Investigation of the EPR parameters and local structures for Cu2+ in Bis(l-asparaginato) M(II) catalysts (M=Zn, Cd, Mg) Original Research Article

The electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants) for Cu2+ in Bis(l-asparaginato) M(II) catalysts (M=Zn, Cd, Mg) are theoretically investigated using the high order perturbation formulas of these parameters for 3d9 ions in orthorhombically elongated octahedra. Ligand orbital and spin–orbit coupling contributions are included from the cluster approach in view of strong covalency. The ligand octahedra (i.e., [CuO4N2]12− clusters) are found to experience axial and perpendicular local bond length variations Δ (≈0.19–0.25 Å) and δ (≈0.12–0.14 Å) due to the Jahn–Teller effect and size mismatch, which are dissimilar to those of host M2+ sites in pure compounds. The theoretical EPR parameters based on the above local structures show good agreement with the observed values, and some improvements are achieved as compared with those in the previous work. The local structures of these centers are discussed.