Synthesis and characterization of an ionic conjugated polymer: Poly[2‐ethynyl‐N‐(2‐thiophenecarbonyl) pyridinium chloride]

The activated polymerization of 2‐ethynylpyridine by using 2‐thiophenecarbonyl chloride yielded the corresponding conjugated ionic polymer, poly[2‐ethynyl‐N‐(2‐thiophenecarbonyl)pyridinium chloride] (PETCPC). The polymerization proceeded well to give high yield of polymer without any additional initiator or catalyst. The instrumental analysis data on polymer structure indicated that the present ionic polymer have a conjugated polymer backbone system having N‐(2‐thiophenecarbonyl)pyridinium chloride as substituents. The photoluminescence maximum peak of PETCPC was located at 573 nm, which corresponds to the photon energy of 2.16 eV. The aromatic functional substituents in the conjugated backbone system shift PL maximum values because it makes different molecule arrangement. The cyclovoltamograms of PETCPC exhibited the electrochemically stable window at ?1.24 to 1.80 V region. It was found that the kinetics of the redox process of polymer might be controlled by the reactant diffusion process from the experiment of the oxidation current density of polymer versus the scan rate. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6153–6162, 2009     

Surface oxides of the oxygen-copper system: Precursors to the bulk oxide phase?

To gain an initial understanding of the copper-based catalysts in commercially important chemical reactions such as the oxygen-assisted water-gas shift reaction, we performed density-functional theory calculations, investigating the interaction of oxygen and copper, focusing on the relative stability of surface oxides and oxide surfaces of the O/Cu system. By employing the technique of “ab initio atomistic thermodynamics”, we show that surface oxides are only metastable at relevant pressures and temperatures of technical catalysis, with no stable chemisorption phase observed even at very low coverage. Although exhibiting only metastability, these surface oxides resemble the bulk oxide material both geometrically and electronically, and may serve as a precursor phase before onset of the bulk oxide phase. Having identified the bulk oxide as the most stable phase under realistic catalytic conditions, we show that a Cu₂O(1 1 1) surface with Cu vacancies has a lower free energy than the stoichiometric surface for the considered range of oxygen chemical potential and could be catalytically relevant.     

Molecular dynamics simulation study on a monolayer of half [2]rotaxane self-assembled on Au(111)

The self-assembled monolayer (SAM) structure of the tetrathiafulvalene-side half of the Stoddart-Heath type [2]rotaxane on Au(111) surface was investigated using molecular dynamics (MD) simulations. We find that the orientation of the cyclobis(paraquat-p-phenylene) (CBPQT) ring depends dramatically on the coverage, changing in order to obtain highly packed SAMs. The ring lies with its large hollow parallel to the surface at lower coverage (up to one CBPQT per 27 surface Au atoms with a footprint of 1.9 nm(2); 1/27) when free space is available around it, but as the coverage increases (up to one CBPQT per 12 surface Au atoms with a footprint of 0.9 nm(2); 1/12), it tilts completely around its axis and lies with its smaller side (paraquat or phenyl ring) parallel to the surface to accommodate the reduced area available. We find that the best packing densities correspond to one CBPQT per 12-18 surface Au atoms (1/18-1/12) with footprints in the range between 0.9 nm(2) and 1.3 nm(2).     

Pyrazolidine derivatives with heteroaryl urea as dipeptidyl peptidase IV inhibitors

In the continuation of efforts to modify the structure of our novel DP-IV inhibitors, a series of pyrazolidine derivatives with heteroaryl urea was synthesized and evaluated for their ability to inhibit dipeptidyl peptidase IV (DP-IV).     

Intramolecular interactions and spin–lattice relaxation times of methyl groups

The carbon T₁ values of the alkyl substituents of various compounds have been measured. The salient observation is that the terminal methyl carbon of the n-propyl or a three-carbon chain bonded to an electronegative atom X(or an electron-donating group) has a reduced T₁ value. A net attractive interaction between the methyl hydrogen atoms and X in the gauche conformation is invoked to account for the observed result. In chains longer than three carbons that are not firmly anchored at one end, the γ steric interaction is suggested to be the main steric interaction that causes the reduced T₁ value observed for the terminal methyl carbon.     

Synthesis and characterization of stable blue light‐emitting poly(spirobifluorene) derivatives containing alkoxy group

Polymers containing alkoxy‐substituted spirobifluorene have been prepared from nickel(0)‐mediated coupling or palladium‐catalyzed Suzuki coupling. The polymers were characterized using various spectroscopies, such as ¹H‐NMR, FT‐IR, and elemental analysis. The high glass transition temperature and high decomposition temperature suggested that the resulting polymers possessed a high thermal stability. The obtained polymers possessed weight average molecular weight of 4500–33,000 with polydispersity index of 1.1–1.9 and good solubility. The low onsets of the oxidation potential suggested that the polymers containing alkoxy substituted spirobifluorene possessed a good hole injection property. The photoluminescence and electroluminescence of the polymers containing alkoxy substituted spirobifluorene showed stable blue color by suppressing the excimer formation due to intermolecular interaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2316–2324, 2005     

An algorithm for the zeros of transcendental functions

Summary In this paper, we extend the dual form of the generalized algorithm of Sebastião e Silva [3] for polynomial zeros and show that it is effective for finding zeros of transcendental functions in a circle of analyticity.     

Benzene-templated hydrothermal synthesis of metal-organic frameworks with selective sorption properties

In this paper, we report two metal-organic frameworks [Co3(ndc)3(bipyen)(1.5)]H2O (1) and [Co2(ndc)2bipyen)]C6H6.H2O (2) (bipyen=trans-1,2-bis(4-pyridyl)ethylene, H2ndc=2,6-naphthalenedicarboxylic acid). These compounds were both synthesized from identical hydrothermal reaction conditions except that benzene was added to the reaction for 2. Crystal structures show that the two compounds have triply interpenetrated three-dimensional frameworks and these frameworks have the same primary structure of a two-dimensional network of interconnected [Co2(O2CR)(4/2)] (R=naphthalene group) paddle-wheels and bridging bipyen ligands. Both compounds have guest water molecules and, in addition, 2 has guest benzene molecules. Structural transformations of the host accompanied guest removal, which can be monitored by powder X-ray diffraction. N2 adsorption data of 2 show that there are two different types of pores corresponding to the benzene and water pores. Upon exposure to vapors of several organic molecules, the heat-treated sample of 2 adsorbs benzene and cyclohexene, but does not adsorb toluene, (o-, m-, and p-)xylenes, cycloheptatriene, or cyclohexane.