Theoretical investigations of the spin Hamiltonian parameters for the tetragonal [Rh(CN)4Cl2]4− complex in KCl

The spin Hamiltonian parameters (g factors, hyperfine structure constants and superhyperfine parameters) for the tetragonal [Rh(CN)4Cl2]4− complex in KCl are theoretically investigated from the perturbation formulas of these parameters for a 4d7 ion in a tetragonally elongated octahedron. This center can be assigned to the substitutional Rh2+ on host K+ site reduced from Rh3+ by capturing one electron during the electron irradiation, associated with the two axial ligands CN− replaced by two Cl−. The crystal-fields of the two axial Cl− are weaker than those of the four planar CN−, yielding the tetragonal elongation distortion. This system belongs to the case of low spin (S = 1/2) under strong crystal-fields, different from that of high spin (S = 3/2) under weak and intermediate crystal-fields (e.g., 3d7 ions such as Fe+ and Co2+ in conventional chlorides). The calculated spin Hamiltonian parameters show good agreement with the experimental data. The above [Rh(CN)4Cl2]4− complex due to the different axial and perpendicular ligands is unlike the tetragonally elongated [RhCl6]4− complex due to the Jahn–Teller effect in the similar NaCl:Rh2+ crystals.