Cover Picture: Toroidal Micelles of Uniform Size from Diblock Copolymers (Angew. Chem. Int. Ed. 25/2009)

Pure toroidal micelles of highly uniform shape and size are presented by T. Chang et al. in their Communication on page 4594 ff. The donut‐shaped micelles are prepared by spontaneous self‐assembly of a polyisoprene‐block‐poly(2‐vinylpyridine) copolymer, and are stable enough to act as a template for the growth of gold nanoparticles along the ring surface.

     

Exciton Binding Energies in Conjugated Polyelectrolyte Films

Molecular design: The electronic structure of conjugated polyelectrolytes as a function of ionization potential (IP) and electron affinity (EA) is determined using X‐ray absorption and emission spectroscopy (see figure). Different functional groups give rise to dissimilar transport gaps and exciton binding energies.

     

Convergence theorems based on hybrid methods for generalized equilibrium problems and fixed point problems

The purpose of this work is to introduce a hybrid projection method for finding a common element of the set of a generalized equilibrium problem, the set of solutions to a variational inequality and the set of fixed points of a strict pseudo-contraction in a real Hilbert space.     

A characterization of isometries on an open convex set,II

Let E ⁿ be an n-dimensional Euclidean space with n ≥ 2. In this paper, we generalize a classical theorem of Beckman and Quarles by proving that if a mapping, from an open convex subset Co of E ⁿ into E ⁿ , preserves a distance ρ, then the restriction of f to an open convex subset C _∞ of C ₀ is an isometry. This work was supported by 2007 Hongik University Research Fund.     

Tandem cyclization of alkynes via rhodium alkynyl and alkenylidene catalysis

A rhodium(I)-catalyzed tandem cyclization of alkynes has been developed. The reaction allows for multiple bond formations to occur at both the alpha- and beta-positions of alkynes under mild conditions to yield a variety of fused ring systems as the products. In the presence of triethylamine and the complex derived from [Rh(COD)Cl]2 and P(4-F-C6H4)3, a terminal alkyne is converted to a rhodium alkynyl species which reacts with a tethered alkyl halide at the beta-position to provide a beta,beta-disubstituted alkenylidene complex. The rhodium alkenylidene species then undergoes additional ring closures with a range of pendent functional groups such as alkene, hydroxyl, and phenyl groups through [2 + 2] cycloaddition, nucleophilic addition, and 6pi-electrocyclization processes, respectively.     

Catalytic one-pot synthesis of cyclic amidines by virtue of tandem reactions involving intramolecular hydroamination under mild conditions

A new synthetic methodology for the generation of cyclic amidines has been developed by the reaction of 1,n-aminoalkynes with electron-deficient azides using a ruthenium catalyst at ambient temperature. The reaction proceeds most likely via a tandem sequence of intramolecular hydroamination of aminoalkynes, cycloaddition of azides with the resulting enamines, and rearrangement of triazoline intermediates. It demonstrates, as the proof-of-principle, that an equilibria cascade sequence can be favorably driven by an irreversible step, thus enabling a facile one-pot synthetic route to deliver molecular complexity under unprecedented mild conditions without relying on the traditional linear approaches.     

A new photostable terrylene diimide dye for applications in single molecule studies and membrane labeling

A new terrylene diimide-based dye (WS-TDI) that is soluble in water has been synthesized, and its photophysical properties are characterized. WS-TDI forms nonfluorescing H-aggregates in water that show absorption bands being blue-shifted with respect to those of the fluorescing monomeric form. The ratio of monomeric WS-TDI to aggregated WS-TDI was determined to be 1 in 14 400 from fluorescence correlation spectroscopy (FCS) measurements, suggesting the presence of a large amount of soluble, nonfluorescent aggregates in water. The presence of a surfactant such as Pluronic P123 or CTAB leads to the disruption of the aggregates due to the formation of monomers in micelles. This is accompanied by a strong increase in fluorescence. A single molecule study of WS-TDI in polymeric films of PVA and PMMA reveals excellent photostability with respect to photobleaching, far above the photostability of other common water-soluble dyes, such as oxazine-1, sulforhodamine-B, and a water-soluble perylenediimide derivative. Furthermore, labeling of a single protein such as avidin is demonstrated by FCS and single molecule photostability measurements. The high tendency of WS-TDI to form nonfluorescent aggregates in water in connection with its high affinity to lipophilic environments is used for the fluorescence labeling of lipid membranes and membrane containing compartments such as artificial liposomes or endosomes in living HeLa cells. The superior fluorescence imaging quality of WS-TDI in such applications is demonstrated in comparison to other well-known membrane staining dyes such as Alexa647 conjugated with dextran and FM 4-64 lipophilic styryl dye.     

Conducting block copolymer for simple micro- to nanopatterns

To use conducting polymers as substitutes for metals and conventional semiconductors in device fabrication, a cost-effective process for the reproducible deposition of the conducting polymers is needed. In this letter, we report a simple solution casting method for the fabrication of micro- to nanopatterns using the conducting block copolymer, poly(thiophene-block-ethyleneoxide), which shows rectifying characteristics dependent on the pattern width.