Bis(N-acetyl-DL-leucinate)copper(II) complexes and their amine adducts.

A compound of the type Cu(AcLeu)2 and its amine adducts of the type Cu(AcLeu)2Bn (AcLeu=N-acetyl-DL-leucinato ion; n=2 and B=pyridine, 3- and 4-methylpyridine, N-methylpiperazine, morpholine, and piperidine; n=1 and B=1,10-phenanthroline, 2,2′-bipyridyl, piperazine, and pyridazine) were prepared and investigated by means of electronic, infrared and EPR spectroscopy and magnetic moment measurements. The results suggest a tetragonal configuration for the Cu(AcLeu)2 complex and the amine adducts with CuO4 and CuO2N2 chromophores, respectively. For the green Cu(AcLeu)2·pid complex a binuclear configuration similar to that observed for the bis(acetato)copper(II) monohydrate complex is suggested. The amino acid in all the complexes is found to coordinate toward the carboxylato group. In the assignment of the way in which the carboxylato group coordinates, in addition to the difference between their antisymmetric and symmetric stretching frequencies, we also pay special attention to the position of the symmetric stretch, which is directly connected with the oxygen atom linked to the metal ion.