Binuclear copper(II) complexes of the tetradentate ligand 1,4-di(2′-pyridyl)aminophthalazine: some novel five-coordinate derivatives

Abstract

Reaction of the title ligand (L) with copper salts leads to the formation of three principal series of compounds, LCu2X3(OH)•H2O (X = Cl, Br), LCu2(RCO2)3, and LCu2(RCO2)4, where RCO2 represents various aliphatic and aromatic carboxylate species. Magnetic data, electronic spectroscopic data both at room temperature and at −196 °C, infrared spectra, and microanalytical data are correlated to reveal that these complexes contain a binuclear copper-copper system in which the copper atoms are 5-coordinate and square pyramidal. Brief details are presented of an X-ray structural analysis of the chloride complex confirming the structure proposed.The ligand forms complexes both in its neutral form and in an anionic deprotonated form. The ultraviolet spectra of the complexes distinguish these modes of bonding. The electronic spectra are discussed in terms of the 5-coordinate square pyramidal copper chromophore deemed to be present. In the complex L2Cu, the copper atom has a trigonally distorted 6-coordinate environment with tridentate anionic ligand.