by high-field EPR. ► Ligand-field theory analysis confirmed that the ground state of Fe2+ is 5A1. ► Unrestricted Hartree-Fock calculations properly reproduced the results. ► The Density Functional Theory was much less successful.