Two‐Dimensional Core‐Shelled Porous Hybrids as Highly Efficient Catalysts for the Oxygen Reduction Reaction

Two‐dimensional (2D) transition‐metal dichalcogenides (TMDs) have drawn much attention due to their unique physical and chemical properties. Using TMDs as templates for the generation of 2D sandwich‐like materials with remarkable properties still remains a great challenge due to their poor solvent processability. Herein, MoS₂‐coupled sandwich‐like conjugated microporous polymers (M‐CMPs) with high specific surface area were successfully developed by using functionalized MoS₂ nanosheets as template. As‐prepared M‐CMPs were further used as precursors for preparation of MoS₂‐embedded nitrogen‐doped porous carbon nanosheets, which were revealed as novel electrocatalysts for oxygen reduction reaction with mainly four‐electron transfer mechanism and ultralow half‐wave potential in comparison with commercial Pt/C catalyst. Our strategy to core–shelled sandwich‐like hybrids paves a way for a new class of 2D hybrids for energy conversion and storage.     

Stickstoffmonoxid,Superoxid und Peroxynitrit: Radikalchemie im Organismus

^˙NO is an arginine‐derived signal molecule which together with prostacyclin is involved in blood vessel relaxation. Superoxide (^˙O2‐) being a radical like ^˙NO, almost quantitatively traps ^˙NO under formation of peroxynitrite, which is able to oxidatively modify biomolecules. Already submicromolar concentrations of peroxynitrite selectively cause a tyrosine nitration and inactivation of prostacyclin synthase. The mechanism of this nitration could be explained by a heme‐thiolate‐catalyzed homolytic cleavage of peroxynitrite followed by the formation of a ferryl/^˙NO2 intermediate. By this nitration reaction the superoxide radical gains a new function as a signal molecule with antagonistic actions to ^˙NO. Inflammatory conditions upregulate ^˙NO and superoxide in many cells and by the generating higher levels of peroxynitrite cause pathophysiological effects. Such oxidative changes may be a future target for pharmacological interventions by suitable antioxidants.     

Spectroscopy of conjugated polymers: phosphorescence and delayed fluorescence

We report on the observation of delayed fluorescence (DF) and phosphorescence (P) from films and dilute frozen solutions of various conjugated polymers of the PPP‐type. The materials differ with respect to the rotational freedom along the polymer backbone. Upon pulsed optical excitation into the S₁←S₀ transition of the materials, delayed emission occurs on a time scale of μs to ms in solid films at 80 K. The phosphorescence in dilute frozen solution decays monoexponentially with a radiative lifetime on the order of one second. The data analysis reveals that the DF is caused by recombination of geminate electron hole pairs rather than triplet‐triplet annihilation. This conclusion is supported by investigations of the response of the DF to an applied electric field.     

Dialkylcyclopentadithiophene Polymers and Copolymers

Poly(2,6‐(4,4‐dialkyl)‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene) (PCPDT) homopolymers and poly[(2,7‐(9,9‐dialkyl)fluorene)‐co‐(2,6‐(4,4‐dialkyl)‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene)] (PF/PCPDT) copolymers have been synthesized according to Yamamoto with Ni(COD)₂ (or NiCl₂/Zn in the case of the homopolymer). PCPDT is characterized by a red‐shifted long wavelength absorption maximum (565 nm) when compared to that of polyfluorene (PF, 378 nm). In contrast to PF, its heteroaromatic analogue PCPDT does not form thermotropic LC phases. The PF/PCPDT copolymers show clear indications for a block copolymer character (two separated π‐π* absorption maxima, two glass transitions).     

X‐ray Rotation‐Tilt‐Method — First Results of a new X‐ray Diffraction Technique

That from us as X‐ray Rotation‐Tilt Technique (XRT Method) designated procedure principle represents a world innovation and overcomes essential disadvantages of comparable diffraction techniques known up to now. Starting from the origin and the informational content of the XRT interferences a realization of a special equipment and selected examples of some first applications are presented.     

Liquid crystalline polyfluorenes for blue polarized electroluminescence

A series of 9,9‐dialkyl‐poly(fluorene‐2,7‐diyl)s containing linear and branched alkyl substituents with a M_n of up to 200000 g/mol has been synthesized. Moreover, some of the polymers were end capped with a suitable hole transport functionality, such as a triphenylamine derivative, to improve their charge transport properties and to control the molecular weight. The thermal alignment of these novel polymers on a rubbed polyimide layer led to highly anisotropic film formation with dichroic ratios (absorption parallel and perpendicular to the rubbing direction) of up to 26 in absorption and 21 in emission.     

Nanomolar Inhibitors for Two Distinct Biological Target Families from a Single Synthetic Sequence: A Next Step in Combinatorial Library Design?

One common synthetic route creates small-molecule libraries directed toward two functionally distinct target families. The novel structural template 1 can independently display the necessary pharmacophore patterns for inhibition of members of two different biomolecular target families, the matrix metalloproteinases (MMPs) or the phosphodiesterases (PDEs). The incorporation of multiple target family directed design elements into combinatorial library design could help expedite the pharmaceutical lead discovery process. Z=OR′ (PDE4), H (MMPs).