Mononuclear Au(III)-complexes with tryptophan-containing dipeptides: Synthesis, spectroscopic and structural elucidation

The coordination ability of dipeptides L-tryptophyl-L-phenylalanine (H-Trp-Phe-OH) and L-tyrosysl-L-tryptophan (H-Tyr-Trp-OH) with Au(III) have been elucidated both in solid state and in solution by means of series of methods as UV, H-1 and C-13 NMR, conventional and linear-polarized IR-spectroscopic tool in solid-state, based on orientation technique as suspension in nematic liquid crystal, FAB-MS, TGV, DSC methods and elemental analysis. The structures of the Au(III)-complexes have been predicted theoretically by DFT calculations at B3LYP level of theory and Lanl2DZ (Au)/6-31+G(3df) (Cl, C, H) basis set. The last data are compared with IR-LD spectroscopic ones giving the experimental evidence of the structures of the complexes studied. The dipeptides interact as tridentate ligands in obtained mononuclear complexes via their -NH2, deprotonated N--amide and CO2--groups at molar ratio metal to ligand 1:1. One Cl- ion is joined to the Au(III) as terminal ligand, forming [Au-III(LH-1)Cl] species. A near to square-planar flat geometry of the chromophores AuN2OCl is yielded with maximal deviation of total planarity less than 0.9 degrees. (C) 2006 Published by Elsevier B.V.