Synthesis and spectroscopic characterization of copper(II) ternary complexes of 4-aminobenzoic acid and phenanthrolines

Solid state and solution EPR, and electronic spectroscopy, conductivity and magnetic susceptibility studies were carried out on a series of copper(II) complexes with different substituted phenanthrolines and 4-aminobenzoic acid. The ternary complexes were obtained as monomers of the type [Cu(pAb)2(phen)] [pAbH = 4-aminobenzoic acid, phen = unsubstituted phenanthroline (1) or 4,7-dimethyl-(2), 2,9-dimethyl-(3), 5-nitro-(4), 3,4,7,8-tetramethylphenanthroline (5)] or dimers of the type [Cu(pAb)(phen) (H2O)]2(NO3)2 [phen = 4,7-dimethyl-(6), 5-nitro-(7), 4,7-diphenylphenanthroline (8)] as a function of the condition of the reaction, as well as a function of the position of the substituents on the phenanthroline ligand. The formation of aromatic ring stacking interaction is a function of the geometry of the coordination sphere, as well as of the substituents on the phenanthroline ligand.