Synthesis, spectroscopic analysis and structure deduction of gold(III), palladium(II) and platinum(II) complexes with the tripeptide glycyl-l-phenylalanyl-glycine

The coordination behaviour of the tripeptide glycyl-l-phenylalanyl-glycine (H-Gly-Phe-Gly-OH) with Au(III), Pd(II), and Pt(II) in both solution and in the solid state has been investigated experimentally. In addition, quantum chemical calculations have been carried out with a view to obtain the structures and spectroscopic properties of the ligand and its complexes. Both in solution and in the solid state the tripeptide interacts in a tetradentate manner with the Au(III) and Pd(II) ions through the NH2, two deprotonated amide N atoms and the COO−group, forming [Au(H-Gly-Phe-Gly-OH)H−2)] × H2O and [Pd(H-Gly-l-Phe-Gly-OH)H−2)]Na × H2O complexes. The MN3O chromophores are calculated to be near planar. Interaction with cisplatin leads to the formation of a mononuclear complex with tridentate coordination of the ligand by NH2 and two N- atoms from the deprotonated amide groups ([Pt(H-Gly-l-Phe-Gly-OH)H−2)NH3] × 2H2O). The fourth coordination position of the Pt(II) is occupied by an NH3 ligand. The PtN4 chromophore is flat with a deviation from planarity of 0.3°.