SYNTHESIS AND MAGNETIC-PROPERTIES OF BINUCLEAR COPPER (II) COMPLEXES USING THE DIANIONS OF CHLORANILIC ACIDS AS BRIDGING LIGANDS

Five new copper(II)complexes containing bidentate terminal ligands and dianions of chloranilic acids(CA) have been synthesized, namely [Cu(phen)CA]. H2O (1; phen = omicron-phenanthroline), [Cu2(phen)2CA] (ClO4)2(2), [Cu(NO2-phen)CA].H2O(3; NO2-phen = 5-Nitro-omicron-phenanthroline), [Cu2(NO2-phen)2CA] (ClO4)2(4), and [Cu2(byp)2CA] (ClO4)2(5; bpy = 2, 2'-biphridyl). CA acts as bridging ligand in these compounds. All complexes have been characterized by elemental analyses, IR, electronic spectra, ESR, susceptibility and variable-temperature magnetic susceptibility. Complex 1, 3 might be associated in pseudodimeric entities formed by two [CuLCA].H2O moieties connected via hydrogen bonding whereas the structures of 2, 4 and 5 are built up by dimeric [Cu2L2CA]2+ cations and weak coordinated ClO4- anions. The copper(II) ion coordination geometry is probably distorted square pyramidal in the binuclear complexes. These complexes are very poorly soluble in water or common organic solvenos. Room-temperature ESR spectra of all the complexes studied show the DELTA-M(s) = 2 half-field transitions (Singlet-to-triplet). The variable-temperature magnetic susceptibilities of 2 and 5 have been measured (4-300 K). Based on the Heisenbery model, the exchange parameter, J, was found to be -29.2 and -25.7 cm-1 for 2 and 5, respectively. An antiferromagnetic exchange interaction was suggested between the metal ions in these complexes.