Response mechanism of platinum electrode to uncoupled ions(Ⅰ)——Response of platinum electrode to Pb~(2+),Cd~(2+),Ca~(2+) and Mg~(2+)

The transient response mechanism of the platinum electrode to the uncoupled ions may be interpreted with the mixed phase formation (MPF) model of the transient response of precipitate-based ion-selective electrodes to interfering tons for Kxy<<1 It is discovered that the peak height of the transient signal is related to the solubility of M(OH)2 and hydration heat of M2+ The relation between the positive peak height of transient signal of Pb2+ or Cd2+ and lgaM obey tne Nernst equation,while that of Ca2+ or Mg2+ does not.The equilibrium potential is not of Nernst response for all ions.     

Vibrational spectroscope of complexes of platinum(0)—I. Tetrakis(triphenylphosphine)platinum(0) and Dioxygenbis(triphenylphosphine)platinum(0)

Assignment of i.r. and Raman spectra for Pt(PPh₃)₄ and Pt(O₂)(PPh₃)₂ yielded values for νPtP of 137 and 157 cm⁻¹ (Pt(PPh₃)₄); 132 (antisymmetric) and 145 cm⁻¹ (symmetric) (Pt(O₂)(PPh₃)₂). For the dioxygen complex, solution phase Raman spectra gave values for both ν PtO₂ modes for the first time. Data from the ¹⁶O₂, ¹⁶O¹⁸O and ¹⁸O₂ isotopomers were used in a normal coordinate analysis of the PtO₂ fragment. The OO stretching force constant (3.0 mdyn Å⁻¹) is consistent with extensive net π-back-donation into the π* m.o.s of the O₂ ligand.     

Exo-H- andendo-H-η4-pentamethylcyclopentadiene complexes of platinum

A mixture ofendo-H andexo-H isomers (1a and1b) of the (⁴-C₅Me₅H)PtCl₂ complex was prepared by the reaction of K₂PtCl₄ with C₅Me₅H in MeOH. The mixture of isomers reacts with CpTl in the presence of TiBF₄ to give a novel complex, [(⁴-C₅Me₅H)Pt(⁵-C₅H₅)]⁺BF₄ ^–, as a mixture ofendo-H- andexo-H-isomers (2a and2b). The data of¹H and¹³C NMR spectroscopy of the resulting complexes are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 514–517, March, 1994.     

Complexes of palladium,platinum and rhodium with 2,2′-biquinoline and 2-(2′-pyridyl)quinoline

Summary The reactions of 2,2-biquinoline(biq) with M(PhCN)₂X₂ (M=Pd; X=Cl or Br; M=Pt, X=Cl, Br or I), K₂PtCl₄ and RhCl₃·3H₂O and of 2-(2-pyridyl)quinoline (pq) with K₂PtCl₄ and RhCl₃·3H₂O have been investigated. The isolated complexescis-[Pd(biq)X₂] (X=Cl or Br),cis-[Pt(biq)Cl₂],cis-[Pt(biq)Cl₂]·H₂O,trans-[Pt(biq)₂Br₂]·5H₂O, [Pt₃(biq)₂I₆],mer-[Rh(biq)Cl₃-(H₂O)] andmer-[Rh(pq)Cl₃(H₂O)] have been characterized by elemental analyses, conductivity measurements, i.r., electronic, and¹H n.m.r. spectra. The reaction of pq with K₂PtCl₄ in 1M H₂SO₄ gave the salt 2-(2-pyridyl) quinolinium tetrachloroplatinate(II) pentahydrate, (pqH)₂[PtCl₄]·5H₂O; when the reaction was carried out in aqueous acetone,cis-[Pt(pq)Cl₂] was obtained. A new method for the synthesis ofcis-[Rh(biq)₂X₂]X (X=Cl or Br) is described; both compounds have been further characterized by¹H n.m.r.     

The reaction of diaryl derivatives of bis(triphenylphosphine)platinum(II) with [60]fullerene as a route to the platinum complex η2-C60Pt(PPh3)2

The reaction ofcis-Ar₂Pt(PPh₃)₂ (Ar=p-MeC₆H₄ (1a) and Ar=Ph (1b)) with [60]fullerene in toluene afforded the metal-fullerene complex η²-C₆₀Pt(PPh₃)₂ (2), which was isolated in the crystalline state. The reductive elimination between C₆₀ and1a or1b also resulted in the formation of biaryls (p-MeC₆H₄)₂ and Ph−Ph. The composition and structure of the compounds were established by¹H and³¹P NMR spectroscopy, electronic absorption spectroscopy, and elemental analysis. The homolytic phosphorylation of2 was additionally studied by the ESR method.     

Determination of trace platinum by supramolecular catalytic kinetic spectrofluorimetry of β–cyclodextrin–platinum–KBrO3–salicylaldehyde furfuralhydrazone

A supramolecular catalytic kinetic spectrofluorimetric method was developed for the determination of platinum(IV) and the possible mechanism of catalytic reaction was discussed. The method was based on the fluorescence-enhancing reaction of salicylaldehyde furfuralhydrazone (SAFH) with potassium bromate, which was catalysed by platinum(IV) in a water–ethanol medium. β–Cyclodextrin (β-CD) obviously sensitized the determination at pH 5.20 and 25°C. Under optimum conditions, the β-CD–platinum–KBrO₃–SAFH supramolecular kinetic catalytic reaction system had excitation and emission maxima at 372 and 461 nm, respectively. The linear range of this method was 0.60–180 ng ml⁻¹ with a relative standard deviation of 1.2%, and the detection limit was 0.18 ng ml⁻¹. Investigation of the mechanism and the effects of interferences is presented. The proposed method was applied successfully to determine trace platinum(IV) in the chemotherapeutic drug cisplatin and serum from patients with satisfactory results.      

Silica-supported chitosan–platinum complex catalyst for hydrosilylation reactions

Silica-supported chitosan–platinum complex was prepared and characterized by ICP-AES, FT-IR, and XPS, respectively. The complex as catalyst was found to display high catalytic activity in the hydrosilylation reaction of allyl glycidyl ether with triethoxysilane for the first time. It can be recovered by simple filtration and reused for six times without significant loss of activity.     

Molecular orbital calculations on platinum—gold heterometallic clusters

The bonding in some platinum—gold cluster compounds has been analysed using semi-empirical molecular orbital calculations. In (PtAu₂(PR₃)₄Cl]⁺ (I) and [Pt₂Au₂(PR₃)₄(CNR′)₄]²⁺ (II) the platinum—gold bonding involves three-centre two-electron bonds between the bonding orbital of the Au₂(PR₃)₂ dimer and the frontier orbitals of the T-shaped platinum fragments. The observed distortions in II have been satisfactorily rationalised. In [Pt₃Au(μ-CO)₃(PR₃)₄]⁺ (III) and [Pt₃Au(μ-SO₂)₂Cl(PR₃)₄] (IV) the AuPR₃⁺ fragments cap the Pt₃ triangles by utilising the acceptor orbital of a₁ symmetry localised on gold. The observed differences in bond lengths for these 54 and 56 electron clusters have been accounted for on the basis of the reduced overlap populations.     

Heterometallic binuclear complexes involving the mercury—platinum bond as a source of a platinum carbenoid in reactions with fullerene-60

The cleavage of two σ-bonds and the formation of a metallocomplex, (η²-C₆₀)Pt(PPh₃)₂, occur in a new reaction between fullerene-60 and binuclear heterometallic compounds having a mercury-platinum bond (retro-insertion promoted by C₆₀). One of these,trans- Ph₂CHCH₂HgPt(PPh₃)₂Br,1, which contains an electron-donating group at the mercury atom, reacts two orders of magnitude faster thancis-(CF₃)₂CFHgPt(PPh₃)₂CH=CPh₂,2, which has an electron-withdrawing substituent at mercury. An asymmetrical organomercury compound is the second product of the reaction. The reactants and products have been characterized by spectroscopic data (¹H,³¹P NMR, UV-VIS) and elemental analyses. Compound 2, which is more stable to retro-insertion, gives a Pt-centered free radical upon photolysis. This was used for the free-radical functionalization of C₆₀. The platinumfullerenyl radicalcis-C₆₀Pt(PPh₃)₂R² was identified by EPR spectroscopy.     

Amperometric glucose sensor based on platinum–iridium nanomaterials

This communication reports on a novel amperometric glucose sensor based on nanoporous Pt–Ir catalysts. Pt–Ir nanostructures with different contents of iridium were directly grown on Ti substrates using a one-step facile hydrothermal method and were characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy. Our electrochemical study has shown that the nanoporous Pt–Ir(38%) electrode exhibits very strong and sensitive amperometric responses to glucose even in the presence of a high concentration of Cl⁻ and other common interfering species such as ascorbic acid, acetamidophenol and uric acid, promising for nonenzymatic glucose detection.     

Oxidation of cyclohexene and α-pinene with O2—H2 mixture in the presence of supported platinum or palladium catalysts

Oxidation of cyclohexene and -pinene with an O₂—H₂ mixture in the catalytic systems containing Pt or Pd and heteropoly compounds (HPC) was studied. The main oxidation products are epoxides, allyl alcohols, and ketones. The highest yield of the oxidation products was obtained in the presence of the platinum catalyst in combination with HPC PW₁₁ or PW₁₁Fe. The reaction mechanism was proposed. A relationship between the HPC composition and the nature of intermediates involved in oxidation was examined.     

Catalysts with platinum–palladium nanoparticles on polymer matrix supports

The platinum–palladium/Nafion metal–polymer nanocomposites were synthesized by the chemical reduction of ions in the aqueous organic solutions of inverted microemulsions. The functional characteristics of the nanocomposites were studied by cyclic voltammetry, atomic force microscopy, and scanning electron microscopy. The nanocatalysts obtained exhibited high activity in the reactions of oxygen reduction and hydrogen oxidation. The influence of synthesis conditions on the catalytic activity of the metal–polymer nanocomposites was studied.     

Density functional theory study on quasi-three-dimensional oxidized platinum surface: phase transition between ��-PtO2-like and ��-PtO2-like structures

We investigate the oxidation process of a platinum surface by using the density functional theory approach under the periodic boundary condition. This oxidation process has received much attention because it is an initial step in the dissolution of platinum catalysts in polymer electrolyte fuel cells. In this research, we determine the optimized structure of ?? -PtO₂-like and ??-PtO₂-like oxidized platinum surfaces, which have recently been proposed on the basis of in situ X-ray diffraction analysis, at the Kohn Sham density functional theory (KS-DFT) generalized gradient approximation (GGA) level of theory. We discuss the phase transition from the ??-PtO₂-like surface to the ??-PtO₂-like surface, including the place-exchange reaction between oxygen and platinum atoms. We propose an intermediate structure in the phase transition, and show that the ??-PtO₂-like structure can be formed directly from this intermediate structure.     

O2-adsorption and (O2?H2)-titration on electron deficient platinum in reforming catalysts

Behavior of supported Pt in O₂ chemisorption and (O₂–H₂) titration has been studied. In Pt/SiO₂, Pt/-Al₂O₃ and Pt/-Al₂O₃ Pt^o catalysts are characterized by the following stoichiometric coefficients of oxygen adsorption (X), hydrogen adsorption (Y) and oxygen-hydrogen titration (Z) X:Y:Z=1:1:1.5. The co-efficients differ for Pt–Cl/-Al₂O₃ reforming catalysts. This is explained by the presence of electron deficient platium (Pt) with a coefficient ratio of X:Y:Z=0.5:2:1.5.     

Electrochemical and electrocatalytic behaviour of platinum–palladium nanoparticle alloys

The electrochemical and electrocatalytic behaviour of Pt/Pd nanoparticles prepared in water-in-oil microemulsion was reported. The catalytic activity of the nanoparticles was studied by using the reactions of dissociative adsorption of methanol and formic acid. The use of these surface probe reactions allowed the detection of palladium at the surface of the nanoparticles. The electrochemical stability of the particles was also investigated by voltammetry and electrochemical quartz crystal microbalance (EQCM). We shown that EQCM technique may be quantitatively used to correlate mass and area modifications when the electrochemical conditions produce corrosion of the elements of the alloy.     

Cytotoxic properties of platinum(IV) and dinuclear platinum(II) complexes and their ligand substitution reactions with guanosine-5′-monophosphate

The substitution reaction of the Pt(IV) complex [PtCl₄(bipy)] with guanosine-5??-monophosphate (5??-GMP) was studied by UV?CVis spectrophotometry. This reaction was investigated under pseudo-first-order conditions at 37?°C in 25?mM Hepes buffer (pH?=?7.2) in the presence of 10?mM NaCl to prevent the hydrolysis of the complex. The substitution of chlorides in [{trans-Pt(NH₃)₂Cl}₂(??-1,2-bis(4-pyridyl)ethane)](ClO₄)₂ (Pt3) complex by 5??-GMP was followed by ¹H NMR spectroscopy under second-order conditions. Very similar values for the rate constants of both substitution steps were obtained. The Pt(IV) complexes, [PtCl₄(bipy)] and [PtCl₄(dach)], as well as dinuclaer Pt(II) [{trans-Pt(NH₃)₂Cl}₂(??-pyrazine)](ClO₄)₂ (Pt1), [{trans-Pt(NH₃)₂Cl}₂(??-4,4??-bipyridyl)](ClO₄)₂?·?DMF (Pt2) and [{trans-Pt(NH₃)₂Cl}₂(??-1,2-bis(4-pyridyl)ethane)](ClO₄)₂ (Pt3) complexes, displayed potent cytotoxic activity against human ovarium carcinoma cell line TOV21G and lower activity toward human colon carcinoma HCT116 cell line at the same concentrations. Our data indicate that these platinum complexes could be explored further, as potential therapeutic agents for ovarian cancer.     

Visible light catalyzed aromatization of 1,3,5-triaryl-2-pyrazolines by platinum(Ⅱ) polypyridyl complex under oxidant-free condition

With visible light(λ=450 nm) irradiation of a catalytic amount of platinum(Ⅱ) terpyridyl complex, 1,3,5-triaryl-2-pyrazolines can be smoothly converted to their corresponding pyrazoles and hydrogen in quantitative yields with no use of any oxidant at room temperature.     

Efficient singlet oxygen generation by luminescent 2-(2′-thienyl)pyridyl cyclometalated platinum(II) complexes and their calixarene derivatives

Luminescent cyclometalated platinum(II) complexes, namely [Pt(Thpy)(PPh₃)X]ⁿ⁺ (HThpy = 2-(2′-thienyl)pyridine; X = Cl⁻ ( 1 ), n = 0; X = CH₃CN ( 2 ), pyridine ( 3 ), n = 1) and [Pt(Thpy)(HThpy)Y] ^{n +} (Y = Cl⁻ ( 4 ), n = 0; Y = pyridine ( 5 ), n = 1), exhibit structured emission with peak maximum at ∼556 and 598 nm in degassed acetonitrile and with emission quantum yield and lifetime of up to 0.38 and 26 μs, respectively. These complexes are efficient photosensitizers of singlet oxygen with yields up to >90%. Complex 5 exhibited photocytotoxicity towards cancer cells and fluorescence microscopic images of cells incubated with 5 reveal substantial uptake at the nucleus and mitochondria.