Dynamic quenching of 5-(2′-ethyl-hexyloxy)-p-phenylene vinylene (MEH-PPV) by charge transfer to a C60 derivative in solution

The fluorescence of 5-(2′-ethyl-hexyloxy)-p-phenylene vinylene (MEH-PPV) quenched in solution in 1,2-dichlorobenzene by a soluble derivative of C₆₀ [1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C₆₁; [6,6]PCBM] is studied by changing the concentration of the quencher and by varying the temperature. For MEH-PPV and PCBM dissolved in 1,2-dichlorobenzene, the Stern–Volmer constant (K_SV) is 2 × 10³M⁻¹. At high temperature, K_SV is enhanced because thermal energy facilitates the diffusion of PCBM. The results show that dynamic quenching (rather than static quenching) is the basic mechanism. Comparison with data obtained from quenching studies of trans-stilbene indicates that a single acceptor in contact with an MEH-PPV macromolecule quenches the luminescence from hundreds of repeat units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2553–2557, 2001     

Electrorheological properties of poly[N,N′-(2-amino-5-carboxybutyl-1,3-phenylenedimethylene)-2,2′-diamino-4,4′-bithiazole]

Poly[N,N′-(2-amino-5-carboxybutyl-1,3-phenylenedimethylene)-2,2′-diamino-4,4′-bithiazole] was synthesized and characterized with Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Anhydrous electrorheological (ER) fluids were prepared using the polymer particles as disperse phase and bromodiphenylmethane as a disperse medium. Rheological measurements were carried out via a rotational rheometer to investigate the effects of electric field strength and the polymer particle content on the ER properties. Results indicate that suspensions of the polymer particles containing amino and carboxybutyl groups in bromodiphenylmethane exhibit a substantial ER effect.     

Synthesis and Characterization of the Luminescent Poly[2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl)-1,4-phenylenevinylene]

A new soluble luminescent poly[2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl)-1,4-phenylenevinylene] (DBDP-PPV) is prepared by the dehydrohalogenation of 1,4-bis(bromomethyl)-2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl) benzene (as monomer) in this study. The above monomer bearing decyloxy and 2′,5′-bis(decyloxy)phenyl substituents was prepared via such chemical reactions as alkylation, bromination, and Suzuki coupling reactions. The two asymmetric substituents on the phenylene ring make the DBDP-PPV soluble in organic solvents and eliminate the tolan-bis-benzyl (TBB) structure defects. The structure and properties of the DBDP-PPV are examined by ¹H-NMR, FT-IR, UV/Vis, TGA, photoluminescence (PL), and electroluminescence (EL) analyses. The DBDP-PPV film exhibits a PL peak at 519 nm. With the DBDP-PPV acting as a light-emitting polymer, a device is fabricated with a sequential lamination of ITO/PEDOT/DBDP-PPV/Ca/Ag. The EL spectrum of the device shows a maximum emission at 507 nm. The turn on voltage of the device is about 15.6 V. Its maximum brightness is 4.67 cd/m² at a voltage of 16.8 V.     

The novel preparation method of thermochromic VO2 films with a low phase transition temperature by thermal oxidation of V–Mo cosputtered alloy films

Vanadium dioxide (VO₂) has been studied extensively for its unique insulator-metal transition characteristics and potential applications in thermochromic smart windows, switching devices, and infrared detectors. However, how to balance the metal-insulator transition temperature, luminous transmittance (T_lum) and solar modulation ability (ΔT_sol) of VO₂ thin films remains a challenge. In this work, high-quality thermochromic VO₂ thin films were prepared by a two-step method of magnetron sputtering and thermal oxidation annealing. Metallic and alloyed V–Mo layers were first deposited by direct-current reactive magnetron sputtering, and then a thermal oxidation annealing process was used to obtain pure and Mo-doped VO₂ thin films. The Mo content in the films was regulated by changing the sputtering power of the vanadium target, and the effect of Mo doping on the crystallinity, microstructure, phase transition temperature and optical properties of VO₂ thin films was studied. The shift of the VO₂(011) peak to a lower 2θ angle in the XRD patterns showed that Mo was successfully diffused into vanadium dioxide films. The phase transition temperatures were decreased continuously from 57.4 to 32.7 °C by decreasing the sputtering power of vanadium. The thinner Mo-doped VO₂ thin films showed higher luminous transmittance and lower transition temperature. Our results were shown to be an innovative preparation method to fabricate thermochromic VO₂ films with a low phase transition temperature, balanced luminous transmittance and solar modulation ability by thermal oxidation of V–Mo cosputtered alloy films.     

Synthesis and properties of poly[2-(4′-oxyphenylene)-5-benzimidazole] and a proton-exchange membrane produced on its basis

A monomer of the A-B type, 3,4-diamino-4′-carboxydiphenyloxide, has been synthesized via a series of consecutive transformations of 5-chloro-2-nitroaniline. The homopolycondensation of the monomer in Eaton’s reagent at 140°C yields poly[2-(4′-oxyphenylene)-5-benzimidazole] soluble in organic solvents. A membrane containing 51% H₃PO₄ (2.9 acid molecules pert monomer unit) and possessing a proton conductivity of 0.025 S/cm at 160°C is produced by doping a polymer film with 60% H₃PO₄.     

Synthesis and mesomorphic behavior of poly[(2S, 3S)-(+)-2-chloro-3-methylpentyl 4′-(ω-vinyloxyalkyloxy)biphenyl-4-carboxylate]s with ethyl and propyl alkyl groups

Summary The synthesis and cationic polymerization of (2S, 3S)-(+)-2-chloro-3-methylpentyl 4-(2-vinyloxyethyloxy)biphenyl-4-carboxylate (15–2) and (2S, 3S)-(+)-2-chloro-3-methylpentyl 4-(3-vinyloxypropyloxy)biphenyl-4-carboxylate (15–3) are described. The mesomorphic behavior of the resulting polymers is discussed as a function of the molecular weight and spacer length. Based on the second and subsequent heating and cooling scans, poly(15–2)s exhibit an enantiotropic S_X (unidentified smectic) phase. Poly(15–2) with DP=4 is only crystalline. Poly(15–3)s show an enantiotropic cholesteric phase and an inverse monotropic S_X phase.     

One-pot Synthesis of N-[Pheny1-(2-hydroxy-napthalen-1-y1) -methy1]-acetamide Catalyzed by SnCl4 · 5 H2O

采用SnCl4·5H2O为催化剂催化2-萘酚、苯甲醛和乙酰胺的三组分一锅法类Ritter反应合成了1-乙酰胺基苯甲基-2-萘酚(AAN).考察了原料配比、催化剂用量、反应温度和反应时间等因素对AAN收率的影响,确定了适宜反应条件为:n(2-萘酚)∶n(苯甲醛)∶n(乙酰胺)=1∶1.4∶1,催化剂用量为反应物总质量的6％、85℃反应35 min,AAN的收率可达96.2％.该合成工艺路线简捷,催化剂价廉易得,催化活性高,使用方便,反应条件温和,收率可观.     

Targeted Synthesis of Complex Spiro[3H-indole-3,2′-pyrrolidin]-2(1H)-ones by Intramolecular Cyclization of Azomethine Ylides: Highly Potent MDM2–p53 Inhibitors

Mouse double minute 2 (MDM2) is a main and direct inhibitor of the crucial tumor suppressor p53. Reports from initial clinical trials showed that blocking this interaction with a small-molecule inhibitor can have great value in the treatment of cancer for patients with p53 wild-type tumors; however, it also revealed dose-limiting hematological toxicities and drug-induced resistance as main issues. To overcome the former, an inhibitor with superior potency and pharmacokinetic properties to ultimately achieve full efficacy with less-frequent dosing schedules is required. Toward this aim, we optimized our recently reported spiro-oxindole inhibitors by focusing on the crucial interaction with the amino acid side chain of His96_MDM2. The designed molecules required the targeted synthesis of structurally complex spiro[indole-3,2′-pyrrolo[2,3-c]pyrrole]-2,4′-diones for which we developed an unprecedented intramolecular azomethine ylide cycloaddition and investigated the results by computational methods. One of the new compounds showed superior cellular potency over previously reported BI-0252. This finding is a significant step toward an inhibitor suitable to potentially mitigate hematological on-target adverse effects.     

Hydrogen-Atom Transfer Oxidation with H2O2 Catalyzed by [FeII(1,2-bis(2,2′-bipyridyl-6-yl)ethane(H2O)2]2+: Likely Involvement of a (μ-Hydroxo)(μ-1,2-peroxo)diiron(III) Intermediate

The iron(II) triflate complex ( 1 ) of 1,2-bis(2,2′-bipyridyl-6-yl)ethane, with two bipyridine moieties connected by an ethane bridge, was prepared. Addition of aqueous 30 % H₂O₂ to an acetonitrile solution of 1 yielded 2 , a green compound with λ_max=710 nm. Moessbauer measurements on 2 showed a doublet with an isomer shift (δ) of 0.35 mm/s and a quadrupole splitting (ΔE_Q) of 0.86 mm/s, indicative of an antiferromagnetically coupled diferric complex. Resonance Raman spectra showed peaks at 883, 556 and 451 cm⁻¹ that downshifted to 832, 540 and 441 cm⁻¹ when 1 was treated with H₂¹⁸O₂. All the spectroscopic data support the initial formation of a (μ-hydroxo)(μ-1,2-peroxo)diiron(III) complex that oxidizes carbon-hydrogen bonds. At 0 °C 2 reacted with cyclohexene to yield allylic oxidation products but not epoxide. Weak benzylic C−H bonds of alkylarenes were also oxidized. A plot of the logarithms of the second order rate constants versus the bond dissociation energies of the cleaved C−H bond showed an excellent linear correlation. Along with the observation that oxidation of the probe substrate 2,2-dimethyl-1-phenylpropan-1-ol yielded the corresponding ketone but no benzaldehyde, and the kinetic isotope effect, k_H/k_D, of 2.8 found for the oxidation of xanthene, the results support the hypothesis for a metal-based H-atom abstraction mechanism. Complex 2 is a rare example of a (μ-hydroxo)(μ-1,2-peroxo)diiron(III) complex that can elicit the oxidation of carbon-hydrogen bonds.