Breaking with convention: In the textbook aromatic annulenes the p orbitals are oriented perpendicular to the ring plane. In trannulenes the p orbitals form a cyclic, conjugated π system within the ring plane (see scheme). This concept of “in-plane” aromaticity was first recognized in 1979, and now representative compounds have been synthesized. The all-trans configuration of the annulene ring is stabilized by a fullerene framework, and the novel physicochemical properties of trannulenes open new opportunities for the design of light-harvesting compounds.

Decoding technology: Besides mainstream applications in transcription profiling, DNA microarrays are currently being explored as tools for the deconvolution of synthetic libraries. Current examples include the discovery of a new type of organic reaction and the screening of peptide nucleic acid encoded inhibitor libraries to investigate new proteolytic activities from dust mite extracts (see picture).

Wrapped around the finger! It has been known for a long time that histones organize the structure of cellular DNA. The news, however, is that histones are also able to influence elementary DNA-dependent processes. The type and number of specific histone modifications (examples rendered in gray) determine in advance if and when a gene is transcribed. The first modulators of histone-modifying enzymes have already become promising drugs.

A new level of programmability and freedom in directing the crystal growth of cuprous oxide was demonstrated by controlling the degree of branching and crystal habit in a systematic manner during electrodeposition. Examples of Cu₂O crystals in which these features were directed by rationally designing a growth condition and growth history are shown (scale bar=1 μm).

Cooperation of mother and daughter vesicles, which are self-assembled from an ill-defined hyperbranched copolymer, leads to fission of the daughter membrane in a cytomimetic process (see picture; red: mother vesicle, green: daughter vesicle). This is the first example of giant polymer vesicles (5–200 μm) being used as model membranes.

Crystallization of the thermodynamically metastable β glycine is explained on the basis of its growth at the opposite poles of the crystal (see graph) and by considering the structure of the relevant surfaces of the three polymorphs and their interactions with solvent molecules.

A twist in catalysis! The chirality of DNA is transferred directly to a Diels–Alder reaction by using a DNA-tethered catalyst. A catalytically active copper complex with achiral ligands self-assembles with DNA to give products with up to 90 % ee, as is the case for the exo isomer of product 1.

Cross-correlated relaxation (CCR) can be used to describe the structure and dynamics of biomolecules (see picture). By combining theoretical and experimental techniques in the study of proteins, for example, it is possible to acquire detailed information concerning the local anisotropic motion of the peptide plane from a single cross-correlation: the C′/NH CCR rate.

Don't forget to write! Electrochemical charge storage in a ruthenium-based monolayer on a hydrophilic substrate (for example, indium tin oxide coated glass) produces redox switching of the optical properties of the system (see picture). This read/write process can be carried out at low voltage in air and monitored by UV/Vis spectrophotometry. This makes the monolayer system a suitable candidate for nonvolatile memory devices.

Color sense: A reversible phase transition occurs with a change in color and structural properties on exposure to water vapor of the 1D halogen-bridged dinuclear platinum compound [NH₃(C₄H₈)NH₃]₂[Pt₂(pop)₄I]⋅4 H₂O (pop=P₂O₅H₂²⁻; see microscope images in reflection mode). This transition takes place between a paramagnetic charge-polarization state (296 K) and a diamagnetic charge-density-wave state (340 K).

The mesoporous silica superstructure SBA-1 was studied to obtain a formulation in terms of curvature that is important for surfactant structures and the mechanism of formation of inorganic replicas. The picture shows an oblique view of the atomistic model used to calculate the X-ray diffraction patterns. Green regions represent the inorganic hydroxylated silica wall of SBA-1, and the blue volume contains micellar surfactant surrounded by adsorbed water.

A complex situation: Two different types of neutral guest molecules are recognized through a combination of noncovalent interactions by a hydrogen-bonded receptor which displays two different modes of complexation: nonselective-exo and selective-endo complexation (see schematic representation). Furthermore, the hydrogen-bonded trimer can be selectively released.

Starting from α-bromovinylarenes, propargyl bromides, and dienophiles, a novel intermolecular tandem Pd-catalyzed cross-coupling/[4+4] and [4+2] cycloaddition sequence provides bicyclo[6.4.0]dodecane derivatives by a rapid synthesis in one reaction vessel. Five components are assembled into one molecule in this process. EWG=electron-withdrawing group.

Thermolysis of benzoylacetonate complexes proved successful in the synthesis of rare-earth oxide nanocrystals. CeO₂ nanopolyhedra, Eu₂O₃ nanodisks, and Pr₂O₃ nanoplates display 2D ordering on copper grids (see figure), and the former two show interesting optical properties arising from surface-modification effects.

Hydrogen bonding and π–π interactions are the driving forces for the self-assembly of a diamide organogelator into nanotubes in organic solution. Freeze-fracture electron microscopy (see image) and small angle neutron scattering studies show the tubes have a diameter of (24.2±0.3) nm with a wall thickness of (3.3±0.4) nm and an aspect ratio of 1:50 or higher.

A room-temperature diastereoselective [1,3] rearrangement results from treatment of 2,5-dihydrooxepins with EtAlCl₂ (see scheme). A modular synthesis of dihydrooxepins allows substituents to be incorporated at any position on the ring, which means that various polysubstituted cyclopentenes can be prepared through this Lewis acid mediated [1,3] ring contraction.

Ready cleavage of dioxygen and its selective insertion into Rh–alkene bonds occurs in the presence of [{Rh(PhN₃Ph)(C₈H₁₂)}_n] (n=1 and 2). The structure of the resulting dirhodadioxetane complex (see picture) and kinetic measurements support a dimetallic mechanism for this process that occurs with 100 % atom economy.

A stabilizing influence: Heterocyclic diaminophosphines can stabilize diphosphineimines sufficiently to allow the preparation of metal complexes. A kinetically stable diphosphineimine is isolated and its coordination chemistry investigated through the preparation of molybdenum (see picture) and nickel complexes with such PPN ligands.

Water, the medium of choice: Many reactions, such as Claisen rearrangements (see scheme), are dramatically accelerated when performed in aqueous suspension (“on water”) relative to organic solvents or even neat conditions. Low miscibility of organic compounds with water is not detrimental: in fact, it facilitates the isolation of products.

Like a sea squirt: An efficient biomimetic synthesis of the antitumor α-carboline marine alkaloids grossularine-1 (1) and N,N-didesmethylgrossularine-1 (2) is based on a novel oxidative dimerization of 2-amino-4-(3-indolyl)imidazole.

Mapping of bond connectivity in the carbon cage of the endohedral metallofullerene anion [La@C₈₂-A]⁻ (see picture, bottom) and definitive assignment of all the NMR signals were achieved for the first time by means of 2D INADEQUATE NMR spectroscopy measurements (see picture, top). The position of the encapsulated lanthanum atom (red sphere) was also confirmed by measurements of relaxation time T₁ for the cage carbon atoms.

Proposal accepted: NMR experiments have shown unequivocally that the previously only proposed zwitterionic carbon–carbon Meisenheimer–Wheland complexes are formed in the reaction of 4,6-dinitrobenzofuroxan (DNBF) with 1,3,5-tris(N,N-dialkylamino)benzenes. Increasing the temperature results in a rapid exchange between three homomeric forms of the complex (see scheme; NR₂=piperidyl, morpholinyl, pyrrolidinyl).

Monitoring the cleavage of phosphiranes 1 and 2 by using a variety of low-temperature and time-resolved spectroscopic techniques has shown that triplet mesitylphosphinidene (3) is the principal product of this photolytic reaction (see scheme). Results obtained by using laser flash photolysis show that 3 is readily quenched by reactive π systems.

Enolate–homoenolate equivalents 1 can be prepared in one step by the title reaction. They act as functionalized Z-γ-siloxyallyl zinc reagents 2 by undergoing ring opening in the presence of a Lewis acid. Addition of 2 to tosylimines gives vic-amino alcohols with high diastereoselectivity, presumably due to a fixed conformation resulting from coordination of the metal atom.

Disguise tactics: Peptide–polymer hybrid nanotubes are constructed in which self-assembled cyclic peptides govern the structure, and a synthetic polymer coating determines the surface chemistry. Formation of the latter is initiated in situ from preorganized peptide building blocks. The picture shows an AFM image of nanotubes on a silicon wafer.

The magnetic interactions between the unpaired electron and the nitrogen donors of the porphyrin ring in the copper(II) complex of N-confused tetraphenylporphyrin, [Cu^II(nctpp)], were studied by continuous-wave (cw) and pulse EPR methods (see picture). A pronounced asymmetric distribution of the spin density on the three core nitrogen nuclei was found, in contrast to the spin density distribution in the symmetric [Cu^II(tpp)] complex.

Neither the olefin geometry nor the configuration of secondary allylic substrates in palladium-catalyzed allylic alkylations of chelated enolates has an influence on the newly formed stereogenic center of the amino acid (see scheme, TBDPS=tert-butyldiphenylsilyl, Tfa=trifluoroacetyl). This is controlled exclusively by the protecting group on the chiral center. Therefore, the choice of the protecting group on the allylic alcohol can lead to either of the diastereomeric amino acids in a highly stereoselective fashion.

Wait a moment: The strong ligand field within the M₃N cluster of the endohedral cluster fullerenes Ho₃N@C₈₀ and Tb₃N@C₈₀ accounts for the unusual net magnetic moment of the compounds. As a result of these interactions the individual magnetic moments m of the metal ions (M = Ho or Tb) are not parallel or antiparallel to each other, but parallel to the MN bond (see scheme).

Full of air: Electrostatic layer-by-layer assembly of polyelectrolyte multilayers was successfully accomplished on the surface of an air microbubble (core). The resulting polyelectrolyte shell stabilizes the air microbubbles against collapse and prevents the dissolution of air in aqueous media. Air-containing polyallylamine/poly(styrene sulfonate)(PAH/PSS) microcapsules have a broad size distribution (1–20 μm).