A series of tetrahedrally distorted copper(II) complexes with trochemical, UV/Vis-and EPR-spectroscopic features obtained experimentally. The calculations confirm for the thiolate and imine coordination were synthesized. Schiff bases derived from 4-benzoyl-3-methyl-1-phenyl-2-whole complex series a strong delocalization of the frontier orbitals. The highest fully occupied molecular orbital shows pyrazoline-5-thione and various diamines were used as tetradentate ligands to obtain tetrahedrally distorted metal a weak contribution, resulting from thiolate donor atoms, whereas the antibonding singly occupied molecular orbitals chelates with [CuN 2 S 2 ] complex units. Crystal structures of the complexes 1, 2, 5 and 6 and of ligand H 2 5 have been (SOMOs) are distributed between the copper(II) centre (ca. 35-40%) and the N 2 S 2 donor set. The SOMO energy determined by means of single-crystal X-ray structure analysis. The structure data show a strong influence of the significantly lowers with increasing tetrahedral distortion of the coordination sphere. The influence of the tetrahedral diamine building blocks on the tetrahedral distortion of the copper(II) complexes. Results of Extended Hückel LCAO distortion of copper(II) complexes on redox potentials, UV/ Vis and EPR spectra is discussed. calculations correlate strongly with structural, eleccycloolefins like α-pinene. [14Ϫ16] However, the role of the