Volume 7 Issue 9, September 2015

Electron transfer is ubiquitous across both life and modern technologies, and thus being able to control it is an attractive goal. Now, targeted infrared excitation has been used to modulate the efficiency of electron transfer in a series of donor–bridge–acceptor molecules.

Solid-state perovskite solar cells have recently emerged and have already reached efficiencies of 20%. Now, a simple solution-processing step that crosslinks neighbouring perovskite grain surfaces has been found to increase their stability, an important issue for future potential commercialization.

Controlling the site-selectivity of C–H activation reactions is a major obstacle for the development of synthetically useful methodology. Now, meta-C–H functionalizations of arenes have been achieved by exploiting weak secondary interactions of a metal-coordinating ligand with the substrate.

Preparation and structural characterization of the catalytic intermediates of two similar thiolate-ligated haem proteins (cytochrome P450 Compound-I and chloroperoxidase Compound-I) has explained the structural basis for the difference in their reactivity.

The ultrafast and mode-specific infrared excitation of several donor–bridge–acceptor (DBA) assemblies in solution has been shown to modulate their light-induced electron transfer properties. New insights are afforded into the role of vibrational processes immediately following light absorption in charge-transfer molecules and a recipe for efficient ‘vibrational control’ of electron transfer is proposed.

Cytochrome P450 (P450) and chloroperoxidase (CPO) are both thiolate-ligated haem proteins that form a ferryl radical species called compound I. P450-I is, however, significantly more reactive than CPO-I. Variable-temperature Mössbauer and X-ray absorption measurements have now shown that increased electron donation from the axial thiolate ligand in P450-I may explain its greater propensity for C–H bond activation.

Perovskite materials show great promise for solar cell devices, owing in particular to their high power conversion efficiency. Now, the addition of butylphosphonic acid 4-ammonium cations during a one-step process has been shown to improve both the efficiency and moisture stability of perovskite photovoltaics, through the formation of hydrogen-bonding crosslinks between neighbouring grains.

Directing groups in a substrate are frequently used to direct the regioselectivity of C–H activation reactions. Now it has been shown that regioselectivity can be directed by a ligand, which binds to both the catalysing metal centre and a distal hydrogen-bond acceptor in the substrate. This secondary interaction places the metal in close proximity to the reacting C–H bond.

Ring-opening metathesis polymerization (ROMP) offers good control over dispersity, but the requirement of one initiator per chain can be expensive and problematic for purification. Now, a reversible cyclohexenyl-containing chain-transfer agent is described, thus allowing a catalytic living ROMP process to produce narrow dispersity polymers and block copolymers.

Forged by evolution, the natural enzymatic pathways to aldose carbohydrates are complex. Now, a biocatalytic stereoselective one-pot assembly of these carbohydrates from formaldehyde and glycolaldehyde using engineered D-fructose-6-phosphate aldolase (FSA) variants has been developed that circumvents this complexity.

Graphene possesses numerous interesting properties yet the preparation of pristine sheets has remained challenging, hindering practical applications. Now, a rapid, highly efficient step has been devised that uses microwave irradiation in oligomeric ionic liquids to exfoliate graphite into pristine ‘single layer’ sheets (<1 nm thick). A concentrated dispersion of the resulting material behaves as a physical gel.

The complexity and diversity of natural product structures make them an ideal starting point for the creation of chemical libraries. Now it is shown that a semi-synthetic process can combine heterologous expression of a multipotent biosynthetic intermediate with multiple non-enzymatic steps to produce libraries of pseudo-natural products.

Marmycin A is an anthraquinone natural product with antiproliferative properties. Now the chemical synthesis of marmycin A—through a Diels–Alder cycloaddition, an Ullmann aromatic amination and a Friedel–Crafts cyclization—has enabled a study of its biological activity. Fluorescence microscopy reveals that marmycin A accumulates in lysosomes and promotes cell death independently of genome targeting.

Formaldehyde is universally employed in the fixation of tissue specimens, where it forms adducts with biomolecules, but this hinders the analysis of nucleic acids in the specimen. Bifunctional organocatalysts that speed the reversal of formaldehyde adducts of RNA and DNA are now reported, and show promise for general use in clinical specimens.

Christoph E. Düllmann reflects on the excitement, and implications, of probing the reactivity of heavy element seaborgium.