Five new copper(II) complexes containing bidentate terminal ligands and dianions of chloranilic acids (CA) have been synthesized, namely [Ca(phen)CA].H~2O(1; phen=o-phenanthroline), [Cu~2(phen)~2CA](ClO~4)~2 (2), [Cu(NO~2-phen)CA].H~2O(3; NO~2-phen=5-Nitro-o-phenanthroline), [Cu~2(NO~2-phen)~2CA](ClO~4)~2(4) and [Cu~2(bpy)~2CA](ClO~4)~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].H~2O moieties connected via hydrogen bonding whereas the structures of 2, 4 and 5 are built up by dimeric [Cu~2L~2CA]^2^+ cations and weak coordinated ClO~4^- 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 that ΔM~s=2 half-field transitions (Singlet-to-triplet). The variable- temperature magnetic susceptibilities of 2 and 5 have been measured (4- 300K). Based on the Heisenbery model, the exchange parameter, J, was found to be -29.2 and -25.7cm^-^1 for 2 and 5, respectively. An antiferromagnetic exchange interaction was suggested between the metal ions in these complexes.

Key words: MAGNETISM, SYNTHESIS, CHLORINE ION, DINUCLEAR COMPLEX, MONONUCLEAR COMPLEX, ELEMENTAL ANALYSIS, INFRA- RED, UV-DETECTOR, PARAMAGNETIC RESONANCE, TRIPLET