Au(III)-complexes of the alanyl-containing peptides glycylalanine and glycylalanylalanine - Synthesis, spectroscopic and structural characterization

As part of an investigation on the coordination ability of peptides, the dipeptide glycylalanine (H-Gly-Ala-OH), tripeptide glycylalanylalanine (H-Gly-Ala-Ala-OH) and their Au(III)-complexes have been characterized structurally. The quantum chemical calculations and linear-dichroic infrared (IR-LD) spectroscopy predict structures of the compound studied, which are compared with a single crystal X-ray diffraction of H-Gly-Ala-OH. The coordination processes with Au(III) are supported by data for 1H NMR, ESI-MS, HPLC-MS-MS, TGV and DSC methods. The [Au(Gly-Ala)H−1Cl] and [Au(Gly-Ala-Ala)H−2] · 2H2O complexes are formed via -NH2, N−amide/s and CO2- groups of the peptides. One Cl− ion is attached to the metal center as terminal ligand in the first complex. In both cases a near to square-planar geometry of the chromophors AuN2OCl and AuN3O is yielded.