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41.
The S-H bond dissociation enthalpies [BDE(S-H)] of a set of 5-X- and 6-X-3-pyridinethiols (X = F, Cl, CH3, OCH3, NH2, N(CH3)2, CF3, CN, and NO2) have been computed using the density functional theory based (RO)B3LYP procedure with 6-311++G(2df,2p) basis set. The effects of substituents on the BDE(S-H), proton affinity of the pyridinethiol anion [PA(S-)] and ionization energy (IE) are analyzed and their correlations with Hammett's substituent constants are examined. Subsequently, a series of 6-substituted 3-pyridinethiols have been explored to find out their antioxidant potentials. Finally, a number of 3-pyridinethiol based compounds are theoretically proposed as novel antioxidants. 相似文献
42.
Soaram Kim Hyunggil Park Giwoong Nam Hyunsik Yoon Jae-Young Leem 《Journal of Sol-Gel Science and Technology》2013,67(3):580-591
Sol–gel spin-coating was used to grow zinc oxide (ZnO) thin films doped with 0–2.5 at.% B on quartz substrates. The structural, optical, and electrical properties of the thin films were investigated using field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), ultraviolet–visible spectroscopy, and van der Pauw Hall-effect measurements. All the thin films had deposited well onto the quartz substrates and exhibited granular morphology. The average crystallite size, lattice constants, residual stress, and lengths of the bonds in the crystal lattice of the thin films were calculated from the XRD data. The PL spectra showed near-band-edge (NBE) and deep-level emissions, and B doping varied the PL properties and increased the efficiency of the NBE emission. The optical transmittance spectra for the undoped ZnO and boron-doped zinc oxide (BZO) thin films show that the optical transmittance of the BZO thin films was significantly higher than that of the undoped ZnO thin films in the visible region of the spectra and that the absorption edge of the BZO thin films was blue-shifted. In addition, doping the ZnO thin films with B significantly varied the absorption coefficient, optical band gap, Urbach energy, refractive index, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator strength, average oscillator wavelength, dielectric constant, and optical conductivity of the BZO thin films. The Hall-effect data suggested that B doping also improved the electrical properties such as the carrier concentration, mobility, and resistivity of the thin films. 相似文献
43.
The reaction of ninhydrin with 1,2,3- and 1,2,4-trimethylbenzene in the presence of H2SO4 or AlCl3 afforded 2-monoaryl and 2,2-diaryl-1,3-indanedione derivatives as the major products. With 1,3,5-trimethylbenzene as the arene nucleophile, either a reduction product or an indenoindanone derivative was obtained depending upon the catalyst employed in the reaction. 相似文献
44.
Young Chul Kim Jun Young Lee Dong Young Kim Hyun Nam Cho Chung Yup Kim 《Macromolecular Symposia》1997,118(1):461-466
The optical transmittance of the film spin-cast from the polypyrrole(PPy) solution in chloroform depended on the thickness of the film. The film with 80% transmittance showed a surface resistivity of 23kΩ/□. A TN-LCD cell with rubbed PPy films as the LC alignment layers responded properly to an applied potential of 3.0V. Reflective mode cholesteric LCD cells made with black PPy film electrodes responded to AC fields to switch between the planar and focal conic states. PPy with imine structures introduced by deprotonation of doped PPy with NaOH solution was used as a diode material to exhibit a photo-current on exposing to light. 相似文献
45.
Cho KB Kim EJ Seo MS Shaik S Nam W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(33):10444-10453
The experimentally measured bimolecular reaction rate constant, k(2) , should in principle correlate with the theoretically calculated rate-limiting free energy barrier, ΔG(≠) , through the Eyring equation, but it fails quite often to do so due to the inability of current computational methods to account in a precise manner for all the factors contributing to ΔG(≠) . This is further aggravated by the exponential sensitivity of the Eyring equation to these factors. We have taken herein a pragmatic approach for C?H activation reactions of 1,4-cyclohexadiene with a variety of octahedral nonheme Fe(IV) O complexes. The approach consists of empirically determining two constants that would aid in predicting experimental k(2) values uniformly from theoretically calculated electronic energy (ΔE(≠) ) values. Shown in this study is the predictive power as well as insights into energy relationships in Fe(IV) O C?H activation reactions. We also find that the difference between ΔG(≠) and ΔE(≠) converges at slow reactions, in a manner suggestive of changes in the importance of the triplet spin state weight in the overall reaction. 相似文献
46.
Pure separation and sorting of microparticles from complex fluids are essential for biochemical analyses and clinical diagnostics. However, conventional techniques require highly complex and expensive labeling processes for high purity separation. In this study, we present a simple and label-free method for separating microparticles with high purity using the elasto-inertial characteristic of a non-Newtonian fluid in microchannel flow. At the inlet, particle-containing sample flow was pushed toward the side walls by introducing sheath fluid from the center inlet. Particles of 1 μm and 5 μm in diameter, which were suspended in viscoelastic fluid, were successfully separated in the outlet channels: larger particles were notably focused on the centerline of the channel at the outlet, while smaller particles continued flowing along the side walls with minimal lateral migration towards the centerline. The same technique was further applied to separate platelets from diluted whole blood. Through cytometric analysis, we obtained a purity of collected platelets of close to 99.9%. Conclusively, our microparticle separation technique using elasto-inertial forces in non-Newtonian fluid is an effective method for separating and collecting microparticles on the basis of size differences with high purity. 相似文献
47.
48.
Rücktitelbild: Cofactor‐Free Light‐Driven Whole‐Cell Cytochrome P450 Catalysis (Angew. Chem. 3/2015)
49.
G.?A.?Mun I.?K.?Nam R.?R.?SarsengalievEmail author Z.?S.?Nurkeeva P.?I.?Urkimbaeva K.?Park 《Colloid and polymer science》2004,282(10):1111-1117
Amphiphilic hydrogels of copolymers of the vinyl ether of ethylene glycol and vinyl isobutyl ether were synthesized by -radiation-induced free radical polymerization. Hydrogels with certain copolymer compositions showed thermo-sensitive behavior in aqueous solutions. The swelling behavior of the hydrogels in cetylpyridinium bromide aqueous solution was studied. Increased swelling of the hydrogels was observed in the surfactant solutions. The increased swelling was more prominent for the hydrogels with a higher content of hydrophobic moiety in the copolymer composition, and with higher surfactant concentration. The reason for this phenomenon is discussed. Treatment of some hydrogels in the surfactant solutions resulted in higher swelling ability in distilled water with distinct thermo-induced contraction over a narrow temperature interval. 相似文献
50.
Tuning the Redox Properties of a Nonheme Iron(III)–Peroxo Complex Binding Redox‐Inactive Zinc Ions by Water Molecules 下载免费PDF全文
Dr. Yong‐Min Lee Suhee Bang Heejung Yoon Seong Hee Bae Dr. Seungwoo Hong Dr. Kyung‐Bin Cho Dr. Ritimukta Sarangi Prof. Dr. Shunichi Fukuzumi Prof. Dr. Wonwoo Nam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10676-10680
Redox‐inactive metal ions play important roles in tuning chemical properties of metal–oxygen intermediates. Herein we report the effect of water molecules on the redox properties of a nonheme iron(III)–peroxo complex binding redox‐inactive metal ions. The coordination of two water molecules to a Zn2+ ion in (TMC)FeIII‐(O2)‐Zn(CF3SO3)2 ( 1 ‐Zn2+) decreases the Lewis acidity of the Zn2+ ion, resulting in the decrease of the one‐electron oxidation and reduction potentials of 1 ‐Zn2+. This further changes the reactivities of 1 ‐Zn2+ in oxidation and reduction reactions; no reaction occurred upon addition of an oxidant (e.g., cerium(IV) ammonium nitrate (CAN)) to 1 ‐Zn2+, whereas 1 ‐Zn2+ coordinating two water molecules, (TMC)FeIII‐(O2)‐Zn(CF3SO3)2‐(OH2)2 [ 1 ‐Zn2+‐(OH2)2], releases the O2 unit in the oxidation reaction. In the reduction reactions, 1 ‐Zn2+ was converted to its corresponding iron(IV)–oxo species upon addition of a reductant (e.g., a ferrocene derivative), whereas such a reaction occurred at a much slower rate in the case of 1 ‐Zn2+‐(OH2)2. The present results provide the first biomimetic example showing that water molecules at the active sites of metalloenzymes may participate in tuning the redox properties of metal–oxygen intermediates. 相似文献