Terpyridine platinum(ii) complexes containing triazine di- or tri-thiolate bridges: structures, luminescence, electrochemistry, and aggregation

Dinuclear complexes [{Pt(trpy)}(2)(L)](PF(6))(2) (trpy = 2,2':6',2'-terpyridine, L = 2-octylthio-1,3,5-triazine-4,6-dithiolate ion (1), L = 2-octadecylthio-1,3,5-triazine-4,6-dithiolate ion (2), L = 2-di-n-butylamino-1,3,5-triazine-4,6-dithiolate ion (3)) and a trinuclear complex [{Pt(trpy)}(3)(L)](PF(6))(3) (L = 1,3,5-triazine-2,4,6-trithiolate ion (4)) have been synthesized and characterized. The single crystal X-ray analysis revealed that the two {Pt(trpy)}(2+) fragments in 1 and 3 adopt a syn-configuration. The PtPt distances are around 4.3 ?, suggesting no intramolecular PtPt interactions. Complexes 1-4 in acetonitrile show broad absorption bands at around 470 nm, assigned to mainly the ligand-to-ligand charge transfer ((1)LLCT) from triazine thiolates to trpy based on the comparison to the related complexes and the density functional theory (DFT) calculations. The red luminescence of 1-4 in acetonitrile is attributable to emission predominantly from (3)LLCT. Cyclic voltammograms of 1-3 exhibit four redox couples from -2.0 V to 0 V vs. Ag/AgCl. The two consecutive processes at around -0.70 V are assigned to the sequential reduction of two trpy ligands. This assignment was further supported by the observation of the anion radical of trpy in spectroelectrochemical experiments. The splitting of the redox potentials of two trpy ligands evidences the moderate electronic coupling interactions mediated by the triazine dithiolate bridges. Complex 2 formed a transparent red gel in CH(3)CN, whereas 4 produced a gel-like solid in the mixtures of CH(3)CN and other solvents. The interactions dominating the aggregative behaviours have been discussed based on the results of electronic absorption and emission spectroscopy.     

A unified route to the welwitindolinone alkaloids: total syntheses of (-)-N-methylwelwitindolinone C isothiocyanate, (-)-N-methylwelwitindolinone C isonitrile, and (-)-3-hydroxy-N-methylwelwitindolinone C isothiocyanate

As part of a comprehensive strategy to the welwitindolinone alkaloids possessing a bicyclo[4.3.1]decane core, we report herein concise asymmetric total syntheses of (-)-N-methylwelwitindolinone C isothiocyanate (2a), (-)-N-methylwelwitindolinone C isonitrile (2b), and (-)-3-hydroxy-N-methylwelwitindolinone C isothiocyanate (3a) from a common tetracyclic intermediate. The crucial vinyl chloride moiety was installed through electrophilic chlorination of a hydrazone, but only after adjustment of reactivity to circumvent a facile skeletal rearrangement. Selective desulfurization and oxidation of 2a provided access to 2b and 3a, respectively. Notably, this work provides corrected (1)H and (13)C NMR spectral data for 3a.     

Nanosize-induced drastic drop in equilibrium hydrogen pressure for hydride formation and structural stabilization in pd-rh solid-solution alloys

We have synthesized and characterized homogeneous solid-solution alloy nanoparticles of Pd and Rh, which are immiscible with each other in the equilibrium bulk state at around room temperature. The Pd-Rh alloy nanoparticles can absorb hydrogen at ambient pressure and the hydrogen pressure of Pd-Rh alloys for hydrogen storage is dramatically decreased by more than 4 orders of magnitude from the corresponding pressure in the metastable bulk state. The solid-solution state is still maintained in the nanoparticles even after hydrogen absorption/desorption, in contrast to the metastable bulks which are separated into Pd and Rh during the process.     

Finding hydrogen-storage capability in iridium induced by the nanosize effect

We report nanosize-induced hydrogen storage in Ir, which does not absorb hydrogen in its bulk form. The mean diameter of the obtained Ir nanoparticles was estimated as 1.5 ± 0.5 nm by transmission electron microscopy. Hydrogen storage was confirmed by solid-state (2)H NMR and hydrogen pressure-composition isotherm measurements.     

Intramolecular oxycyanation of alkenes by cooperative Pd/BPh3 catalysis

The cooperative catalysis by palladium and triphenylborane effects the intramolecular oxycyanation of alkenes through the cleavage of O-CN bonds and the subsequent insertion of double bonds. The use of 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) as a ligand for palladium is essential for allowing the transformation to proceed with high chemo- and regioselectivity. Variously substituted dihydrobenzofurans with both a tetra-substituted carbon and cyano functionality are accessed by the newly developed methodology.     

Conformity and precision of CO2 densimetry in CO2 inclusions: microthermometry versus Raman microspectroscopic densimetry

To assess the ability of densimetry for CO₂ fluid in CO₂ inclusions, we compare two methods, microthermometry and Raman microspectroscopic densimetry for CO₂. The comparative experiment was performed for nine CO₂ inclusions in three mantle xenoliths. The results are as follows: (1) microthermometry precisely determines CO₂ density with the range of 0.65 to 1.18 g/cm³ compared with Raman microspectroscopic densimetry; (2) CO₂ density obtained by Raman microspectroscopic densimetry is fairly consistent with that by microthermometry; (3) it is hard to determine CO₂ density in CO₂ inclusion with diameter of less than around 3 µm using microthermometry; and (4) microthermometry can be applied only to the CO₂ inclusion whose CO₂ density ranges from around 0.65 to 1.18 g/cm³, whereas the Raman microspectroscopic densimetry is applicable to CO₂ density ranging from 0.1 to 1.24 g/cm³. The above features carry the potential for estimation of depth origin of mantle‐derived rocks. The depth where the rocks were trapped by host magma can be estimated using both geothermometric data and CO₂ fluid density in CO₂ inclusions in the rocks. Typical precisions of density of CO₂ in CO₂ inclusions obtained by the Raman microspectroscopic densimetry (~0.01 g/cm³) and by the microthermometry (< 0.001 g/cm³) correspond to uncertainties in the depth origin of 2.4 km and < 1.7 km, respectively, at 1000 ± 50 °C. In case of the mantle under 750–1250 °C and 1 GPa, the CO₂ fluid has a density ranging from 1.06 g/cm³ to 1.21 g/cm³, which are well measured by the Raman microspectroscopic densimetry. Combination of both densimetries for CO₂ in mantle minerals elucidates the deep structure of the Earth. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison of ultrasonic degradation rates constants of methylene blue at 22.8 kHz, 127 kHz, and 490 kHz

Techniques such as solvent extraction, incineration, chemical dehalogenation, and biodegradation have been investigated for the degradation of hazardous organic compounds. We found ultrasound to be an attractive technology for the degradation of hazardous organic compounds in water. However, the effects of ultrasonic frequency on degradation rate constants were not investigated quantitatively. In this study, the degradation process of a model for hazardous organic compound methylene blue was investigated using ultrasonic irradiation. The study focused on the effects of ultrasonic frequency and ultrasonic power on the degradation rate constant. The apparent degradation rate constants were estimated based on time dependence of methylene blue concentration assuming pseudo-first-order kinetics for the decomposition. A linear relationship between the apparent degradation rate constant and ultrasonic power was identified. In addition, the apparent degradation rate constants at frequencies of 127 and 490 kHz were much larger than those at 22.8 kHz. A relationship between the apparent degradation rate constant and the sonochemical efficiency value (SE value) was also found. Based on these results, a simple model for estimating the apparent degradation rate constant of methylene blue based on the ultrasonic power and the SE value is proposed in this study.     

First observation of B(s)(0) → J/ψη and B(s)(0) → J/ψη'

We report first observations of B(s)(0) → J/ψη and B(s)(0) → J/ψη'. The results are obtained from 121.4 fb(-1) of data collected at the Υ(5S) resonance with the Belle detector at the KEKB e+ e- collider. We obtain the branching fractions B(B(s)(0) → J/ψη)=[5.10±0.50(stat)±0.25(syst)(-0.79)(+1.14)(N(B(s)(*) B(s)(*))]×10(-4), and B(B(s)(0) → J/ψη')=[3.71±0.61(stat)±0.18(syst)(-0.57)(+0.83)(N(B(s)(*) B(s)(*))]×10(-4). The ratio of the two branching fractions is measured to be (B(B(s) → J/ψη'))/(B(B(s) → J/ψη))=0.73±0.14(stat)±0.02(syst).