Magnetism, IR and Raman spectra of a tetracoordinate and hexacoordinate Co(II) complexes derived from aminopyrimidine

Two mononuclear Co(II) complexes of the [CoCl2L2] and [CoCl2L4] family, with L being a heterocyclic N-donor ligand – 2-aminopyrimidine were prepared and subjected to magnetochemical investigation. Temperature dependence of the magnetic susceptibility and the field dependence of magnetization have been analyzed simultaneously in terms of the spin Hamiltonian formalism. The magnetic parameters obtained by a fitting procedure show a considerable magnetic anisotropy measured by the g-factor difference and the zero-field splitting parameter 2D, which splits the ground 4B1(D2d) term and/or 4A1g(D4h) term. The temperature dependence of the Far-IR spectra for the centrosymmetric hexacoordinate complex shows variable-temperature absorption peaks which yield the value of the zero-field energy gap ΔIR = 455 cm−1. Raman spectra, ab initio and DFT calculations assist in an accurate assignment of the absorption peaks.