Water stable! Radiochemists have recently discovered silicon chemistry as a tool for the introduction of 18F into biomolecules for positron emission tomography (PET) imaging. 18F‐labeled PET tracers must be stable towards defluorination under physiological conditions. Here, a theoretical model of organofluorosilane hydrolysis is developed that correlates with the experimentally determined hydrolytic half‐lives and allows estimation of the stability of newly designed compounds (see scheme).
Secondary, but second to none : The use of secondary alkyl halides in transition‐metal‐catalyzed cross‐coupling reactions (see scheme) has advanced significantly over the last five years. Selected examples of these transformations are examined, including mechanistic and stereochemical aspects.
Going separate ways : By using π‐allyl–palladium chemistry (path A) and PdII‐catalyzed Claisen chemistry (path B), a highly selective stereodivergent synthesis of separable amide rotamers was achieved (see scheme).
In control : A new catalytic vinylogous Mukaiyama aldol reaction provides products with high diastereo‐ and enantioselectivities (up to 99 % de and ee; see scheme). The relative and absolute stereochemistry of a representative product was rigorously assigned by NMR and CD spectroscopies (measured and calculated), X‐ray diffraction, and quantum‐chemical calculations.
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.
Nice and easy : A very simple synthesis for dibenzopentalenes, which starts from 1‐bromo‐2‐ethynylbenzenes, has been developed. It uses Ni0 complexes (see scheme), from which a relatively stable NiII complex as an important intermediate has been isolated. Dibenzopentalenes with various functional groups can be prepared by the procedure, and their electronic properties are consistent with theoretical calculations.
Network formation: Comicellization of polystyrene‐block‐polyethylene oxide (PS–PEO) with non‐ionic surfactants leads to the formation of networks and chains of spheres. The aqueous network solutions are responsive to dilution, undergoing morphological transformations to cylinders with Y junctions and both two‐ and three‐dimensional toroids (see figure).
Reversible and non‐bonding interaction between SWNTs and ODCB is observed from the analyses of visible near‐infrared absorption data and Raman spectroscopies (see spectra). The solvent effect on SWNTs effectively controls the electronic structure of SWNTs under homogeneous conditions.
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).
Dynamic duo : Magnetic resonance imaging (MRI) can visualize deep regions of living bodies, whereas fluorescence measurement offers excellent sensitivity. These methods thus offer signal enhancement potential for detecting enzyme activities. A dual‐mode off/on probe to detect caspase‐3 activity by fluorescence and 19F MRI is presented.
A general solution : In situ synchrotron X‐ray scattering in a high‐pressure pulsed injection reactor (see picture) shows that magnetite nucleation and growth are temporally separated. Gram‐scale crystalline, pure phase, superparamagnetic magnetite nanoparticles were synthesized without surfactants in supercritical water in less than one hour using a laboratory‐scale continuous‐flow reactor.
A complex rotation : The solution conformation of spermidine (SPD) was elucidated by using diastereospecifically deuterated and 13C‐labeled derivatives to diagnose the orientation of seven conformationally relevant bonds. NMR coupling constants were determined for a complex formed from spermidine and adenosine triphosphate (ATP; see figure).
