Near-IR Luminescent YbIII Coordination Polymers Composed of Pyrene Derivatives for Thermostable Oxygen Sensors

Oxygen-sensitive and near-infrared (NIR) luminescent Yb^III coordination polymers incorporating ligands based on pyrene derivatives were synthesized: Yb^III–TBAPy and Yb^III–TIAPy (TBAPy: 1,3,6,8-tetrakis(p-benzoate)pyrene; TIAPy: 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene). The coordination structures of these materials have been characterized by means of electrospray ionization mass spectrometry, X-ray diffraction analysis, and thermogravimetric analysis. Moreover, the porous structure of Yb^III–TIAPy has been evaluated by measuring its N₂ adsorption isotherm. The NIR luminescence properties of Yb^III–TBAPy and Yb^III–TIAPy have been examined by acquiring emission spectra and determining emission lifetimes under air or argon and in vacuo. Yb^III–TIAPy exhibited high thermal stability (with a decomposition temperature of 400 °C), intense luminescence (with an emission quantum yield under argon of 6.6 %), and effective oxygen-sensing characteristics. These results suggest that NIR luminescent Yb^III coordination polymers prepared using pyrene derivatives could have applications in novel thermo-stable oxygen sensors.     

Comparison of the compact dry TC method with the standard pour plate method (AOAC official method 966.23) for determining aerobic colony counts in food samples: Performance-tested method

Compact Dry TC qualifies as a rapid method kit for determining aerobic colony counts in foods. The plates are presterilized and contain culture medium and a cold-soluble gelling agent. The medium is rehydrated by inoculating 1 mL diluted sample into the center of the self-diffusible medium and allowing the solution to diffuse by capillary action. The plates can then be incubated and the colonies counted without any additional steps. The Compact Dry TC method was validated with 5 different raw meats. The performance tests were conducted at 35 degrees and 30 degrees C. In all required performance studies, no apparent differences were observed between the Compact Dry TC method and the Standard Pour Plate method (AOAC Official Method 966.23) for the detection level of aerobic microorganisms. For the accuracy claim (n = 60), a correlation factor of r2(35) = 0.9977 (35 degrees C) and r2(30) = 0.9932 (30 degrees C) could be assigned, as stated in the application for "Performance Tested Method." Quality consistency and storage robustness studies, showed no significant variations in plate count results with different production lots or plates of diverse storage age.     

New features in the catalytic cycle of cytochrome P450 during the formation of compound I from compound 0

Density functional theory (DFT) is applied to the dark section of the catalytic cycle of the enzyme cytochrome P450, namely, the formation of the active species, Compound I (Cpd I), from the ferric-hydroperoxide species (Cpd 0) by a protonation-assisted mechanism. The chosen 96-atom model includes the key functionalities deduced from experiment: Asp(251), Thr(252), Glu(366), and the water channels that relay the protons. The DFT model calculations show that (a) Cpd I is not formed spontaneously from Cpd 0 by direct protonation, nor is the process very exothermic. The process is virtually thermoneutral and involves a significant barrier such that formation of Cpd I is not facile on this route. (b) Along the protonation pathway, there exists an intermediate, a protonated Cpd 0, which is a potent oxidant since it is a ferric complex of water oxide. Preliminary quantum mechanical/molecular mechanical calculations confirm that Cpd 0 and Cpd I are of similar energy for the chosen model and that protonated Cpd 0 may exist as an unstable intermediate. The paper also addresses the essential role of Thr(252) as a hydrogen-bond acceptor (in accord with mutation studies of the OH group to OMe).     

New sesquiterpene lactones from water extract of the root of Lindera strychnifolia with cytotoxicity against the human small cell lung cancer cell, SBC-3

In the present study, new sesquiterpene lactones (1) and (2) were isolated from the EtOAc soluble fraction of the water extract of Linderae Radix through bioassay-guided fractionation and isolation methods. The structure of these compounds was elucidated by spectroscopic analysis of their 2D NMR spectra, including COSY, HMBC, and HMQC techniques. Two isolates showed significant cytotoxicity against the human small cell lung cancer cell SBC-3, and lesser cytotoxicity against mouse fibroblast cell 3T3-L1.     

Furopyridines. XXX. Synthesis and reaction of difuro[3,2-c:- 3′,2′-e]pyridine,a new tricyclic heterocycle

Difuro[3,2-c:3′,2′-e]pyridine 1 , a new tricyclic heteroaromatic, has been prepared for the first time. Bromination of 1 with molecular bromine gave 3-bromo 7 , 8-bromo 7′ and 3,8-dibromo derivative 8 ; nitration with fuming nitric acid yielded 2-nitro compound 9 , while nitration with a mixture of fuming nitric acid and sulfuric acid gave 2,7-dinitro derivative 10 ; formylation with n-butyllithium and dimethylformamide gave 2-formyl 11 , 7-formyl 11′ , and 2,7-diformyl compound 12. The N-oxide 14 of 1 afforded 4-cyano compound 15 by cyanation with trimethylsilyl cyanide, 4-chloro compound 16 by chlorination with phosphorus oxychloride, and 4-acetoxyl compound 17 by acetoxylation with acetic anhydride.     

Investigation on the arrangement of lithium ions in LixLa(1/3)NbO3 with perovskite structure

The relationship between the Li arrangement and the electrochemical behavior has been examined as a function of composition x in electrochemically lithiated A-site deficient perovskite, Li(x)()La(1/3)NbO(3). The cell potential diagram and powder X-ray diffraction (XRD) study indicated that the Li ions are inserted into the vacant Perovskite A-site with an electrochemical reaction. In addition, the derivatives of the cell potential diagram showed three cathodic peaks, indicating a stepwise Li insertion mechanism takes place. Such a stepwise behavior would be ascribed to the changes in arrangement of inserted Li ions in the Perovskite lattice, since the XRD patterns of pristine La(1/3)NbO(3) showed that the La arrangement in La(1/3)NbO(3) was ordered along the c-axis, causing two kinds of A-site vacancies. To reveal the changes in the arrangement of Li ions, the entropy measurement of the reaction was performed by both the electrochemical and the calorimetric techniques. Moreover, the formation energy of the Perovskite structure with various Li arrangements was compared by using an ab initio calculation. The results of experiment and computation suggested that the electrochemical reaction proceeded via two kinds of superstructures of Li(1/6)La(1/3)NbO(3) and Li(1/2)La(1/3)NbO(3) due to the ordered arrangement of Li ions.     

Uranium oligomerization in chloride-based high temperature melts: in situ XAS studies

In situ EXAFS spectroscopic studies of uranium compounds in high temperature alkali chloride melts indicate the presence of oligomeric species. An investigation into UCl(3) and UCl(4) dissolved in LiCl reveals long range ordering of uranium atoms in the molten state which is not maintained on quenching. Studies of uranium dioxide dissolved in LiCl-KCl eutectic with HCl exhibit long range ordering in both molten and quenched states, and the EXAFS data can be modeled using multiple coordination shells.     

Origin of visible-light-driven photocatalysis: A comparative study on N/F-doped and N-F-codoped TiO2 powders by means of experimental characterizations and theoretical calculations

An overall comparative study was carried out on N-doped, F-doped, and N-F-codoped TiO₂ powders (NTO, FTO, NFTO) synthesized by spray pyrolysis in order to elucidate the origin of their visible-light-driven photocatalysis. The comparisons in their experimentally obtained characteristics were based on the analysis of XPS, UV-Vis, PL, NH₃-TPD and ESR spectra. The comparisons in their theoretically predicted properties were based on the analysis of the calculated electronic structures. As the results, N-doping into TiO₂ resulted in not only the improvement in visible-light absorption but also the creation of surface oxygen vacancies. F-doping produced several beneficial effects including the creation of surface oxygen vacancies, the enhancement of surface acidity and the increase of Ti³⁺ ions. Doped N atoms formed a localized energy state above the valence band of TiO₂, whereas doped F atoms themselves had no influence on the band structure. The photocatalytic tests indicated that the NFTO demonstrated the highest visible-light activity for decompositions of both acetaldehyde and trichloroethylene. This high activity was ascribed to a synergetic consequence of several beneficial effects induced by the N-F-codoping.     

Monomer-isomerization polymerization. XXIII.. Monomer-isomerization polymerization of 5-phenyl-2-pentene with ziegler–natta catalysts

5-Phenyl-2-pentene (5Ph2P) was found to undergo monomer-isomerization polymerization with TiCl₃–R₃Al (R = C₂H₅ or i-C₄H₉, Al/Ti > 2) catalysts to give a polymer consisting of exclusively 5-phenyl-1-pentene (5Ph1P) unit. The geometric and positional isomerizations of 5Ph2P to its terminal and other internal isomers were observed to occur during polymerization. The catalyst activity of alkylaluminum examined to TiCl₃ was in the following order: (C₂H₅)₃Al > (i-C₄H₉)₃Al > (C₂H₅)₂AlCl. The rate of monomer-isomerization polymerization of 5Ph2P with TiCl₃–(C₂H₅)₃Al catalyst was influenced by both the Al/Ti molar ratio and the addition of nickel acetylacetonate [Ni(acac)₂], and the maximum rate was observed at Al/Ti = 2.0 and Ni/Ti = 0.4 in molar ratios.