Electrochemical bandgaps of a series of poly-3-<Emphasis Type="Italic">p</Emphasis>-phenylthiophenes

The change of the UV-Vis optical absorption of electropolymerized substituted poly-3-p-X-phenylthiophenes (X = -H, -CH₃, -OCH₃, -COCH₃, -COOC₂H₅, -NO₂) has been followed in situ as a function of applied electrode potential in an electrolyte solution of tetraethylammoniumtetrafluoroborate Et₄NBF₄ in acetonitrile. The UV-Vis spectra show features between 300 and 900 nm similar to those observed with many other polythiophenes having a high degree of conjugation. During stepwise oxidation of the poly-3-p-X-phenylthiophene films, the intensity of the absorption due to the π→π*-transition around 450–566 nm decreases, and a new broad absorption band associated with (bi)polaron states appears around 730–890 nm. On the other hand, during the oxidation (p-doping) of the poly-3-p-X-phenylthiophene films, a blue (hypsochromic) shift is observed for both absorption bands. This is explained by taking into account that a polymer contains a distribution of chain lengths, and the longest polymer chains (the absorption of which occurs at lower energies) start to oxidize at the relatively lowest potentials. The electrochemical bandgaps of poly-3-p-X-phenylthiophenes have been estimated based on results of cyclic voltammetry. Bandgaps obtained this way have been found to be generally higher than optical bandgaps; the actual discrepancy was found to depend on the mode of evaluation. Dedicated to Piero Zanello on the occasion of his 65th birthday in recognition of his numerous contributions to inorganic electrochemistry.

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CAL3JHH: a Java program to calculate the vicinal coupling constants (<Superscript>3</Superscript><Emphasis Type="Italic">J</Emphasis><Subscript>H,H</Subscript>) of organic molecules

Here, we present a free web-accessible application, developed in the JAVA programming language for the calculation of vicinal coupling constant (³ J _H,H) of organic molecules with the H–C_sp3–C_sp3–H fragment. This JAVA applet is oriented to assist chemists in structural and conformational analyses, allowing the user to calculate the averaged ³ J _H,H values among conformers, according to its Boltzmann populations. Thus, the CAL3JHH program uses the Haasnoot–Leeuw–Altona equation, and, by reading the molecule geometry from a protein data bank (PDB) file format or from multiple pdb files, automatically detects all the coupled hydrogens, evaluating the data needed for this equation. Moreover, a “Graphical viewer” menu allows the display of the results on the 3D molecule structure, as well as the plotting of the Newman projection for the couplings. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Superhydrophobic surfaces of microspheres obtained by self-assembly of poly[2-(perfluorooctyl)ethyl acrylate-<Emphasis Type="Italic">ran</Emphasis>-2-(dimethylamino)ethyl acrylate] in supercritical carbon dioxide

Superhydrophobic surfaces were obtained by coating with microspheres formed by the self-assembly of poly[2-(perfluorooctyl)ethyl acrylate-ran-2-(dimethylamino)ethyl acrylate] (P[POA-r-DAA]) in the presence of dicarboxylic acids in supercritical carbon dioxide. The P[POA-r-DAA] random copolymer aggregated into micellar microspheres through the hydrogen bond cross-linking of the amino groups via the carboxylic acids. The size of the microspheres and the amount of the acids needed to produce them were dependent on the kinds of acids. Glutaric acid (Glu) and perfluorosuccinic acid (Psuc) provided microspheres at a 0.5 molar ratio of the acid/DAA. Psuc produced smaller microspheres than Glu. Maleic acid (Ma), succinic acid (Suc), and azelaic acid (Az) required a higher molar ratio to produce the microspheres. These acids provided spherical particles at the ratio of 1.0. The microspheres produced by Suc and Az contained particles with a several hundred nanometer size. The surface coated with the microspheres showed high water contact angles of 164°–172°.

A novel Ce<Superscript>III</Superscript>-cyclam type complex and its redox chemistry in aqueous solutions

A new Ce^III complex was synthesized by mixing the ligand “dioxocyclam” with Ce^III ions at pH 8.0 and its redox properties were investigated.

Mechanism of the electroreduction of Ni (II) ions on mercury electrodes catalyzed by pyridine and its derivatives: nicotinamide, <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diethylnicotinamide and nicotine: concept of parallel heterogeneous catalytic reactions

The theory of the polarographic catalytic currents (mechanism CE) has been developed for the system: Ni²⁺-L-X^p− where L: pyridine (Py), nicotinamide (NA), N,N-diethylnicotinamide (DEN), nicotine (NC) and X^p−: NO⁻ ₃, AcO⁻, HPO²⁻ ₄ . The theory is based on the kinetic parallel heterogeneous catalytic reactions:

Equations describing lamellar structure parameters and melting points of polyethylene-<Emphasis Type="Italic">co</Emphasis>-(butene/octene)s

Time- and temperature-dependent SAXS-experiments were used to determine the effect of octene and butene co-units on the lamellar structure and the melting properties of polyethylene. As expected, melting points decrease with increasing co-unit content, but crystal thicknesses are not affected and depend on the crystallization temperature only. Results can be cast into some simple equations which describe the dependence:

X-ray structural analyses and DFT study of 7-thianorbornenes: 4-aza-4-phenyl-10-thiatricyclo[5.2.1.0.<Superscript>2,6</Superscript>]deca-8-ene-3,5-dione and 4-aza-l,4,7-trimethyl-10-thiatricyclo[5.2.1.0.<Superscript>2,6</Superscript>]deca-8-ene-3,5-dione

X-ray structures of Diels–Alder adducts of thiophene with N-methylmaleimide and 2,5-dimethylthiophene with N-phenylmaleimide were determined and compared to literature data. In addition, quantum chemical calculations at various levels of theory were used to study their molecular and electronic structure. A comparison with experimental results showed that MP2/6-31G^*, HF/6-311+G^** and PBE1PBE/6-31G^* methods give the most accurate structures.

Structure and chromotropic properties of mono- and binuclear mixed-ligand nickel(II) complexes containing 1,3-diketonate and polyamine ligands

Abstract  Mixed-ligand Ni^II complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky ligands on the coordination distances and spectral properties are discussed. Graphical Abstract  

Supramolecular architecture of phenylcarbamoylated acetone oxime 1,1-diisopropyl-3-phenylurea] complex

Carbamoylated oximes 1 form 1:1 molecular complexes 4 with N,N-dialkyl-N′-phenylurea when stirred in THF or ether at room temperature for short time in good yields. The molecular complexes 4a–e were isolated and characterized by analytical and spectral means. X-ray crystallographic analysis for complex 4a was performed. In this paper, we report the use of complex 4a and its moieties as building blocks to form non-interacting polymeric zigzag chains by inter- and intramolecular hydrogen bonds along b-axis, and details of supramolecular architecture of 4a. There is a intramolecular H–H interaction between hydrogen of urea NH and neighboring hydrogen of diisopropyl's CH linked to the other urea nitrogen. In addition, to obtain the most favorable orientation of the moieties of the title complex, PM3 semi-empirical quantum mechanical calculations were performed and then results from X-ray crystallography and computational modeling were compared.

A model for high-surface-area porous Nafion™-bonded cathodes operating in hydrogen–oxygen proton exchange membrane fuel cells (PEMFCs)

A critical discussion of dioxygen reduction kinetics using the Tafel (for the irreversible cathode process) and the Butler–Volmer (anode process) rate equations has been used to evaluate the accuracy of “standard” modeling interpretations of experimental cell potential current (E–I) plots. The potential–current curve for what is believed to be an optimized Nafion™-bonded fuel cell cathode was analyzed. It appears to behave as a well-ordered diffusional system and shows high electrocatalyst utilization based on its electrocatalytic and gas diffusion characteristics. The electrode appears to perform as expected, without any anomalous characteristics showing any lower than expected electrocatalyst utilization. Any improvement in electrode performance, which is certainly desirable, seems to demand an improved diffusional structure, barring any potential (although unlikely) change in electrochemical kinetic characteristics.

Bonding in β-diketiminate boron and its analogues

Bonding analysis in β-diketiminate boron and related systems has been performed. For the optimized geometries (MP2/aug-cc-pVTZ), the post-SCF electron density function has been produced and its topological parameters have been analyzed according to Atoms in Molecules Quantum Theory approach. The B–N bond has characteristics similar to those found for TM–ligand bonding. The symmetric character of the B–N interaction found for the β-diketiminate boron results from the fully π-electron delocalized character of the β-diketiminate moiety. If the π-electron system in NCCCN sequence of bonds is localized, the asymmetric B–N bonding is enforced. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

The Physical and Electronic Structure of M<Subscript>2</Subscript> Quadruply Bonded Complexes: A Density Functional Theory Study

The electronic structures and the physical properties (vertical excitation energies, vibrational stretching frequencies, and bond lengths) of a variety of M–M quadruply bonded (M = Mo, W) complexes are investigated using density functional theory (DFT). By utilizing a variety of pure and hybrid exchange-correlation (XC) functionals and a number basis sets, we are able to recommend a theoretical methodology for most efficiently probing the electronic structures of homoleptic M₂(O₂CR)₄ and bridged M₂(O₂C-X-CO₂)M₂ (R = organic group, typically H; X = conjugated organic group) complexes.

A comparative study of hydrothermal and sol–gel methods in the synthesis of MnO<Subscript>2</Subscript> nanostructures

In this work, MnO₂ nanostructure powders with different crystalline phases have been successfully prepared by hydrothermal and sol–gel methods. The obtained products were characterized by XRD and SEM techniques and their crystallographic phases and morphological properties compared. Results showed that α-MnO₂, β-MnO₂, and δ-MnO₂ nanorods were synthesized by hydrothermal method and γ-MnO₂ polymorph was obtained by sol–gel method.

Synthesis of polystyrene/silica hybrid composites by the sol–gel method: effect of introduction of a flexible component (butyl acrylate) into the silylated polystyrene backbone

Polystyrene/silica, polystyrene–butylacrylate/silica, silylated polystyrene/silica, and silylated polystyrene–butylacrylate/silica hybrid composites were synthesized by the sol–gel method in tetrahydrofuran using HCl as catalyst and tetraethylorthosilicate as the silica precursor. The polymers were characterized by fourier transform infrared (FTIR), nuclear magnetic resonance, and gel permeation chromatography. The sol–gel mixtures were cast on glass plates and dried in air at 30°C for 72 h. The composites were characterized by FTIR, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy analysis. Silica (12.8%) could be incorporated within the silylated polystyrene–butylacrylate matrix while retaining optical transparency. These composites showed better thermal stability and water resistance in comparison to the individual polymers.

Formation of novel 1,3-thiazole- and 1,2-thiazole-fused aporphines and study on the simultaneously occurring benzothiazole–benzisothiazole-type isomerization

Abstract  The synthesis and acid-catalyzed rearrangement of novel thiazolomorphinandienes have been presented. An isomerization was observed simultaneously with the backbone transformation. An extensive study was performed to determine the major effects of the isomerization of 2′-alkyl- and aryl-substituted thiazoloapocodeines into 3′-alkyl- and arylisothiazoloapocodeines. The obtained results provided another practical example of the reversible benzisothiazole–benzothiazole-type isomerization emphasizing the determining role of the thermal effects in the occurrence of these isomerization products. The obtained experimental results and the proposed mechanism were in agreement with the calculated DFT data. Graphical abstract  

The use of LCMS as an analytical tool for hydrolysis/polycondensation monitoring of a chiral ORMOSIL precursor

The kinetic of the sol–gel hydrolysis and polycondensation reactions of a chiral ORMOSIL precursor was investigated by LCMS technique as a function of water excess and pH. While the amount of water does not significantly change the kinetics, the reactions strongly depend on the [H]⁺ concentration. At pH ≤ 3, the hydrolysis is very fast and the conversion of the precursor is completed within less than 1 h whereas at 80% of the precursor is still present after 50 h at pH = 3.5. This kinetic study allows to define a set of initial conditions and time ranges required to provide good optical quality dip coated films .

A fluorous tag-bound fluorescence derivatization reagent, F-trap pyrene, for reagent peak-free HPLC analysis of aliphatic amines

We have developed a novel pre-column fluorescence derivatization reagent for amines, F-trap pyrene. This reagent comprises a fluorescent pyrene moiety, an amine-reactive Marshall linker, and a fluorophilic perfluoroalkyl group known as fluorous tag. When the reagent reacts with aliphatic amines and amino acids to give fluorescent derivatives, the fluorous tag in the reagent is eliminated simultaneously. Therefore, excess unreacted reagents in the derivatization reaction solution still have the fluorous tag and could be removed by fluorous solid-phase extraction selectively before high-performance liquid chromatography (HPLC) analysis. By using this reagent, 13 kinds of aliphatic amine (C₂–C₁₆) derivatives can be separated within 40 min by reversed-phase HPLC with gradient elution. In this chromatogram, unreacted reagents peak at around 28 min, greatly decrease after fluorous solid-phase extraction, and do not interfere with the quantification of each amine. The detection limits (S/N = 3) for examined aliphatic amines are 3.6–25 fmol per 20 μL injection. We have also applied this reagent successfully to the amino acid analysis.

Encapsulating of single quantum dots into polymer particles

Single semiconductor quantum dots were embedded into polymer particles with diameters below 0.1 μm by an emulsion polymerization procedure or via a secondary dispersion approach. The photoluminescence properties of the nanocrystals are retained upon encapsulation, as demonstrated by fluorescence confocal microscopy.

Cytocompatibility of surface ground PE doped with calcium salt of 6-carboxycellulose

We studied the physical–chemical properties of polyethylene (PE) films doped with calcium salt of 6-carboxycellulose (Ca-oxy) in concentrations 0–20 wt.% and their interactions with cells. The interaction between the PE/Ca-oxy composite film and 3T3 cells has not been described so far. Modification by surface grinding to enhance material cytocompatibility was studied. The surface wettability of doped films was tested by contact angle measurements and the surface morphology by SEM microscopy and profilometry. Adhesion and proliferation of tissue cells (3T3 mouse fibroblasts) were studied in vitro on pristine and ground doped PE films. The ground samples have a higher contact angle values and the number of proliferated cells is greater on the ground samples than on pristine ones. The presence of Ca-oxy in PE film increases the adhesion of 3T3 cells on the doped substrate and on ground samples adhere more cells than on pristine ones.

Label-free detection of the aptamer binding on protein patterns using Kelvin probe force microscopy (KPFM)

Anti-lysozyme aptamers are found to preferentially bind to the edge of a tightly packed lysozyme pattern. Such edge-binding is due to the better accessibility and flexibility of the edge lysozyme molecules. Kelvin probe force microscopy (KPFM) was used to study the aptamer–lysozyme binding. Our results show that KPFM is capable of detecting the aptamer–protein binding down to the 30 nm scale. The surface potential of the aptamer–lysozyme complex is approximately 12 mV lower than that of the lysozyme. The surface potential images of the aptamer-bound lysozyme patterns have the characteristic shoulder steps around the pattern edge, which is much wider than that of a clean lysozyme pattern. These results demonstrate the potentials of KPFM as a label-free method for the detection of protein–DNA interactions. Figure Aptamers preferentially bind on the edge of a protein pattern as revealed by Kelvin force microscopy.