Silver(I) and gold(I) complexes with penicillamine: Synthesis, spectroscopic characterization and biological studies

Two new metal complexes of penicillamine (Pen), with molecular formulas [Ag(C5H10O2NS)]·H2O and [Au(C5H10O2NS)], were synthesized by the reaction of the ligand with, respectively, silver nitrate and potassium dicyanoaurate(I) salts in aqueous solutions. Analytical characterizations of the complexes were based on elemental (C, H, N and S), thermal (TG-DTA) and electrospray ionization mass spectrometry (ESI-MS) analyses. Solid-state 13C nuclear magnetic resonance (SSNMR) and infrared (IR) spectroscopic measurements indicate coordination of Pen to Ag(I) or Au(I) through the sulfur atom. Studies based on density functional theory (DFT) confirmed that Pen acts as an S-donor ligand to Au(I) or Ag(I). Thermal decompositions of the silver(I) and gold(I) complexes start at temperatures near 50 °C, leading to the formation of Ag0 and Au0 at 700 °C and 500 °C, respectively. Both complexes are just slightly soluble in common solvents such as water, methanol, ethanol, acetonitrile, hexane and dimethylsulfoxide. An antibiogram assay was performed by the disc diffusion method. The AgPen complex showed antibacterial activities against Escherichia coli and Pseudomonas aeruginosa bacterial strains.

Structural formula proposed for the AgPen and AuPen complexes.Figure optionsDownload as PowerPoint slideHighlights
► Two new silver(I) and gold(I) complexes with penicillamine (Pen).
► Thermal and elemental analyses confirm molecular formulas as [Ag(C5H10O2NS)]·H2O and [Au(C5H10O2NS)].
► IR and 13C SSNMR permitted assigning sulfur coordination of Pen to the metals.
► The Ag(I) complex shows antibacterial activities against Gram-negative bacterial strains.