Search Results (2)

Luminescent diimine-Pt(IV) complexes [Pt(N^N)(Me)₂(PhSe)₂], (N^N = 2,2′-bipyridine (bpy, 1b), 1,10-phenanthroline (phen, 2b), and 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy, 3b), PhSe⁻ = phenyl selenide were prepared and identified using multinuclear (¹H, ¹³C{¹H} and ⁷⁷Se{¹H}) NMR spectroscopy. The PhSe⁻ ligands were introduced through oxidative addition of diphenyl diselenide to the non-luminescent Pt(II) precursors [Pt(N^N)(Me)₂], N^N = (bpy, 1a), (phen, 2a), (Me₂bpy, 3a), to give the luminescent Pt(IV) complexes 1b–3b. The UV-vis absorption spectra of 1b–3b are characterised by intense bands in the range 240–330 nm. We assigned them to transitions of essentially π−π* character with small metal and PhSe⁻ ligand contributions with the help of TD-DFT (time-dependent density functional theory) calculations. The weak long-wavelength bands in the range 350–475 nm are of mixed ligand-to-metal charge transfer (L’MCT) (n_(Se)→d_(Pt)/intra-ligand charge transfer (IL’CT) (n_(Se)→π*_(Ph) or π_(Ph)→π*_(Ph))/ligand-to-ligand’ charge transfer (LL’CT) (L = N^N, L’ = PhSe⁻, M = Pt and n = lone pair) character. The Pt(IV) complexes showed broad emission bands in the solid state at 298 and 77 K, peaking at 560–595 nm with a blue shift upon cooling. Structured emission bands were obtained in the range 450–600 nm, with the maxima depending on the N^N ligands and the solvent polarity (CH₂Cl₂ vs. dimethyl sulfoxide (DMSO) and aqueous tris(hydroxymethyl)aminomethane hydrochloride (tris-HCl) buffer). The emissions originate from essentially ligand-centred triplet states (³LC) with mixed IL’CT/L’MCT contributions as concluded from the DFT calculation. Such dominating PhSe contributions to the emissive states are unprecedented in the world of luminescent diimine-Pt(IV) complexes. Full article

The metal resistant bacterium Cupriavidus metallidurans CH34, challenged with aqueous platinous and platinic chloride, rapidly immobilized platinum. XANES/EXAFS analysis of these reaction systems demonstrated that platinum binding shifted from chloride to carboxyl functional groups within the bacteria. Pt(IV) was more toxic than Pt(II), presumably due to the oxidative stress imparted by the platinic form. Platinum immobilisation increased with time and with increasing concentrations of platinum. From a bacterial perspective, intracellular platinum concentrations were two to three orders of magnitude greater than the fluid phase, and became saturated at almost molar concentrations in both reaction systems. TEM revealed that C. metallidurans was also able to precipitate nm-scale colloidal platinum, primarily along the cell envelope where energy generation/electron transport occurs. Cells enriched in platinum shed outer membrane vesicles that were enriched in metallic, colloidal platinum, likely representing an important detoxification strategy. The formation of organo-platinum compounds and membrane encapsulated nanophase platinum, supports a role for bacteria in the formation and transport of platinum in natural systems, forming dispersion halos important to metal exploration. Full article