The cover image shows an artist's impression of cells growing in a photochemically modifiable hydrogel matrix. In the system described by Cole DeForest and Kristi Anseth, the hydrogel is formed using a biocompatible copper-free click reaction. It is then modified using a combination of two orthogonal photochemical reactions to investigate how cells spread and form interactions in response to various biochemical and biomechanical stimuli during growth.Article p925IMAGE: ERIC CLAEYS, COLE DEFOREST & KRISTI ANSETHCOVER DESIGN: ALEX WING

The cover image shows an artistic impression of the flow of energy in the wake of the solution-phase bimolecular reaction between cyclohexane and the cyano radical. This reaction was studied by David Glowacki, Jeremy Harvey and co-workers using molecular dynamics simulations to model the vibrational relaxation of the products. The more intense colours indicate fast energy exchange within the radical co-product solvent shell, whereas less intense colours indicate slower energy flow once the products have diffused away from one another within the solvent.Article p850IMAGE: BECCA ROSE AND DAVID GLOWACKICOVER DESIGN: ALEX WING

The cover shows a dynamic supramolecular system built by Sugawara and co-workers, in which the self-reproduction of vesicle compartments is linked to the replication of encapsulated DNA. Externally added membrane precursors are taken up by the vesicles and converted into membrane molecules, enabling the vesicles to grow and divide. Vesicles within which DNA is amplified undergo rapid and sequential divisions, distributing newly formed DNA to daughter vesicles. This represents a promising approach for the construction of a minimal cell.Article p775IMAGE: NEWTON PRESS, JAPANCOVER DESIGN: ALEX WING

To mark the International Year of Chemistry and the hundredth anniversary of the award of the Nobel Prize in Chemistry to Marie Curie, this issue features a series of Commentary articles examining broader issues in chemistry beyond the science itself. As part of this collection, Michelle Francl considers how the representation of women in science has changed since Curie's day. The image on the cover comprises a mosaic of female scientists — many thanks go to them and also to Michelle who suggested the concept and collected most of the pictures.

More information about the cover can be found in this post on the Sceptical Chymist blog.

A higher resolution PDF file of the cover is available here.

Commentary p670;

Insight pp667–695

ORIGINAL IMAGE: PHOTOS.COM/THINKSTOCK

COVER DESIGN: ALEX WING

Metal–ligand interactions can be tuned by changing the carbon-based substituents on the ligand’s coordinating atom, but tuning electronics often means altering sterics too. On investigating icosahedral carboranes as alternative substituents, Mirkin and co-workers now show that, depending on their positional attachment, these boron-rich clusters can significantly vary from electron withdrawing to electron donating. The carborane–selenol derivative depicted on the cover exhibits a highly electron-rich environment at the selenium atom.

Article p590; News & Views p577

IMAGE: ALEX SPOKOYNY, NORTHWESTERN UNIV.

COVER DESIGN: ALEX WING

Despite the broad appeal of carbenes as ligands for metal complexes and as catalysts in their own right — typically in the form of N-heterocyclic carbenes — the isoelectronic nitrenium analogues have received much less attention. Now, Mark Gandelman and co-workers have prepared several N-heterocyclic nitrenium ions (one of which is shown conceptually on the cover) and examined their ligand properties. It is found that relatively strong metal–nitrenium bonds are formed and the ligands are shown to be poor σ donors and good π acceptors.

Cover design by Alex Wing, Nature Chemistry

Article p525

The cover shows an artist's impression of a microfluidic device developed by deMello and co-workers that, without any moving parts, captures and then dilutes droplets to produce a digital concentration gradient. Microfluidics offers great potential when performing chemical and biological experiments — such as DNA-binding assays — in a high-throughput fashion, but device complexity is often the 'elephant in the room'. This new device opens up the world of microfluidics to the kind of serial dilution that is routinely performed on the macroscale using a pipette.

Image hand-drawn by Claire Stanley/Cover design by Alex Wing, Nature Chemistry

Article p437

The cover image shows a surface-confined switch based on an electroactive organic radical (red) that is transformed to the corresponding anion (purple). This bistable system, developed by Jaume Veciana, Concepció Rovira and co-workers, behaves as an extremely robust redox switch in which an electrical input is transduced into an optical and magnetic output. This switch operates at very low voltages, can be patterned and locally addressed, and exhibits an exceptionally high long-term stability and excellent reversibility.

Image by Mateu Marcet/Cover design by Alex Wing, Nature Chemistry

Article p359

With the emergence of graphene, the rich and vivid chemistry of graphite intercalation compounds (GICs) has experienced a renaissance. Now, Andreas Hirsch and co-workers have designed a reaction that uses in situ-generated GICs (seen in the background of the cover image) to obtain covalently functionalized graphene from graphitic starting materials. The spatially demanding organic addends (as depicted in green and white on the cover) not only grant enhanced solubility but also serve as multipurpose chemical anchors.

Image courtesy of Frank Hauke/Cover design by Alex Wing, Nature Chemistry

Article p279

Organic compounds rarely exhibit phosphorescence, a property more commonly associated with inorganic or organometallic species. Now, Kim and co-workers have used a crystal-design strategy that relies on halogen bonding to combine the heavy-atom effect with triplet-state emission from aromatic carbonyls to produce high-quantum-yield phosphorescence from purely organic materials. The cover shows a snapshot of crystallization from the liquid phase where the emission of green light is activated as the crystals forms.

Cover design by Alex Wing/Nature Chemistry

Article p205

The interaction of diatomic molecules with complexed iron or cobalt centres is important in many biological processes. Notably, metallotetrapyrrole units carry respiratory gases or provide catalytic and sensing functions. Now, Barth and colleagues have used saddle-shaped Fe- and Co-porphyrins arranged on a surface as model systems to investigate their interaction with carbon monoxide. Molecular-level scanning tunnelling microscopy (STM) observations and density functional theory calculations reveal a novel cis-dicarbonyl bonding arrangement. The STM image on the cover shows both rod-shaped bare porphyrins and cross-like carbonyl species where CO selectively bridges specific bonds between metal centres and nitrogen.

Cover design by Alex Wing/Nature Chemistry

Article p114

The foundation for analytical techniques such as NMR spectroscopy and MRI is the precession of a quantum mechanical angular momentum vector about an applied magnetic field. Parker, Vallance, Zare and co-workers have now imaged this precessional motion in a model system of strongly polarized oxygen atoms. The cover displays coloured velocity-map images showing slices through an aligned distribution of excited-state oxygen atoms.

Cover design by Alex Wing/Nature Chemistry

Article p28