Revelation of interfacial energetics in organic multiheterojunctions

Efficient charge generation via exciton dissociation in organic bulk heterojunctions necessitates donor–acceptor interfaces, e.g., between a conjugated polymer and a fullerene derivative. Furthermore, aggregation and corresponding structural order of polymer and fullerene domains result in energetic relaxations of molecular energy levels toward smaller energy gaps as compared to the situation for amorphous phases existing in homogeneously intermixed polymer:fullerene blends. Here it is shown that these molecular energy level shifts are reflected in interfacial charge transfer (CT) transitions and depending on the existence of disordered or ordered interfacial domains. It can be done so by systematically controlling the order at the donor–acceptor interface via ternary blending of semicrystalline and amorphous model polymers with a fullerene acceptor. These variations in interfacial domain order are probed with luminescence spectroscopy, yielding various transition energies due to activation of different recombination channels at the interface. Finally, it is shown that via this analysis the energy landscape at the organic heterojunction interface can be obtained

Synthesis of a new diarylhydrazone derivative and an evaluation of its in vitro biofilm inhibition and quorum sensing disruption along with a molecular docking study

International audienceMolecules that target quorum sensing and biofilm inhibition are useful antimicrobials. In this regard, a new diarylhydrazone was synthesized and characterized using infrared, high-resolution mass spectrometry and nuclear magnetic resonance experiments as N-[(E)-4-bromo-2,5-diheptyloxybenzylideneamino]-2,4-dinitroaniline (BHBANA). Minimal inhibitory concentrations (MICs) vary from 0.625 to 2.5 mg mL(-1). This compound was screened in vitro for its inhibition of quorum sensing-mediated violacein production by Chromobacterium violaceum CV12472 at MIC and sub-MIC and showed percentage inhibition varying from 100% at MIC to 5.7% and PLUSMN; 0.2% at MIC/32. Against Chromobacterium violaceum CV026, BHBANA exhibited anti-quorum-sensing zone diameters of 10.5 and PLUSMN; 0.3 mm and 7.0 and PLUSMN; 0.1 mm at MIC and MIC/2, respectively. BHBANA shows concentration-dependent inhibition of swarming motility on flagellated Pseudomonas aeruginosa PA01 with the highest % inhibition of 28.30% and PLUSMN; 0.50% and mu;g mL(-1) at MIC. The product inhibits biofilm formation, with the best biofilm inhibition being observed against Staphylococcus aureus varying from 72.24% and PLUSMN; 0.86% (MIC) to 09.82% and PLUSMN; 0.10% (MIC/8). Molecular docking studies carried out utilizing the Schrodinger software identified interactions between BHBANA and different receptor compartments of Chromobacterium violaceum, which can block pathogenic gene expression. The results suggest the potential of BHBANA in reducing microbial virulence

Anthracene-Containing Conjugated Polymer Showing Four Optical Transitions Upon Doping: A Spectroscopic Study

An anthracene-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene) (PAE-PAV) of general constitutional unit (PhCCAnthrCCPhCHCHAnthrCHCH)(n) bearing two 2-ethylhexyloxy solubilizing side chains on each phenylene (Ph) unit has been synthesized and characterized. The basic electrochemical characterization was done, showing the existence of two non-reversible oxidation and one reversible reduction peaks. The optical properties, the real and imaginary part of the dielectric function, were probed using spectroscopic ellipsometry (SE). The vibrational structure of the undoped/doped polymer was investigated using Fourier transformed infrared spectroscopy. A strong change in the polaronic absorption was observed during the doping, which after modeling revealed the existence of two separated transitions. The optical changes upon doping were additionally recorded using the SE technique. Similar to the results from FT-IR spectroscopy, two new in-the-gap absorptions were found. Moreover, the electrical conductivity as well as the mobility of positive carriers were measured. In the undoped state, the conductivity of the polymer was found to be below the detection limit (<S cm(-1)), after doping the conductivity increased to 0.69 S cm(-1). (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 338-34

Rhodium-Coordinated Poly(arylene-ethynylene)-<i>alt</i>-Poly(arylene-vinylene) Copolymer Acting as Photocatalyst for Visible-Light-Powered NAD⁺/NADH Reduction

A 2,2′-bipyridyl-containing poly­(arylene-ethynylene)-<i>alt</i>-poly­(arylene-vinylene) polymer, acting as a light-harvesting ligand system, was synthesized and coupled to an organometallic rhodium complex designed for photocatalytic NAD⁺/NADH reduction. The material, which absorbs over a wide spectral range, was characterized by using various analytical techniques, confirming its chemical structure and properties. The dielectric function of the material was determined from spectroscopic ellipsometry measurements. Photocatalytic reduction of nucleotide redox cofactors under visible light irradiation (390–650 nm) was performed and is discussed in detail. The new metal-containing polymer can be used to cover large surface areas (e.g. glass beads) and, due to this immobilization step, can be easily separated from the reaction solution after photolysis. Because of its high stability, the polymer-based catalyst system can be repeatedly used under different reaction conditions for (photo)­chemical reduction of NAD⁺. With this concept, enzymatic, photo-biocatalytic systems for solar energy conversion can be facilitated, and the precious metal catalyst can be recycled

Synthesis and Photophysical and Electroluminescent Properties of Poly(1,4-phenylene–ethynylene)-<i>alt</i>-poly(1,4-phenylene–vinylene)s with Various Dissymmetric Substitution of Alkoxy Side Chains

The synthesis and characterization of a set of conjugated polymers, poly­(1,4-phenylene–ethynylene)-<i>alt</i>-poly­(1,4-phenylene–vinylene)­s (PPE–PPVs), with a dissymmetrical configuration (partial or total) of alkoxy side chains is reported. Five new polymers bearing octyloxy and/or octadecyloxy side chains at the phenylene–ethynylene and phenylene–vinylene segments, respectively, were obtained. Two symmetrical substituted polymers were used for comparison. Polymers with weight-average molecular weight, <i>M</i>_w, up to 430 000 g/mol and degree of polymerization between 17 and 322 were obtained by a Horner–Wadsworth–Emmons olefination polycondensation reaction of the respective luminophoric dialdehydes and bisphosphonates. As expected, identical conjugated backbones in all polymers results in very similar photophysical response in dilute solution, with high fluorescence quantum yields between 50% and 80%. In contrast, the thin film properties are dependent on the combinatorial effects of side chain configuration, molecular weight, and film thickness parameters, which are the basis of the resulting comparison and discussion