Simple Platinum Research Articles

Photochemically Induced Cyclometalations at Simple Platinum(II) Precursors.

Photochemical cycloplatinations of 2-arylpyridines and related C∧N ligands, as well as terdentate heteroaromatic N∧N∧C, N∧C∧N, and N∧C∧C compounds, are demonstrated using (Bu4N)2[Pt2Cl6] or [PtCl2(NCPh)2] as precursors at room temperature. Mono- or bis-cyclometalated Pt(II) complexes with C∧N ligands are obtained depending on excitation wavelength and precursor. Monitoring experiments show that photoexcitation enables both the N-coordination and the subsequent C-H metalation. Photochemical synthetic protocols have been developed, which are advantageous with respect to the established thermal procedures and have allowed the synthesis of the first Pt(II) complexes with N∧C∧C ligands.

Study of a WO3 thin film based hydrogen gas sensor decorated with platinum nanoparticles

A simple platinum nanoparticle (Pt NP)/WO3 semiconducting metal oxide (SMO)-based structure is fabricated and completely studied as a hydrogen gas sensor. In this work, simple rapid thermal evaporation (RTE) was employed to fabricate Pt NPs. This approach could easily produce Pt NPs with a small grain size and uniformity on the WO3 thin film. Experimentally, at 200 °C, the studied device exhibited an excellent hydrogen sensing response of 1.41 × 106 (under a 1% H2/air gas), a very low detecting level of 1 ppm H2/air, and a relatively shorter response (recovery) time of 201 s (26) s. Moreover, first order differential (FOD) and shape-preserving piecewise cubic interpolation (SPPCI) were also employed to overcome the wireless transmission problem for the Internet of Things (IoTs). Furthermore, based on the thermodynamic analysis, the surface coverage performance was studied for this device. As the result, the studied device exhibited practically adsorption with hydrogen gas at 200 °C. The studied device is therefore promising for high-performance hydrogen sensing applications.

H2PO4-- and Solvent-Induced Polymorphism of an Amide-Functionalized [Pt(N^C^N)Cl] Complex.

A simple [Pt(N^C^N)Cl] complex functionalized with an amide group was prepared, and its absorption and emission properties were examined in different solvents in response to various anions. On the one hand, in the presence of H2PO4-, the solution of the complex shows distinct color changes in CH3CN, together with a ratiometric emission change from a green emission band at 537 nm to a deep red emission band at 680 nm. On the other hand, two-step spectral changes were observed in response to H2PO4- in CH2Cl2, with the green emission being attenuated first followed by the appearance of enhanced and yellow-green emissions at a lower-energy region. These recognition processes are highly selective for H2PO4- against other common anions including F-, Cl-, Br-, I-, OAc-, NO3-, and HSO4-. In addition, the platinum complex displays multistage emission polymorphism in mixed CH3CN/H2O solvent of various ratios. The hydrogen-bonding interaction between H2PO4- and the amide unit was confirmed by NMR analysis. In the solid state, this platinum complex emits red light. However, the composite material of the platinum complex with H2PO4- shows purely monomeric yellow emissions. The solid-state materials were further analyzed by single-crystal X-ray and Fourier-transform IR analysis. These studies suggest that this simple platinum complex is useful for the selective recognition of H2PO4- and as solid-state emitting materials with tunable emission colors.

Photoinduced Hydrogen Evolution from Water by a Simple Platinum(II) Terpyridine Derivative: A Z‐Scheme Photosynthesis

Mimicking nature: The photochemical H2 evolution from water catalyzed by a platinum(II)-based metalloviologen (PV2+) proceeds via the photoexcited state of the one-electron-reduced species (PV+.; see picture, EDTA=ethylenediaminetetraacetic acid). This artificial photosynthesis is reminiscent of the “Z-scheme photosynthesis” in green plants.

Photoinduced Hydrogen Evolution from Water by a Simple Platinum(II) Terpyridine Derivative: A Z-Scheme Photosynthesis

Der Natur nachgemacht: Die photochemische H2-Entwicklung aus Wasser, die von einem auf PtII basierenden Metallviologen (PV2+) katalysiert wird, verläuft über den photoangeregten Zustand der einelektronenreduzierten Spezies (PV+.; siehe Bild, EDTA=Ethylendiamintetraessigsäure). Diese künstliche Photosynthese erinnert an das „Z-Schema“ der Photosynthese in grünen Pflanzen.

A highly selective vapochromic methanol sensor based on one step synthesis of a simple platinum terpyridine complex

Abstract A novel and simple luminescent methanol sensor, [Pt(Cl-4-terpy)Cl]Cl ( 2 ) (Cl-4-terpy = 4-Chloro-2,2′:6′,2″-terpyridine), has been synthesized in good yield over 85%. Complex 2 was studied spectroscopically in both fluid solution and solid state. At room temperature, it is observed that 2 is weak emissive maximized at 612 nm in fluid solution and brightly luminescent maximized at 655 nm in the solid state. At 77 K, the solid state of 2 shows different properties, with two obvious peaks maximized at 590 and 675 nm. The complex exhibits reversible vapochromic behavior upon exposure to methanol vapors, changing color from red to yellow, with a blue shift in the emission from 655 to 615 nm, resulting from the disruption of intermolecular Pt···Pt interactions by methanol vapor. The vapochromic sensor also shows high selectivity for only methanol vapors among all the general available volatile organic compounds (VOCs) in the lab, even in the presence of water, and fast response (color change in less than 1 s).

Charge-scaled cavities in polarizable continuum model: Determination of acid dissociation constants for platinum-amino acid complexes

The main aim of this study is the calculation of acid dissociation constants of the products of cisplatin reaction with the amino acids cysteine and methionine. In the first step, a suitable procedure for the calculation of solvation Gibbs free energies is found, based on the comparison of the calculated and experimental pK(a)s of both amino acids and simple platinum complexes. The resulting approach combines the DFT/B3LYP density functional, 6-311++G(2df,2pd) basis set, the D-PCM formulation of the continuum solvation model, and modified UAHF cavities. Since the main area of applicability of the UAHF model is solvation of organic molecules, a minor modification of the UAHF algorithm was necessary to improve the accuracy when applying it to the transition metal complexes. Instead of the integer (or semi-integer) formal charges used in the original formulation, more realistic partial charges obtained from the electronic density using the NPA procedure are used to generate molecular cavity. All other parameters of the model remain unchanged. This simple modification of the UAHF model works markedly better than the original formulation. The root mean square error of calculated pK(a)s over a set of molecules including zwitterions and divalent diaquaplatinum cation is equal to 0.74. In the second step, pK(a)s of platinum amino-acid complexes with the total charge ranging from 0e to 2e were computed. It was found that the pK(a)s of all ionizable groups of both amino acids are highly variable among the complexes studied. They range from -5 (in complexes containing protonated thiol or carboxyl groups directly bonded to platinum) to 14 (in monodentate complexes containing a positively charged amino group, which is stabilized by intramolecular hydrogen bonds).

The Dilemma of the Wedding Band

The postoperative infection rate in procedures where no ring is worn, and those where a plain metal wedding band is worn under the glove was studied retrospectively. From January 1998 through June 2002, 2127 surgeries were performed by the lead author (D.T.S.), the first 2 years without a wedding band and the next 2 years with a simple platinum wedding band worn under the glove. Attention was paid to sliding the ring proximal and distal on the finger, ensuring scrub solution was under the ring and that the area of skin below the ring was cleansed. Twenty-two postoperative infections were recorded in 2127 surgeries. This is a postoperative infection rate of 1.0%, and <1 (0.449) postoperative infection per month. The "no ring" group totaled 987 cases with an infection rate 1.6%; the "ring" group revealed an infection rate of 0.53% in 1140 cases. Previous studies of jewelry in the operating room do not discuss the type of wedding ring worn, nor do they demonstrate an increased infection rate with wearing jewelry. This study suggests that there is no correlation between wearing a plain wedding band under the surgical glove and an increase in postoperative infections. The crevices and cuticle of the fingers and nails may provide more significant infection risk than a plain metal wedding band. This is a level III retrospective cohort study.

The Dilemma of the Wedding Band

The postoperative infection rate in procedures where no ring is worn, and those where a plain metal wedding band is worn under the glove was studied retrospectively. From January 1998 through June 2002, 2127 surgeries were performed by the lead author (D.T.S.), the first 2 years without a wedding band and the next 2 years with a simple platinum wedding band worn under the glove. Attention was paid to sliding the ring proximal and distal on the finger, ensuring scrub solution was under the ring and that the area of skin below the ring was cleansed. Twenty-two postoperative infections were recorded in 2127 surgeries. This is a postoperative infection rate of 1.0%, and <1 (0.449) postoperative infection per month. The "no ring" group totaled 987 cases with an infection rate 1.6%; the "ring" group revealed an infection rate of 0.53% in 1140 cases. Previous studies of jewelry in the operating room do not discuss the type of wedding ring worn, nor do they demonstrate an increased infection rate with wearing jewelry. This study suggests that there is no correlation between wearing a plain wedding band under the surgical glove and an increase in postoperative infections. The crevices and cuticle of the fingers and nails may provide more significant infection risk than a plain metal wedding band. This is a level III retrospective cohort study.

Liquid‐Liquid Biphasic, Platinum‐Catalyzed Hydrosilylation of Allyl Chloride with Trichlorosilane using an Ionic Liquid Catalyst Phase in a Continuous Loop Reactor

AbstractThe platinum‐catalyzed hydrosilylation of allyl chloride with trichlorosilane was investigated in an ionic liquid‐organic biphasic reaction mode. After an ionic liquid screening and repetitive batch mode experiments, the process was realized in a continuous mode using a loop reactor concept with integrated continuous separation and recycling of the ionic liquid catalyst phase. The continuous reactor could be operated for 48 h at constant activity and selectivity without addition of platinum indicating that platinum leaching into the product phase was far below 1 ppm. Enhanced selectivity for the product trichloro(3‐chloropropyl)silane (compared to the state‐of‐the art) and the possibility to use simple platinum tetrachloride (PtCl4) as platinum source are further attractive features of this new ionic liquid‐based process concept.

Synthesis and crystal structures of platinum (II) complexes with phosphine sulfide: cis-Dichloro[dimethylsulfoxide](triphenylphosphine sulfide) platinum (II) and (−)- cis-dichloro[( S)-methyl- p-tolylsulfoxide](triphenylphosphine sulfide) platinum (II)

The addition of triphenylphosphine sulfide (Ph 3PS) to bis-sulfoxide platinum (II) complexes [Pt(Me 2SO) 2Cl 2] and (−)-[Pt(Me- p-TolSO) 2Cl 2] yields mixed ligand complexes [Pt(Ph 3PS)(Me 2SO)Cl 2] ( 1) and (−)-[Pt(Ph 3PS)(Me- p-TolSO)Cl 2] ( 2), which are effective catalysts for hydrosilylation reaction. These mixed-ligand complexes were obtained in crystal state and analyzed by X-ray diffraction, 1H, 31P and 195Pt NMR; 2 was also studied by circular dichroism spectroscopy. Both complexes exist in CDCl 3 solution as a dynamic equilibrium of two geometric isomers with an approximate 1:10 ratio, but only cis-isomer is obtained on crystallization. The X-ray structures of the complexes have classical geometry, and phosphine sulfide and sulfoxides are coordinated via sulfur. The new structural data for simple platinum–Ph 3PS coordination bond, unaffected by chelation or bridging, were evaluated. The lengths of this bond are 2.300(4) Å in 1 and 2.305(3) Å in 2, respectively. PtSP angle equals 105.7(2)° in 1 and 104.05(13)° in 2, the PtSP plane is almost perpendicular to the coordination plane. The static trans-influence of Ph 3PS is estimated to be strong and close to that of S-coordinated Me 2SO. The complex 2 exhibits strong circular dichroism at a wavelength below 330 nm, caused both by inherent Me- p-TolSO stereogenic center and induced asymmetry of Ph 3PS.

Platinum Complexes of Dibenzo[1,2]Dithiin, Dibenzo[1,2]Dithiin Oxides and Related Polyaromatic Hydrocarbon Ligands

The synthesis of platinum bisphosphine complexes of biphenyl- 2,2'-dichalcogenates and the oxides of dibenzo[1,2]dithiin and related ligand systems by oxidative addition to [Pt(PPh(3))(4)] is reported. We also describe the synthesis of a new compound, dibenzothiophen-4-yldiselenide and its simple platinum complex (obtained by oxidative addition). All complexes have been fully characterised, principally by using multinuclear NMR spectroscopy and in six cases by means of single-crystal X-ray diffraction studies. The majority are simple S/S or Se/Se complexes, however the addition of dibenzo[1,2]dithiin trioxide to [Pt(PPh(3))(4)] gives a bimetallic system, [Pt[2-[S(O)],2'-[S(O)(2)]-biphen}(PPh(3))](2), containing a central Pt(2)S(2)O(2) core in which the ligand behaves as a tridentate S,S,O donor.

Asymmetric Synthesis of Coordination Compounds: Back to the Roots. Diastereoselective Synthesis of Simple Platinum(IV) Complexes

Asymmetric Synthesis of Coordination Compounds: Back to the Roots. Diastereoselective Synthesis of Simple Platinum(IV) Complexes

Asymmetric Synthesis of Coordination Compounds: Back to the Roots. Diastereoselective Synthesis of Simple Platinum(IV) Complexes

AbstractA publication by Alexander P. Smirnoff in Helvetica Chimica Acta in 1920 [6] describes the first synthesis of a coordination species, i.e., of tris(propane‐1,2‐diamine‐κN1,κN2)platinum(4+) ([PtIV(pn)3]4+), where it was shown that the configuration of a chiral center in the ligand can influence the configuration at the metal. The present investigation of [PtIV(pn)3]4+ was carried out by NMR spectroscopy, where all nuclei in the metal complex were used as sources of information, i.e., 1H, 13C, 15N, and 195Pt. 13C‐NMR and 15N‐NMR spectroscopy (of isotopically enriched complex) were especially informative for the analysis of isomer distribution. Stereoselectivity in the formation reaction of the complexes is rather modest, whereas Δ‐, and Λ‐isomers can be separated efficiently by crystallization. A mixture of [Pt{(S)‐pn}3]4+ and [Pt{(R)‐pn}3]4+ shows no scrambling of the enantiomeric ligands, thus proving the inertness of the complexes.

Oxygen radical density measurement in O2–N2 gas mixture plasma by means of a thin platinum wire

AbstractThe oxygen radical density was measured in a weakly ionized plasma in an O2–N2 gas mixture by using a simple platinum thin‐wire sensor. The increased temperatures of the platinum wire caused by the energy released in the recombination of two oxygen radicals on the platinum surface were measured by varying the nitrogen gas mixture ratio and were compared with the oxygen radical densities theoretically calculated under the same plasma conditions. The relation between the wire temperature and the oxygen radical densities was cross‐checked by quantitative measurement of oxygen radical densities with a quadrupole mass spectrometer. All of these results made it possible to determine the oxygen radical density experimentally from the platinum wire temperature alone. The influence of the ambient gas temperature on the radical density measurement is also discussed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 14–20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20018

The Air/Platinum/Nafion Triple-Phase Boundary: Characteristics, Scaling, and Implications for Fuel Cells

This contribution examines the heterogeneous kinetics of the oxygen reduction reaction (ORR) at the Pt/Nafion/air triple-phase boundary (TPB). This system is of particular interest for low-temperature polymer electrolyte membrane fuel cell applications. A focused ion beam system is used to prototype geometrically simple platinum microstructures directly on Nafion electrolyte membranes. By varying the size and shape of the platinum structures, the role and properties of the TPB are elucidated. Current-voltage and electrochemical impedance spectroscopy measurements reveal that the ORR kinetics scale with TPB length. A faradaic resistance per unit TPB length of Ω μm is extracted under short-circuit conditions at room temperature. Although this value is determined from microscopic measurements of geometrically simple platinum structures, it is successfully applied to predict the bulk performance of large-area sputtered platinum catalyst fuel cells. © 2004 The Electrochemical Society. All rights reserved.

Geometric hydration shells for anionic platinum group metal chloro complexes.

Solvation shells surrounding complex inorganic anions have not been extensively studied and are often mentioned with an amorphous picture in mind. We use a computational model previously validated against experimental results and ab initio quantum calculations (Lienke, A.; Klatt, G.; Robinson, D.; Koch, K. R.; Naidoo, K. J. Inorg.Chem. 2001, 40, 2352-2357) to investigate the nature of the hydration shells about simple platinum group metal chloro complexes ([PtCl(6)](2-), [RhCl(6)](3-), [PtCl(4)](2-), and [PdCl(4)](2-)). Our simulations show that the hydration shells surrounding these complexes are symmetric and take on familiar geometric forms. We find that only the [RhCl(6)](3-) complex has a clearly defined second hydration shell while the [PtCl(6)](2-), [PtCl(4)](2-), and [PdCl(4)](2-) second hydration shells are more diffuse.

Exploration of the atmospheric lower layer thermal turbulences by means of microthermocouples

The experiments on the propagation of acoustic air waves in the low atmospheric layer show a large influence of aerological parameters. In particular, there were only few measurements carried out outdoors to approach thermal turbulent values [1]. There are many thermal sensors ranging from a simple platinum resistance to quartz crystal. Each technology has some advantages depending on the type of measurement one intends to perform. To explore the earth boundary layer, we chose a micro-thermocouple of type S. Its small size (1.27 µm) allows us to obtain a low calorific capacity and a high thermal conductance. On the other hand, its sensitivity is low and it was necessary to associate an amplifier with a gain of 100 000. The whole device was set outside on a bar 2 m above the ground. The different experiments carried out with one or several microthermocouples showed very small turbulences of different types depending on the role of the different layers in the low atmosphere. They also enabled to visualize convection due to the ground or due to the wind as a function of time.

Kinetics and mechanism for chloride anation of some platinum(IV) aqua complexes in the presence of platinum(II)

Chloride anations of PtCl 5H 2O −, trans-PtCl 4(H 2O) 2 and trans-Pt(CN) 4ClH 2O − in the presence of PtCl 4 2− have been studied at 50°C in 1.00M perchloric acid medium. It is shown that PtCl 5H 2O − is formed as the primary reaction product in the two last-mentioned anations. This is not compatible with the generally used mechanism for platinum(II)-catalyzed platinum (IV) substitutions, which gives PtCl 6 2− as the direct reaction product for these two reactions. Other examples of formation of aqua complex intermediates in previously studied platinum(II)-catalyzed platinum (IV) substitutions can be found by examination of data from the literature. The chloride anation of PtCl 5 H 2O − follows the rate law: rate = k′ + k″ [Cl −] 1 + k‴[Cl −] [PtCl 4 2−][PtCl 5H 2O −] The usual interpretation of k‴ as the stability constant for a five-coordinate complex PtCl 5 3− is ruled out by other experiments, which indicate a much smaller stability constant than that obtained from the kinetics. This is also supported by a stopped-flow study at 25°C in 0.5 M perchloric acid medium of the substitution of bromide by chloride in trans-Pt(NH 3) 4Br 2 for large concentrations of entering ligand and in the presence of Pt(NH 3) 4 2+. A modified reaction mechanism is suggested which can describe all experimental results. The primary step is the formation of a dimer complex from the platinum(IV) substrate complex and the simple platinum(II) complex, hydrated in the axial positions. This dimer might decompose directly to a platinum(II) complex and a platinum(IV) aqua complex. Alternatively, it might react with the incoming ligand to form a new dinuclear complex, which decomposes to the platinum(II) complex and the substituted platinum(IV) complex.

OXYGEN TENSION MEASUREMENT BY A METHOD OF TIME SELECTION USING THE STATIC PLATINUM ELECTRODE WITH ALTERNATING POTENTIAL

1. The possibility of obtaining sustained and reproducible results in the analysis of dissolved oxygen with simple platinum electrodes by means of the application of a periodic potential pattern was explored over a wide range of frequencies and with a variety of wave forms. 2. Satisfactory results were obtained by the application in the frequency range of 5 to 10 C.P.M. of a square wave consisting of a positive and a negative pulse with interposed shorting periods and observing the current flowing at the end of each successive negative pulse. This was found to be linearly proportional to O(2) concentration for a pulse duration of the order of 1 second when the RC constant of the circuit was sufficiently small. 3. An instrument was developed to provide the required wave form and record the terminal currents of the negative pulses. The instrument provides either for recording of current voltage curves (polarograms) or for continuous recording at a fixed voltage of diffusion limited current values. 4. Typical measurements of oxygen uptake with yeast suspensions illustrate the application of the technique to problems requiring frequent determinations during short intervals. 5. Applications of this technique to biological and other problems are indicated with its limitations.