Alloyed Tetranuclear Metal Chains of Pd4−nPtn (n=0–3) Scaffolded by a New Linear Tetraphosphine Containing a PNP Bridge

A new linear tetraphosphine containing a PNP phosphazane bridge, rac-bis[(diphenylphosphinomethyl)phenylphosphino]phenylamine (rac-dpmppan), was synthesized and utilized to support a series of Pd/Pt mixed metal tetranuclear chains, [Pd_4−nPt_n(μ-rac-dpmppan)₂(XylNC)₂](PF₆)₂ (XylNC=xylyl isocyanide; n=0: Pd₄ ( 1 ), 1: PtPd₃ ( 2 ), 2: PtPd₂Pt ( 3 ), 2: Pt₂Pd₂ ( 4 ), 3: Pt₂PdPt ( 5 )), in which the number and positions of additional Pt atoms were successfully controlled depending on the respective synthetic procedures using transformations from 1 to 3 through 2 and from 4 to 5 by redox-coupled exchange reactions. The ³¹P{¹H} NMR and ESI mass spectra and X-ray diffraction analyses revealed almost identical tetranuclear structures, with slight contraction of metal-metal bonds according to incorporation of Pt atoms. The electronic absorption spectra of 1 – 5 exhibited characteristic bands at 635–510 nm with an energy propensity depending on the number and positions of Pt centres, which were assigned to HOMO (dσ*σσ*) to LUMO (dσ*σ*σ*) transition by theoretical calculations. The present results demonstrated that the electronic structures of Pd/Pt mixed-metal tetranuclear complexes are finely tuned as orbital-overlapping alloyed metal chains by atomically precise Pt incorporation in the Pd₄ chain.     

Analyzing censored data in the analysis of multiplicative repeatability and reproducibility studies

Measurements from instruments are sometimes censored at or below the instrument’s lower or upper limit of detection because the instruments have a calibrated response only over a certain data range. Near the ends of the range, the system reports a censored value such as “measurand value is less than threshold,” or “measurand value is more than threshold.” How should one analyze data that includes such “less than” and/or “more than” results and what is the impact of such censoring on estimation of variance components? To answer these two questions, this article makes three contributions: (1) It illustrates a straightforward numerical Bayesian analysis of such censored data based on the likelihood function, (2) it provides a simulation study to show the impact of increased amounts of censoring, and (3) it shows that if the true likelihood has an unknown form for measurand values near the threshold and another known form away from the threshold, then it is prudent for the measurement system to report censored values rather than actual values. Open source software to analyze censored data is provided as supplementary material.     

15-deoxy-isoxeniolide-A,new diterpenoid from a bornean soft coral,Xenia sp.

A new xenicane diterpenoid, 15-deoxy-isoxeniolide-A (1) along with four known compounds 9-deoxy-isoxeniolide-A (2), isoxeniolide-A (3), xeniolide-A (4) and coraxeniolide-B (5) were isolated from the Bornean soft coral Xenia sp. The structures of these metabolites were elucidated on the basis of spectral analysis, NMR and HRESIMS. Compound 5 showed cytotoxic activity against ATL cell line, S1T.     

Experimental and theoretical approaches to the study of the reactivity and mechanism of the substitution of phenyl 1-(2,4-dinitronaphthyl) ether with anilines derivatives

Reactions of aniline derivatives in dimethyl sulfoxide with phenyl 1-(2,4-dinitronaphthyl) ether yield aryl 1-(2,4-dinitronaphthyl) amine, which results in substitution of the phenoxy groups at the naphthyl ipso carbon atom. Rate constants were measured spectrophotometrically, and reaction proton transfer was rate limiting. The values of the rate coefficients indicate a rate-limiting proton transfer mechanism with significant substituent effects. The calculated activation parameters were of regular variation with substituents in 4- and 3-position in the aniline nucleophile, and the reaction proceeded through a common mechanism. Hammett's reaction constant showed that the reaction rate constants depend on the electron density of the nitrogen atom of aniline derivative, whereas the coefficient value obtained from the Brönsted relation indicated that the reaction was significantly associative and quite zwitterion like. Computational studies of the substitution were carried out based on density functional theory, and theoretical to the experimental agreement was achieved.     

Chiral Dinuclear EuIII,TbIII, and YIII Complexes Supported by P-Stereogenic Linear Tetraphosphine Tetraoxide

A P-stereogenic linear tetraphosphine tetraoxide, (R,R)- or (S,S)-dpmppm(=O)₄, was synthesized to prepare C₂ dinuclear M(hfa)₃ complexes (M=Eu, Tb, Y) as the first example of lanthanide(III) complexes with P-chiral multidentate phosphine oxides. The mononuclear M(hfa)₃ complexes (M=Eu, Y) with a P-chiral diphosphine dioxide, tpdpb(=O)₂, were also prepared, and comparison of their photophysical properties for the Eu^III complexes revealed that significant chiral induction from the P-chiral centers arises on the achiral M(hfa)₃ units through intramolecular π-π stacking constraint in the dinuclear system.     

Alkane Shape- and Size-Recognized Selective Vapor Sorption in “Channel-Like” Crystals Based on Thiacalixarene Assemblies

Alkanes composed of C−C and C−H show a low electric polarization, and therefore, there is only very weak interaction between alkanes and adsorbents. Thus, it is difficult to separate a specific alkane from a mixture of alkanes by adsorption. Here, two activated “channel-like” crystals generated from brominated thiacalix[4]arene propyl ethers, which adopt 1,3-alternate and partial cone conformations, recognize specific alkane vapors depending on alkane-shape and -size, sorting in three-type alkane guests such as linear, branched, and cyclic alkanes. Two activated crystals, which are prepared by removal of solvent upon heating under reduced pressure, incorporate branched and/or cyclic alkane vapors by a unique “gate-opening” mechanism via a crystal transformation in the process. Linear alkane vapors do not trigger gate opening and are not taken up by the activated crystals. The shape and size molecular-recognition properties of the activated crystals promises considerable usefulness for the separation of linear, branched, and cyclic alkanes.     

Baryogenesis in false vacuum

The null result in the LHC may indicate that the standard model is not drastically modified up to very high scales, such as the GUT/string scale. Having this in the mind, we suggest a novel leptogenesis scenario realized in the false vacuum of the Higgs field. If the Higgs field develops a large vacuum expectation value in the early universe, a lepton number violating process is enhanced, which we use for baryogenesis. To demonstrate the scenario, several models are discussed. For example, we show that the observed baryon asymmetry is successfully generated in the standard model with higher-dimensional operators.     

Synthesis and spectroscopic characterization of indomethacin-Cd(II), Ce(III), and Th(IV) complexes: IR, 1H NMR,thermal, and biological studies

Solid complexes have been prepared and characterized by IR, UV-Vis, elemental analysis, and ¹H NMR. Indomethacin forms complexes with Cd(II), Ce(III), and Th(IV) ions in molar ratios (ligand: metal) (2: 1), (3: 1), and (4: 1), respectively. The IR spectra of the complexes suggest that the Indomethacin behaves as a monobasic monodentate ligand coordinated to the metal ions via the deprotonated carboxylate group. Prepared complexes exhibit higher antimicrobial activity against several microorganisms, compared to free ligand.