Stabilities and spectral properties of live-coordinate mixed-ligand copper(II) complexes containing N,N,N',N'',N''-pentamethyldiethylenetriamine and alpha-amino acids

Stabilities of the mixed-ligand copper(II) complexes [Cu(pmdt)(Am)](+) containing N,N,N',N*,N*-pentamethyldiethylenetriamine (pmdt) and 10 different a-amino acid anions (Am-) and their absorption, CD and ESR spectra are reported. The effect of the C- and N-substituent groups of the amino acid ligand on stability is examined. It was found that the stability depression of the N-substituent is large, while that of the C-substituent is quite small without regard to its bulkiness. The d-d absorption and X- and Q-band ESR spectra suggest that the ternary complexes are of the five-coordinate type with a trigonal bipyramid-based geometry, which causes the distinguishable substituent effect.