Platinum ion

The Pt4f signal obtained with samples with high platinum loading (1 and S%) shows us that despite the low heating rate [0. Scc/min] used during the calcination of the san le, the deconqrosition of the tetramin platinum ion provoked the reduction ofthe ion at sqrerfdal level TPR results (Fig. 6) ow that this did not occur in the bulk... 

The wavenumbers of the MMCT transition between Pt(II) and Pt(IV) are related to the Pt(II)-Pt(IV) distance in the chain, as follows from a study of these compounds using different types of ligands. This relation is hnear [97]. ff the linear curve is extrapolated to a MMCT transition energy of zero, we obtain a distance equal to twice the Pt(IV)-ligand distance. This is the situation in which the Ugand, for example Cl or Br , is placed in between the two platinum ions, i.e. in which the difference between the platinum ions vanishes. 

Kowalska, E., Remita, H., Colbeau-Justm, C., Hupka, J., and BelloniJ. (2008) Modification of titanium dioxide with platinum ions and dusters application in photocatalysis. Journal of Physical Chemistry C, 112 (4), 1124-1131. 

The predominant binding site in 9-substituted 6-oxopurines (guanine and hypoxanthine derivatives) is the N7 atom of the base (Figure 6). The prevailing keto tautomer requires proton at N1 even in mildly acidic conditions, which efficiently prevents platination of the N1 site [7]. Under neutral and basic conditions competition of Pt(II) between the N1 and N7 sites has been reported. Attachment of Pt(II) to the N7 atom acidifies the N1H proton and facilitates coordination of additional platinum ions to both N1 and N3 [7]. In N7,N9-blocked 6-oxopurines, the N1 site is the major coordination site [7,24],... 

The complex was non-luminescent at room temperature, but it displayed luminescence in the solid state at 77 K, showing an unstructured emission at 443 nm. This emission was attributed to the gold centers or to the interaction between the gold and platinum ions. In fact, the isostructural [(NH3)4Pt][Ag(CN)2]1.4(H20) was not luminescent and, similarly, the corresponding [Ni(NH3)2][Au(CN)2]2, whose structure only showed gold-gold interactions (3.0830(5) A), did not display luminescence at either room temperature or at 77 K. 

Kim, S., S.J. Hwang and W.Y. Choi (2005). Visible light active platinum-ion-doped Ti02 photocatalyst. Journal of Physical Chemistry B, 109(51), 24260-24267. 

Attack on platinum is much more likely to occur when the solution contains ions capable of complexing platinum ions. Although relatively few couples possess a sufficiently high standard potential to oxidise platinum in 1 mol dm 3 HC104 where °(Pt2+/Pt) = 1.19 V, many more are thermodynamically capable of doing so in halide media since E PtCl /Pt) and E (PtCll /Pt) are only about 0.75 V [107]. Thus Cohen and Taylor [112] found that dissolution of platinum was the real reason why the metal ap-... 

Platinum cluster complexes with Pt—Pt bond(s) having various oxidation states are well known, and many exist in low-valent oxidation state, such as a series of [PtsCCOeln and phosphine or isocyanide clusters 1-9). A platinum ion with an odd d electron tends to form a dimeric complex having a Pt—Pt single bond involving the unpaired electrons. Monovalent platinum forms dimeric cluster complexes with a d -d configuration (10-14) and tervalent platinum forms d -d ... 

Preparation of carbon-bonded CH2COO complexes gives the impression that the platinum ion favors carbon-bonded structures as is known in the case of various mononuclear platinum complexes (26-29), and the tetraacetate complexes do not exist as stable compounds. The tetra(acetato)diplatinum complex, [Pt2(CH3C00)4(H20)2] (Fig. 8), was eventually prepared, however, by refluxing a solution of K2[Pt (NOalJ in CH3COOH-I M HCIO4 (2 1) (30, 31). 

Structural analysis disclosed that the PtNi complex takes a 4S geometry with the Pt atom coordinated by four sulfur atoms (Fig. 17). Acetonitrile is coordinated to the Ni site at the axial position to make the nickel ion hexacoordinated, including the neighboring platinum ion. The mean Pt - Ni distance (2.539 A Table I) is considerably shorter than the Pt Pt distance of [Pt2(4-mpyt)4]. 

In the Pt-doped hexagonal mesophase formed from CPCI (cetyl pyridinium chloride), platinum ions are adsorbed at the surface of the surfactant cylinders. They are reduced radiolytically into a metal layer as a nanotube of around 10 nm diameter and a few hundred nm long (Fig. 3f). Extraction of all these nanostructures is achieved by dissolution of the soft template using alcohol. This possible easy extraction constitutes a marked advantage over the synthesis in hard templates, such as mesoporous silica or carbon nanotubes, the dissolution of which is more hazardous for the metal nanostructures. 

This technique may be extended with strongly adsorbing acids such as oxalic tartaric, and citric. These adsorb preferentially on the outside forcing platinum ions deeper into the panicles, as shown in Fig. 6.16. 

CAT 1 = platinum ion-exchanged zeolites without salen CAT 2 = sublimation of salen into platinum ion-exchanged zeolites CAT 3 = zeolite USY impregnated with platinum salen complexes CAT 4 = AljOi impregnated with platinum salen complexes CAT 5 = SiOa impregnated with platinum salen complexes CAT 6 = homogeneous experiment without zeolite... 

Poly(vinylbenzyl chloride) resins bearing diamine and guanidine ligands have an excellent sorption ability towards platinum ions from hydrochloric acid solutions that is proportional to anion-exchange capacity [19]. These resins are characterized by their surface area, which includes pore radius, porosity in swollen state, water uptake, content of chloride and nitrogen and amino group capacity. 

In an effort to uncover the structures of DNA adducts of cisplatin, many reactions with the drug and synthetic oligonucleotides have also been carried out. Recently it has been shown that (1) and (2) can react in a cross-linking manner with the guanine residues in the trinucleotide d(GpTpG) [26]. In both cases, NMR measurements showed that the donor atoms bound to the platinum ions are two ammonia ligands and N-7 of guanine in positions 1 and 3 of the trinucleotide. 

The dimer (3) has been reported to react with calf thymus DNA [159]. Extended X-ray absorption fine structure (EXAFS) analysis of the platinated DNA revealed that the two platinum ions remained close to one another in the initially formed adduct (1 day incubation), but that over an extended period of time (8 day incubation) they separate from each other. In addition, compound (3) as well as its EtNH2 and Pr NH2 analogues, but not the hydrogen peroxide oxidation products of the complexes, are known to bind to and unwind supercoiled PM2-DNA (Peritz and Dabrowiak, unpublished data). 

There are important new applications of the aza-crown macrocycles for medicinal purposes. The perturbation of metabolic processes based on biological metal ion-ligand coordination can produce a disease or even death. Conversely, undesirable biological processes can be prevented by using certain metal ion-ligand interactions. For example, the weak complexing ability of chlorine to the central platinum ion of ds-platin (61) allows cw-platin to have antitumor activity (Haiduc and Silvestru, 1989). When applied in a biological... 

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