Building bridges : The title compound forms an unprecedented polymeric structure with bridging B–H–B three‐center two‐electron bonds in the solid state. This organoborane serves as an efficient precursor for the preparation of boron‐doped π‐conjugated polymers by hydroboration polymerization with a functionalized 1,4‐diethynylbenzene (see picture). These polymers form thin films that show intense green luminescence.
Switching characteristics: The 633 nm wavelength of an He–Ne laser is used to fabricate holographic transmission gratings in polymer‐dispersed liquid‐crystal cells. The microstructure and diffraction efficiency (η) both improve with increasing functionality (see figure). For functionalities of 2.5 or more, η approaches 34 % and can be switched off with electric fields of about 20 MV m?1.
DNA hybrid catalysis goes organometallic : A DNA strand functionalized with diene ligands forms iridium(I) complexes that can efficiently catalyze an allylic amination in aqueous medium (see scheme). The DNA‐based complexes show high stability and activity, and their secondary structure influences the stereoselectivity of the reaction.
Positive discrimination : Chemo‐ and regioselective palladium‐catalyzed cycloetherification of allendiols, namely β,γ‐ and γ,δ‐allendiols, may occur by judicious choice of palladium‐catalyzed conditions owing to their potential ability to discriminate between both nucleophilic sites (see scheme).
Cutting the corner : An excellent agreement has been obtained between experimental and computed coulombic coupling matrix elements for donor–spacer–acceptor systems, which consist of a boron dipyrromethane donor and acceptor in various stages of protonation. This correlation occurs in spite of reservations about the validity of Förster theory being applied to intramolecular electronic energy transfer (ET) over short (e.g., 20 Å) distances (see picture).
At first sight , carbon nanotubes seem to be perfect materials, but appearances can be deceptive. Carbon nanotubes contain impurities and these impurities are often contaminated by yet other impurities. Interestingly, while main impurities (such as Co and Mo) are not electrochemically active, impurities of impurities (such as Fe in this case) dominate the electrochemistry of carbon nanotubes for reduction of important biomarkers, such as hydrogen peroxide. H. Iwai and M. Pumera discuss the importance of this observation in their Full Paper on page 554 ff.
Dendrimers for ion sensing : The synthesis and use of new tris‐alkynyl dendrons are reported. So‐called “click” reactions of the dendrimers described with azidomethylferrocene give 27‐ferrocenyl, 81‐ferrocenyl, and 243‐ferrocenyl dendrimers. Electrochemical recognition of oxo‐anions and Pd2+ cations has been compared using the three polyferrocenyl dendrimers.
Guest Effect : The differences of nitrogen atom positions and the bridge bonds linked to two pyridine rings of some bipyridine guests can significantly affect the binding abilities and inclusion geometries of β‐cyclodextrin with the guests in both the solution and solid states.
Easy and direct : Regioselective Mizoroki–Heck‐coupling reactions using heteroaromatic tosylates as electrophiles were achieved, thus providing direct and easy access to highly functionalized α‐heteroarylvinyl amides and ethers.
Ask a copper : A copper(II) salt/chiral dipyridylphosphine/PhSiH3 system (see scheme) acts as a very effective and practical catalyst for the asymmetric reduction of heteroaromatic and other types of ketones in air with good‐to‐excellent enantioselectivities (up to 94 %), giving many chiral alcohols that are intermediates for physiologically active compounds. Remarkable temperature effects were observed for some heteroaromatic ketones.
Spinning wheels : The presented highly resolved multifrequency continuous wave EPR spectra (e.g., see figure) of the heterooctametalic “wheels” Cr7M provide rare examples of high nuclearity polymetallic systems where detailed information on the spin‐Hamiltonian parameters of the ground and excited spin states is observed.
The effect of carbon is subtle but sweet : The flexible C‐linkage in the newly synthesised C‐glycosyl mimetic, Manα(1,6)‐C‐ManαOPh allows OH? π bonding, both in the gas phase and in aqueous solution. This interaction is absent in the O‐linked disaccharide (see figure).
Changing places : Intramolecular B(pin)/H exchange took place in the presence of a platinum–phosphane catalyst, giving synthetically useful cis‐β‐methyl‐substituted alkenylboronates stereoselectively (see scheme; B(pin)=4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl).
