Angewandte Chemie International Edition

The red smear cheeses shown on the cover obtain their color from bacteria such as Brevibacterium linens, which contain highly effective antioxidant and photoprotective phenolic carotenoids such as 3,3′-dihydroxyisorenieratene (DHIR). In their Communication on page 400 ff., H.-D. Martin, W. Stahl, and co-workers describe the synthesis of DHIR and their investigation of its antioxidative and photoprotective properties. Its quinoid oxidation product is blue in color.

Superstable foams that contain air bubbles stabilized by modified, rigid CaCO₃ rods are reported by W. Liu, S. Stoyanov, and co-workers in their Communication on page 378 ff. The very high stability and stiffness of the rod-stabilized bubbles means that their spherical shape is retained when dried on glass substrates. Despite the massive difference in length, the surface pattern of a 120 micrometer bubble with 25 micrometer rods is similar to that of 10 meter logs on a river surface.

Four thought: The first nickel(IV) complex that contains only alkyl ligands (see picture) was serendipitously obtained in a reaction between a nickel(0) species and a strained diolefin. The twisted conformation of the ligand provides the necessary steric shielding to stabilize the complex. DFT calculations show this conformation to be the ground state and NMR spectra indicate the diamagnetic nature and high oxidation state of the nickel center.

Redox paradox? The initial one-electron oxidation of a metal ion induces a multi-electron rearrangement, leading to oxidation of the second metal ion and reduction of the tetraoxolate dianionic ligand bridging the two metals (see scheme). These electron-transfer events were observed with numerous spectroscopic, electrochemical, and crystallographic methods (TpyA=tris(2-pyridylmethylamine).

How to deliver a drug: The current state of knowledge of drug carriers based on soft matter is presented, and in particular, the advantages and drawbacks of matrix and vesicular systems are discussed. An overview is given of their preparation, transposition to the industrial scale, and possible applications in vectorization.

Ni takes a load off: Nickel(0) and a strained alkene react to form a stable tris(alkene) complex, which eliminates the corresponding trans,trans,trans-cyclobutane upon heating. A higher proportion of alkene to Ni⁰ precursor yielded the first all-alkyl complex of nickel(IV) (see structure; Ni: green). These reactions, which involve ligand coupling, are driven by relief of ring strain in the alkene.

Positively phosphorus: A solvent-free melt system (P₄/Ph₂PCl/GaCl₃) represents a powerful medium for the functionalization of the P₄ tetrahedron to form new cationic phosphorus-rich organophosphorus cage and cluster systems, such as [Ph₂P₅]⁺, [Ph₄P₆]²⁺, and [Ph₆P₇]³⁺ (see picture), by insertion of [Ph₂P]⁺ into PP bonds.

Accurate and tunable: The title compounds can detect reactive oxygen species (ROS) in cell culture, tissue explants, and for the first time in vivo. The hydrocyanines are synthesized by reduction of the cyanine dyes with NaBH₄. They can accurately detect nanomolar levels of ROS, have excellent stability against autoxidation, and have tunable emission wavelengths in the range 560–830 nm.

Sensor and sensibility: A sensor that combines the properties of a europium complex and an organic-dye-doped silica nanoparticle allows the rapid and ultrasensitive detection of an anthrax biomarker (see picture yellow dots: silica nanoparticles, outer shell: Eu^III complex). The sensor response is superior to that obtained with traditional terbium-based sensors.

On the blue Nile: NAD(P)H-sensitive Nile Blue functionalized CdSe/ZnS quantum dots have been developed for the optical sensing of biocatalytic processes involving NAD⁺-dependent enzymes and the screening of anticancer drugs by monitoring intracellular metabolism (see picture).

Intrinsically chiral: The compounds (C₄H₁₂N)₂ [M₂Al₁₀P₁₂O₄₈] (denoted MAPO-CJ40; M=Co, Zn) were solvothermally synthesized. Their structure contains one-dimensional helical 10-ring channels enclosed by double-helical ribbons of the same handedness made of the edge-sharing of 6-rings along the 2₁ screw axis. The framework is intrinsically chiral and exhibits a new zeotype structure.

Clustering together: A shuttle-based fluorogenic cluster transfer, in which silver clusters (SCs) are directly transferred from a low-molecular-weight poly(acrylic acid) (PA) shuttle to a single-stranded DNA (ssDNA) tag on the protein of interest (see picture), proceeds with excellent specificity. Upon transfer, the cluster fluorescence increases more than ten times, which provides bright, photostable labeling.

MRI jack-o'-lanterns? Hollow manganese oxide nanoparticles (HMON) show greatly improved relaxivities and drug-loading capacities compared to those with solid interiors (WMON). Their efficient cellular uptake demonstrates their potential as a bifunctional medical system that combines diagnostic imaging and targeted therapy.

Off-the-shelf, prêt-à-porter multianalyte sensing systems are based on the ability of cell-penetrating peptides (CPPs; see picture, blue) to mediate the export of hydrophilic anions (yellow→green) from lipid bilayer vesicles (gray). Covalent capture of hydrophobic analytes (black) with hydrophilic anions (red) produces amphiphilic anions that can activate CPPs.

Thinking in compartments is back! The degradation of a fluorescently labeled nucleic acid substrate within a polymer capsule by coencapsulated DNase I was initiated by activation of the enzyme with a chemical trigger. The degraded DNA diffused from the capsule (see picture). The semipermeable capsule microreactors enable external reaction control, high-throughput tracking of reaction progression, and continuous modification of the DNA cargo.

Worth diene for: The butadienylphosphine L (see scheme), obtained on a large scale from a new synthetic method, is an efficient ligand in Ullmann-type copper-catalyzed arylation reactions. The use of this phosphorus ligand made it possible to follow the reaction by ³¹P NMR spectroscopy and thus to propose a mechanism for the Ullmann reaction.

Phasing up to matters: The use of aqueous ammonia in a biphasic system with a copper catalyst and diketone supporting ligands allows the catalytic amination of both activated and unactivated aryl and heteroaryl iodides and bromides under very mild conditions (see scheme; R=electron-donating or -withdrawing group; acac=acetylacetonate).

Controlling the regioselectivity: The phenylsulfonyl group controlled the regioselectivity in the title reaction to afford pyrrolidine-2,3-dicarboxylates with good regioselectivity and high exo selectivity and enantioselectivity (see scheme). The products are precursors to substituted pyrrolidines and pyrrolines that are not attainable by direct 1,3-dipolar cycloadditions with typical acrylates.

Click by click: Dual labeling of model compounds was carried out by using copper-free and copper-mediated click chemistry in a sequential manner. This method was used to introduce two labels onto biological targets or nanoparticles, thus quickly converting them into fluorescence resonance energy transfer systems.

Cop some rings: A simple and highly efficient copper-catalyzed method for the synthesis of quinazolinone derivatives through the reaction of substituted 2-halobenzoic acids with amidines or guanidines under mild conditions has been developed (see scheme). The method has economical and practical advantages.

Increasing the mass makes a mess: Partial or total deuteration of the protonated water dimer drastically alters its vibrations. Coupling between certain vibrational modes is strongly enhanced, whereas other modes are decoupled. Full-dimensional quantum-dynamics simulation and assignment of the IR spectrum of various isotopologues of the cation show the intricate dynamics of the smallest protonated water cluster.

Nature inspired: A synthetic receptor (see picture) that exploits two zinc(II) ions and four convergent amino hydrogen bonding groups binds lipopolysaccharides (LPSs) almost as strongly as the LPS binding protein. This feature is exploited to electrochemically distinguish LPS from other pathogens in water and in complex biological mixtures. Zn pink, N blue, P orange, O red.

Sowing the seeds: Binary colloidal particles of controlled morphology, including line segments, triangles, tetrahedra, octahedra, and square antiprisms (see picture) were obtained by an emulsion polymerization of styrene in the presence of silica seeds. These morphologies result from the minimization of an energy term that is the sum of two forces—an attraction towards the center and two-body particle repulsions that balance the attractive force.

Marrying nobility: Quantum chemical calculations predict that the dixenon compound HXeXeF has an activation barrier for decomposition of about 11 kcal mol⁻¹, which should be large enough to identify the molecule in a low-temperature matrix.

It all adds up: The dienophilic reactivity of 2-methyl-substituted quinones has been substantially increased by the introduction of a boronic acid substituent, which makes them equivalent to a highly reactive quinone. The Diels–Alder reactions of these quinones are followed by spontaneous and stereoselective protodeboronation to give the trans-fused adducts. The boron group is a temporal regiocontroller and leads to the uncommon meta adduct.

Changing the channel: Dodecanal and pyrogallol were condensed to give a tetramer, which was crystallized as the bilayer and the hexameric molecular capsule. A copper-seamed metallogallarene capsule functioned as an ion transporter and showed selectivity for potassium over chloride ion transport in a phospholipid bilayer (see picture). The capsule also showed voltage-dependent gating of its open–close behavior when examined in asolectin membranes.

I'm forever blowing bubbles: Superstable foams comprising air bubbles stabilized by modified, rigid CaCO₃ rods have a bimodal bubble-size distribution. The very high stability and stiffness of the rod-stabilized bubbles means that their spherical shape is retained when dried on glass substrates and that they could be ordered into 2D binary colloidal crystals, with large bubbles at the bottom and small bubbles filling the spaces in between (see picture).

Unusually sensitive: A chiral sensor based on 1,1′-bi-2-naphthol was prepared, which can provide visual enantioselective discrimination of α-hydroxycarboxylic acids. When the sensor and the acid have matched configurations, an enantioselective precipitation occurs, which is accompanied by a dramatic (over 950-fold) solid-state fluorescence enhancement (see picture).

Let's start at the very beginning: Reaction simulations were used to clarify differences between autoinductive and autocatalytic processes in the context of recent models pertaining to the chemical origin of life (see plot). The ability of a catalytic network to persist in the face of disruptive challenges is essential to its potential to play a role in prebiotic chemistry.

A little cooperation: A cooperative copper- and palladium-catalyzed highly regio- and chemoselective three-component coupling of benzynes, allylic epoxides, and terminal alkynes provides an efficient atom-economical route to ortho-disubstituted arenes. The resulting product undergoes a gold-catalyzed cyclization reaction (see scheme; dba=dibenzylideneacetone, dppp=1,3-bis(diphenylphosphanyl)propane).

A Platonic relationship: Calcite single and mesocrystals with two platonic shapes and minimal surfaces are formed by a unified polymer-controlled nanoparticle aggregation. The shapes of the crystals (see picture for example) are tuned by the reactant concentration. The morphogenesis follows a nonclassical mechanism. A rhombohedral primitive minimal surface was observed for the first time in a synthetic crystallization of micrometer-sized particles.

The color of red smear cheeses arises from naturally occurring carotenoids like 3,3′-dihydroxyisorenieratene (1). This compound and its oxidation product 2, which have unusual phenolic and quinoid end groups, respectively, were synthesized. The antioxidant and photoprotective properties of a series of carotenoids were tested with eight different model systems, and 1 proved to be superior to other carotenoids.

Compass component: Blue-light excitation of the photoreceptor cryptochrome generates a transient radical pair by electron transfer from a tryptophan (Trp) at the surface to the flavin cofactor in the center of the protein (see picture; FAD=flavin adenine dinucleotide). Simulated EPR spectra show that the electronic coupling parameters of these radical pairs are suitable for animal magnetoreception.