Silica scaffolding : By employing functionalized mesoporous SBA‐15 silica, novel fluorescent cruciform‐silica hybrid materials are generated which preserve the desirable solution properties of cruciforms in the solid state for potential use in sensory schemes.
Chiral phosphepine 1 catalyzes the transformation of an array of hydroxy‐2‐alkynoates into saturated oxygen heterocycles with good enantioselectivity. Phenols are also shown to participate in such phosphine‐catalyzed cyclizations, including an asymmetric variant. This method provides a new approach to the enantioselective synthesis of tetrahydrofurans, tetrahydropyrans, and dihydrobenzopyrans.
Size matters: Nanometer‐sized gaps in aggregates of silver nanoparticles are generated by covering the nanoparticle surface with a bilayer of cetyltrimethylammonium bromide. The nanometer‐ to micrometer‐sized wells are lithographically generated on polydimethylsiloxane surfaces. The wells filled with the modified nanoparticles (see picture) and the effect of the aggregate size on SERS enhancement are investigated.
First insights into the reaction between a Baylis–Hillman adduct and an allene moiety have been obtained from the novel domino heterocyclization/cross‐coupling reaction of α‐allenols and Baylis–Hillman acetates, which furnishes [(2,5‐dihydrofuran‐3‐yl)methyl]acrylate derivatives in moderate to good yields.
Metal clamping in operation! Deprotonation of [η6‐2‐(9‐triptycyl)indene]tricarbonylchromium induces a haptotropic shift of the organometallic fragment from the six‐membered to the five‐membered ring, as in a→b . In the anion, rotation of the molecular paddlewheel is blocked by the bulky tripod. X‐ray crystal structures provide pictures of the system in both its “ON” and “OFF” states.
On an atomic scale and with high sensitivity, solid‐state NMR spectroscopy can provide information about the electronic spin density and coupling mechanisms in paramagnetic compounds. The picture shows how the hyperfine splitting collapses through relaxation. Insights into which compounds are suitable and which approximations have to be made are given.
Functionalized nanodiamonds : Various functional groups have been incorporated into the structures of the naturally occurring diamondoids [1(2)3]tetramantane and [12312]hexamantane (cyclohexamantane), which represent hydrogen‐terminated prism‐shaped nanodiamonds (see picture). The attachment points define the use of these diamond‐like molecules as geometric building blocks for a variety of applications.
Target detection by the naked eye : The action of an RNA‐cleaving allosteric DNAzyme in response to ligand binding was coupled to a rolling circle amplification process to generate long single‐stranded DNA molecules for colorimetric sensing (see scheme). Upon hybridization of the resulting DNA with a complementary PNA sequence in the presence of a duplex‐binding dye, the color of the dye changed from blue to purple.
Chemical scrabble : Mechanistic studies of complex organocatalytic cascade reactions are challenging owing to the presence of many species involved. Electrospray ionization mass spectrometry provides details about a one‐pot quadruple organocatalytic cascade reaction, and allows detailed characterization of the reaction and its key intermediates.
On the big screen : A chiral biphenol catalyst screening protocol was developed for the rapid identification of enantioselective nucleophilic boronate reactions with acyl imines (see scheme). The approach successfully identified a unique catalyst for the reaction of aryl, vinyl, and alkynyl boronates. Mechanistic studies demonstrate boronate ligand exchange with the catalyst is necessary for activation towards nucleophilic addition.
A black whole : The black insoluble biopolymer eumelanin is prepared through the oxidative polymerization of 5,6‐dihydroxyindoles (see scheme). It has a largely unknown heterogeneous structure and unique optoelectronic properties. Current structural models are presented and possible applications are discussed.
Don't cry! The attachment of ferrocene moieties on the surface of carbon nano‐onions influences the electrochemical properties of these moieties and the photophysical properties of the carbon nano‐onions (see figure). Quantum chemical calculations confirm that the spectral properties of carbon nano‐onions depend on their size and the degree of functionalisation.
A process of elimination : Optical spectra of the Br2 product eliminated from the photodissociation of 1,1‐dibromoethylene at 248 nm are obtained (see picture), and the subsequent dissociation pathways are proposed with the aid of ab initio potential energy calculations. The behavior of the compound is compared with that of 1,2‐dibromoethylene.
Losing the grip : The synthesis of multivalent low‐molecular‐weight dendrons with lysine branching units coupled to disulfide‐linked spermine surface groups is described. It is furthermore demonstrated that the dendrons bind DNA with good affinity (see image), but are also able to release the DNA in a reductive environment.
Mimicking photosynthesis : The concept of light‐harvesting by using a mechanically interlocked [3]rotaxane is developed through synthesis and characterization. Our results provide a new candidate for light‐harvesting systems and also open up the possibility of creating intelligent or controllable energy‐collecting machines (see figure).
Highly activated thioesters formed by the rapid reaction of C‐terminal thioacids derived from protected amino acids and peptides with the Sanger reagent and other electron‐deficient aryl halides in the presence of a free amine immediately form a peptide bond with the amine. This essentially epimerization‐free method was used for the 4+4 block synthesis of a hindered octapeptide (see scheme; Boc, Pbf, and Trt are protecting groups).
Confined, but happy : The triflate salt of a germanium(II) dication, an atomic cation of a nonmetal, was isolated by encapsulation in [2.2.2]cryptand (see formula and molecular structure in the crystal). The cryptand satisfies the electron demand of the cation and sterically protects it (see space‐filling depiction, right).
