Ammonia decomposition on Ir and Pt wires

The rates of ammonia decomposition on polycrystalline Ir and Pd wires were measured at temperatures between 900 and 2000 K and at pressures between 50 and 770 Torr. Rates on Ir were fitted with a Langmuir-Hinshelwood unimolecular reaction rate expression. Rates on Pd could not be fitted with a rate expression, although activation energies were obtained.

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Ir Pd 900–2000 50–770 . Ir --. Pd . .

     

Absorption and emission spectroscopic characterization of Ir(ppy)3

The absorption and emission spectroscopic behaviour of cyclometalated fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)₃] is studied at room temperature. Liquid solutions, doped films, and neat films are investigated. The absorption cross-section spectra including singlet–triplet absorption, the triplet–singlet stimulated emission cross-section spectra, the phosphorescence quantum distributions, the phosphorescence quantum yields and the phosphorescence signal decays are determined. In neat films fluorescence self-quenching occurs, in diluted solid solution (polystyrene and dicarbazole-biphenyl films) as well as deaerated liquid solution (toluene) high phosphorescence quantum yields are obtained, and in air-saturated liquid solutions (chloroform, toluene, tetrahydrofuran) the phosphorescence efficiency is reduced by triplet oxygen quenching. At intense short-pulse laser excitation the phosphorescence lifetime is shortened by triplet–triplet annihilation. No amplification of spontaneous emission in the phosphorescence spectral region was observed indicating higher excited-state absorption than stimulated emission.     

Radioactivity characterization of 125I brachytherapy seeds used in prostate cancer treatment

Journal of Radioanalytical and Nuclear Chemistry - A procedure for characterizing the activity amount of 125I seed was developed in order to establish a secondary standard activity measurement...     

Synthesis and characterization of new type molecular wires with tetrathiafulvalene as redox center

A new type of molecular wire 1a – c with tetrathiafulvalene (TTF) units was synthesized and characterized. The UV–vis spectra and electrochemistry results showed that comparing with PPE, these polymers had smaller HOMO–LUMO band gap, and the HOMO level of polymer 1a (?5.05 eV) was closer to the work function energy of Au electrode. Thermal stability analyses indicated that these polymers had good thermal stability. All of the results showed that the introduction of TTF units made polymers 1a – c better candidates for molecular wires than PPE. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2707–2713, 2006     

Synthesis and characterization of half-sandwich Rh, Ir complexes containing mono-thiolate-ortho-carborane ligand

Two binuclear complexes [Cp^∗M(Cl)Carb^S]₂ (Cp^∗ = η⁵-C₅Me₅, M = Rh (1a), Carb^S = SC₂(H)B₁₀H₁₀, Ir (1b)) were synthesized by the reaction of LiCarb^S with the dimeric metal complexes [Cp^∗MCl(μ-Cl)]₂ (M = Rh, Ir). Four mononuclear complexes Cp^∗M(Cl)(L)Carb^S (L = BuⁿPPh₂, M = Rh (2a), Ir (2b); L = PPh₃, M = Rh (4a), Ir (4b)) were synthesized by reactions of 1a or 1b with L (L = BuⁿPPh₂ (2); PPh₃ (4)) in moderate yields, respectively. Complexes 3a, 3b, 5a, 5b were obtained by treatment of 2a, 2b, 4a, 4b with AgPF₆ in high yields, respectively. All of these compounds were fully characterized by IR, NMR, and elemental analysis, and the crystal structures of 1a, 1b, 2a, 2b, 4a, 4b were also confirmed by X-ray crystallography. Their structures showed 3a, 3b and 5a, 5b could be expected as good candidates for heterolytic dihydrogen activation. Preliminary experiments on the dihydrogen activation driven by these half-sandwich Rh, Ir complexes were done under mild conditions.     

Synthesis of Ir Catalysts Featuring Amide-functionalized NHC Ligands and Survey of their Activity on Formic Acid Dehydrogenation

2 a and 2 b , [Ir(CI)(COD)(NHC)] (COD=1,5-cyclooctadiene), have been prepared via transmetallation from NHC−Ag complexes. [Rh(CI)(COD)(NHC)] ( 4 ) was prepared analogously. [Ir({κ-C,N-(NHC-acetamide−1H)}(COD)] ( 3 c ) has been synthesized via transmetallation from the deprotonated NHC−Ag complex. [IrCp*({κ-C,N-(NHC-acetamide−1H)}] ( 5 ) (Cp*=pentamethylcyclopentadienyl), has been obtained analogously. [Ir(CI)(CO)₂(NHC)] ( 6 ) and [Ir({κ-C,N-(NHC-acetamide−1H)}(CO)₂] ( 7 ) have been prepared by carbonylation of 2 b and 3 c , respectively. The catalytic activity of these complexes has been evaluated in the dehydrogenation of formic acid, under solventless conditions, in the presence of water as a cosolvent, and in a 5 : 2 HCOOH/Et₃N mixture, with the best TOF values being obtained in the case of the latter. Stoichiometric experiments suggest COD hydrogenation as the preactivation step.     

Synthesis and characterization of [PW11O39Ir(H2O)]4-: successful incorporation of Ir into polyoxometalate framework and study of the substitutional lability at the Ir(III) site

The first Keggin-type heteropolyanion, [PW(11)O(39)Ir(H(2)O)](4-) (1), was synthesized by hydrothermal reaction from two different polytungstate precursors and [IrF(6)](2-). It was isolated as (Bu(4)N)(4)[PW(11)O(39)Ir(H(2)O)] (1a), which was completely characterized by multinuclear (31)P and (183)W NMR, ESI-mass spectrometry and cyclic voltammetry. A rapid screening methodology to ascertain the intrinsic substitutional lability at the Ir site is also presented, based on ESI-MS.     

Synthesis and characterization of green-emitting phosphorescent Ir(III) complexes based on phenyl benzimidazole ligand

Several new Ir(III) complexes with 2-(4-bromophenyl)-1H-benzo[d]imidazole or 2-(4-bromophenyl)- 1-methyl-benzo[d]imidazole ligands as cylcometalated ligand and acetylacetonate or picolinate as the ancillary ligand were synthesized and their structures and photophysical properties were characterized. HOMO and LUMO energy levels and the molecular structures of Ir(III) complexes were scrutinized by DFT calculations. The complexes exhibited green luminescence at the maximum emission peaks at ca 495–522 nm. The methyl group substituent and replacing of acetylacetonate with picolinate complex can enhance the complex thermal stability. HOMO energy levels of the complexes vary from –4.99 to –5.44 eV, the LUMO energy levels are between –1.52 and –1.97 eV.     

XPS characterization of SiO2-supported iridium producedin situ from Ir4(CO)12

The initial stage of Ir₄(CO)₁₂ physisorption on SiO₂ from solutions and the subsequent modifications induced by heating under different atmospheres are discussed with the help of XPS results obtained on samples treatedin situ. Ir₄(CO)₁₂ is shown to physisorb as crystallites. A good dispersion of crystallites on SiO₂ is obtainedvia heating at 373 K under Ar. Ir₄(CO)₁₂-supported clusters can be reduced to metal under mild conditions, with complete loss of ligands on controlled heating under Ar or H₂. The final products of the process are metal clusters, which are obtained at different nuclearities, depending on the duration of the process. We present the first report on the obtainment of Ir on SiO₂ at the same Ir4f_7/2 binding energy (b.e.) of bulk Ir.     

Synthesis and characterization of positively capped CdTe quantum wires that exhibit strong luminescence in aqueous media

The novelty of the current work lies in the versatile synthesis of highly luminescent water-soluble CdTe quantum rods (QR) which to the best of our knowledge are the first known water-soluble QR carrying positively charged stabilizer.     

Fulleropyrrolidine end-capped molecular wires for molecular electronics--synthesis, spectroscopic, electrochemical, and theoretical characterization

In continuation of previous studies showing promising metal-molecule contact properties a variety of C(60) end-capped "molecular wires" for molecular electronics were prepared by variants of the Prato 1,3-dipolar cycloaddition reaction. Either benzene or fluorene was chosen as the central wire, and synthetic protocols for derivatives terminated with one or two fullero[c]pyrrolidine "electrode anchoring" groups were developed. An aryl-substituted aziridine could in some cases be employed directly as the azomethine ylide precursor for the Prato reaction without the need of having an electron-withdrawing ester group present. The effect of extending the π-system of the central wire from 1,4-phenylenediamine to 2,7-fluorenediamine was investigated by absorption, fluorescence, and electrochemical methods. The central wire and the C(60) end-groups were found not to electronically communicate in the ground state. However, the fluorescence of C(60) was quenched by charge transfer from the wire to C(60). Quantum chemical calculations predict and explain the collapse of coherent electronic transmission through one of the fulleropyrrolidine-terminated molecular wires.     

Nuclear characterization and investigation of radioactive bioglass seed surfaces for brachytherapy via scanning electron microscopy

This paper aims to analyze images created through scanning electron microscopy (SEM) of the surfaces of radioactive bioglass seeds for brachytherapy implants. The SEM surface images were taken of bioglass seeds made of [Si:Ca:Ho] with Zr and Ba contrast agents and of seeds made of [Si:Ca:Sm] with Ba contrast agent. The following groups were considered: bioglass seeds after synthesis, seeds after irradiation and surface-induced fractures. The SEM image pre-processing required an appropriate mounting support following metallization with gold to fix the bioglass seeds made of inorganic elements. The microscope images were analyzed and showed surface changes among the seed groups. Nuclear characterization of the radioactive bioglass seeds by gamma spectrometry provided the gamma signatures of Sm-153 and Ho-166 followed by the contrast agents. The particle ranges on ceramic; water and tissue were also analyzed using gamma and beta particle evaluations. The results complement the study of the characterization and biodegradability of radioactive bioglass seeds for brachytherapy implants.     

Synthesis and x-ray characterization of the [Ir6(CO)15COEt]-Anionic Cluster

The reaction of Ir₆(CO)₁₆ with a mixture of CO, H₂, and ethylene yields the [Ir₆(CO)₁₅COEt]^- anion, which has been shown by X-ray diffraction to contain an octahedral iridium cluster bearing a —bonded acyl group; the arrangement of the 11 terminal and 4 edge-bridging carbonyl groups is different from that found in both the analogous rhodium complex and the parent Ir₆(CO)₁₆ carbonyl.     

Discrete half-sandwich Ir, Rh-based organometallic molecular boxes: synthesis, characterization, and their properties

The treatment of binuclear complexes [Cp*(2)M(2)(μ-QA)Cl(2)] (M = Ir, 2a; M = Rh, 2b) (H(2)QA = 1,4-dihydroxyanthraquinone) with pyrazine or bifuncational pyridyl-based ligands (4,4'-dipyridine (bpy), E-1,2-bis(4-pyridyl)ethene (bpe), 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo), and 2,5-bis(4-pyridyl)-1,3,4-thiadiazol (bpt)) in the presence of AgOTf (OTf = CF(3)SO(3)) in CH(3)OH, gave the corresponding tetra-nuclear complexes, with a general formula of [Cp*(4)M(4)(μ-QA)(2)(μ-L)(2)](OTf)(4) (M = Ir, 3a-7a; M = Rh, 3b-7b), respectively. The molecular structure of [Cp*(4)Ir(4)(μ-QA)(2)(μ-pyrazine)(2)](OTf)(4) (3a) has been determined by single-crystal X-ray analysis, revealing that the metal centers were connected by pyrazine and bis-bidentate QA(2-) ligands to construct a rectangular cavity with the dimension of 7.30 × 8.41 × 6.92 ?. Complexes 3a and 3b were found to exhibit selective trapping of halocarbons properties.     

Electrochemical fabrication and characterization of thin films of redox-active molecular wires based on extended Rh-Rh bonded chains

An original electrochemical synthesis of {[Rh4(mu-OOCCH3)4(phen)4]2+}n (1) molecular wire films from a solution of binuclear bridged Rh complexes [Rh2(mu-OOCCH3)2(phen)2(X)2](Y)2 (X = H2O, Y = BF4(-) (2a) and X = CH3CN, Y = BF4(-) (2b)) in MeCN electrolyte is reported. UV-vis spectroscopy and quartz crystal microbalance electrochemical coupled techniques have been used to demonstrate the electrosynthesis process. The resulting polymetallic compound has been characterized on the basis of its physicochemical properties, which have been compared with those of a chemically synthesized sample. Furthermore, according to EPR, 1H NMR and electrochemical behaviour, the mechanism of the oxidation of this polymetallic wire, containing mixed valent rhodium centers and alternatively acetate bridged Rh-Rh bonds, has been investigated in detail.     

Decomposition of hydrazine on Ir

The decomposition of N₂H₄ has been studied on polycrystalline Ir. It was found that hydrazine decomposition is very fast compared with other previously reported unimolecular reactions [3, 4]. Three products were detected, namely N₂, H₂ and NH₃. NH₃ formation rates were equal to those of N₂ formation up to about 700–800 K, depending on the pressure, but rapidly decreased above that temperature, while those of N₂ formation became flux-limited at high temperatures.     

不同载量Ir/C催化剂对氨氧化的电催化性能

研究电流型电化学氨气传感器阳极碳载Ir(Ir/C)催化剂电催化NH3氧化性能.实验表明,在NaC lO4中性电解液中,Ir/C催化剂对NH3氧化的电催化性能与Ir载量有关.其中以Ir载量为10%(by m ass)的Ir/C催化剂的电催化性能最好,稳定性和灵敏度也最高.此外,NH3在不同载量的Ir/C催化剂上电催化氧化的电流密度与NH3浓度均呈现出良好的线性关系,此类Ir/C催化剂在电流型电化学氨气传感器中可望有良好的应用前景.     

金属配比对IrRe催化剂结构及其甘油氢解催化性能的影响

采用分步-等体积浸渍法制备了不同Ir/Re摩尔比的Ir-Re/G-6双金属催化剂,并应用于甘油氢解制备1,3-丙二醇反应,利用XRD、TEM、H₂-TPR、XPS、NH₃-TPD、Py-IR和CO-DRIFTs等手段对催化剂进行了系统表征,探讨了Ir/Re摩尔比对Ir-Re催化剂结构、性质及其催化性能的影响.研究结果表明：Ir/Re摩尔比对Ir-Re双金属催化剂的合金结构和酸性能影响显著,并决定了其甘油氢解催化性能;当Ir/Re摩尔配比为1.0时,能形成高度分散的Ir-Re合金结构催化剂,具有最多的表面Brønsted酸性位（Ir-Re-OH）,表现出最高的甘油转化率和较好的1,3-丙二醇选择性.     

Development and Validation of Stability-Indicating Assay Method for a Novel Oxazolidinone (PH-192) with Anticonvulsant Activity by Using UHPLC-QToF-MS

The treatment of seizure disorders with currently available pharmacotherapeutic agents is not optimal due to the failure of some patients to respond, coupled with occurrences of side effects. There is therefore a need for research into the development of new chemical entities as potential anticonvulsant agents, which are different structurally from the existing class of drugs. We recently identified a novel triazolyl-oxazolidinone derivative, PH-192, as a potential anticonvulsant agent. PH-192 demonstrated protection comparable to phenytoin against both chemically- and electrically-induced seizures in rodents with little or no central nervous system side effects. However, PH-192 did not exhibit protection beyond 30 min; therefore, we decide to investigate a stability-indicating assay of PH-192 in plasma and other solutions. A reliable and validated analytical method was developed to investigate the stability of PH-192 for 90 min in human plasma, acidic, basic, and oxidative conditions, using a Waters Acquity ultra high-performance liquid chromatography (UHPLC) system with a quaternary Solvent Manager (H-Class). A simple extraction method indicated that PH-192 was stable in human plasma after 90 min at 37 °C, with more than 90% successfully recovered. Moreover, stress stability studies were performed, and degradants were identified using LC-QToF-MS under acidic, basic, and oxidative simulated conditions.     

Ru2(ap)4(sigma-oligo(phenyleneethynyl)) molecular wires: synthesis and electronic characterization

Reported in this contribution are the synthesis, characterization, and charge transport properties of wire-like Ru2(ap)4(OPEn), where ap is 2-anilinopyridinate and OPE is -(CCC6H4)nSCH2CH2SiMe3 with n = 1 (1) and 2 (2). Scanning tunneling microscopy (STM) measurements of compound 2 inserted into a SAM of C11 thiol reveal that molecule 2 exhibits (i) the stochastic switching characteristic of wire molecules embedded in insulating SAMs and (ii) higher conductivity than the C11 thiol SAM. More importantly, analysis of the molecular electronic decay constant (beta) exhibits a decrease of at least 15% as compared to purely organic molecular analogues. Hence, the transport characteristics of molecules can be significantly improved for nanoscale electronics through the incorporation of a Ru2 fragment into conjugated backbone.