Platinum Metals Review - Volume 50, Issue 1, 2006

Ruthenium (Ru) complexes containing polyaminocarboxylate (pac) ligands (Ru-pac) have features which indicate they may be suitable for biological applications. For instance, Ru-pac complexes can bind to biomolecules through a rapid and facile aquo-substitution reaction, and Ru-pac has a range of accessible oxidation states. Ru-pac also has some notable catalytic properties that mimic enzymatic hydrocarbon oxidation by cytochrome P-450 in homogeneous conditions. This is of immense significance towards developing Ru-pac based agents for oxidative cleavage of DNA and artificial nuclease in DNA foot-printing experiments. This review aims to highlight the scope of Ru-pac complexes as metallopharmaceuticals, and outlines their potential for certain biological applications.

Scant data exist for the mechanical properties of commercial platinum jewellery alloys Pt-5 wt.% Cu and Pt-5 wt.% Ru. Here data from new evaluations are presented on 90% cold worked and fully recrystallised heat treated alloys at 800°C. Recommendations are made for procedures in reporting future evaluations including disclosure of full processing details.

Iridium crucibles, examined after being used in the extraction of gold and silver from residues remaining after zinc manufacture, showed an anomalously high permeability to substitutional components and impurities, such as gold. To discover the cause of this high permeability, the volume diffusion of gold into nominally pure single crystals of iridium (single-Ir), annealed under ultrahigh and technical grade vacuums, UHV and TGV, respectively, was studied at temperatures from 1300 to 2000 K. The coefficients of volume diffusion of gold into single-Ir were measured by secondary ion mass spectrometry. The activation enthalpies measured for volume diffusion of the gold were:andin UHV and TGV, respectively, for annealing single-Ir. On annealing in TGV, interstitial impurities formed vacancy-impurity complexes (VICs). The binding energy of the VIC components (EVIC)Ir = (116 ± 16) kJ mol ^–1. In TGV, the gold diffusion was determined by ‘extrinsic’ vacancies dissociating from the VICs. At typical working temperatures for iridium the concentration of the ‘extrinsic’ vacancies was several thousand times larger than the concentration of the equilibrium ‘intrinsic’ vacancies. The ‘extrinsic’ vacancies are responsible for the high coefficient of volume diffusion and the corresponding anomalously high mass transfer of gold into iridium during TGV annealing.