Five-coordinate Cu(II) complexes, [Cu(Ln)X]ClO4/PF6, where Ln = piperazine ligands bearing two pyridyl arms and X ClO4? for L1 (1-ClO4), L2 (2-ClO4), L3 (3-ClO4), L6 (6-ClO4) as well [Cu(Ln)Cl]PF6 (1-Cl), L4 (4-Cl), L5 (5-Cl) have been synthesized characterized by spectroscopic techniques. The molecular structures of the last complexes were determined X-ray crystallography. In aqueous acetonitr...