Coordination properties of N-protected amino acids: simple and mixed (N-benzoyl-DL-leucinate)copper(II) complexes.

One green compound of the type Cu(BzLeu)2·2H2O and mixed complexes with amines of the type Cu(BzLeu)2·Bn·mH2O (n = 2, m = 0 and B = pyridine, 3- and 4-picoline and morpholine; n = 1, m = 2 and B = 1,10-phenanthroline, 2,2′-bipyridyl and piperazine) were prepared and characterized in the solid state by means oflow- and room-temperature magnetic measurements, room-temperature electronic, infrared and e.p.r. spectra. For the green compound, which displays physical characteristics similar to those of copper(II) acetate monohydrate and similar dimeric complexes, the complicated magnetic properties, discussed in detail, demonstrate the presence of a great amount (∼36%) of mononuclear copper(II) impurities, although the complex is analytically pure. For all the mixed complexes with amines, the physical measurements are consistent with a tetragonally distorted configuration of the copper(II) ion with the presence of a CuO4N2 chromophore. In all the complexes the amino acid coordinates only through the carboxylate group, acting as a ‘simple’ carboxylic acid.