SYNTHESIS, ELECTRON-PARAMAGNETIC RESONANCE AND X-RAY STRUCTURE CHARACTERIZATION OF COPPER(II) TERNARY COMPLEXES OF P-AMINOBENZOIC AND 3,4-DIMETHOXYHYDROCINNAMIC ACID WITH PHENANTHROLINES

Dimers of the type [Cu(pAb)(phen)(H2O)]2(NO3)2.2pAbH.2H2O (1) and [Cu(DPP)(4,7-phen)(H2O)]2(NO3)2.2H2O (2) (pAbH = p-aminobenzoic acid, DPPH = 3,4-dimethoxhydrocinnamic acid, phen = 1, 10-phenanthroline and 4,7-phen = 4,7-dimethyl-1, 10-phenanthroline) have been synthesized and characterized by means of EPR spectra in the solid and liquid states at room and low temperature, by magnetic measurements and by X-ray structure (1). Antiferromagnetic coupling of the unpaired electrons on each copper atom is evidenced by EPR spectra for both the compounds. They are, in fact, characteristic of dimers in which bridging nitrogen ligands are present. The Cu-Cu distance is 3.060 (1) angstrom and the dimer results through the bridging of two symmetry-related pAb molecules by bidentate carboxylic groups. The two phenanthroline molecules in the dimer are stacked with a minimum distance of 3.39 (1) angstrom.