A theoretical study of the electron paramagnetic resonance spectra and local environment in copper(II) complexes with different imidazole and chlorido ligands

Copper(II) chloride anionic coordination complexes with different imidazole-derived ligands due to the potential cytotoxic activity play the important role in protein. By investigating the experimental electron paramagnetic resonance (EPR) and ultraviolet–visible (UV–vis) spectra of [CuCl(C₆H₁₀N₂)₄]Cl, [CuCl(C₆H₁₀N₂)₄]Cl, [CuCl₂(C₄H₆N₂)₄], and [Cu₂Cl₂(C₅H₈N₂)₆]Cl₂·2H₂O, the local structure of the corresponding Cu²⁺ centers and the role of different ligands are obtained. Based on the well-agreed EPR parameters and the d-d transitions (10D_q), the four Cu²⁺ centers show tetragonal and orthorhombic distortion, corresponding to the different anisotropies of EPR signals. In addition, the general rules of governing the impact of methanol in imidazolylalkyl derivatives are also discussed, especially the influence on the local environment (symmetry, distortion, covalency, and crystal field) of above four copper(II) chloride anionic coordination complexes. Therefore, the obtained results in this study will be beneficial to provide a theoretical basis for the experimental design of desired copper-containing imidazolyl alkyl derivatives.