Photons trapped in a superconducting cavity constitute an ideal system to realize some of the thought experiments imagined by the founding fathers of quantum physics. Physics laureate S. Haroche gives a personal account of the experiments performed with this “photon box” at the Ecole Normale Supérieure.

Experimental control of quantum systems has been pursued widely since the invention of quantum mechanics. Today, we can in fact experiment with individual quantum systems, deterministically preparing superpositions and entanglements. In his Nobel lecture, D. J. Wineland gives an overview of this research which has led to the Nobel prize in physics in 2012.

Two of a kind: Two agostic isomers of [CpMo(CO)₂(PiPr₃)]⁺ B(C₆F₅)₄⁻ have been isolated. Both were characterized in the solid state by X-ray crystallography and spectroscopic techniques, and also by DFT calculations. Significantly different LUMO energies cause the difference in color (blue versus orange, see picture) of these isomers.

The proton did it! Tetrahydrobenzodifurans have been synthesized through the trifluoromethanesulfonic acid (HOTf) catalyzed direct oxidative CH functionalization of benzoquinone with olefins. A variety of substituents were found to be tolerated, and a synergetic oxidative/[3+2] cyclization mechanism was proposed based on the experimental results.

The long and the short of it. The first amido–digermyne to possess a short Ge–Ge multiple bond, [LGeGeL], has been prepared and shown to activate H₂ below 0 °C, thereby yielding the hydrido–digermene, [L(H)GeGe(H)L]. This possesses a very long GeGe bond. Spectroscopic and theoretical data indicate that the dimer dissociates in solution to give the two-coordinate hydrido–germylene, [:Ge(H)(L)]. L=N(Ar)(SiiPr₃), Ar=2,6-[C(H)Ph₂]₂-4-iPrC₆H₂.

Dehaloperophoramidine, the dehalogenated analogue of the marine hexacyclic alkaloid perophoramidine was synthesized. The intramolecular nucleophilic dearomatizing arylation of aminoquinoline initiated by a lithium–iodine exchange and the subsequent direct allylation of the resultant azaenolate afforded a pentacyclic bisamidine compound bearing two contiguous all-carbon quaternary centers in good yield with excellent diastereoselectivity.

Magnetic levitation (MagLev) provides a simple method for the separation of crystal polymorphs that differ in density (Δρ) by greater than 0.001 g cm⁻³. Density-based separations of multiple crystalline forms were shown for four organic compounds: 5-methyl-2-[(2-nitro- phenyl)amino]-3-thiophenecarbonitrile, sulfathiazole, carbamazepine, and trans- cinnamic acid.

Making heads or tails of it: A strategy involving a head-to-tail imine-captured ring closure followed by ring contraction was used to synthesize otherwise difficult cyclic tetrapeptides. Compared with the direct lactamization process, the estimated activation energies for the cyclic imine formation and the ring contraction were lowered by 7.3 and 7.6 kcal mol⁻¹, respectively, which enables cyclization.

Tuning the electronics of nanotubes: Electron-accepting 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) nanotweezers endowed with a carboxylic acid-containing dendrimeric moiety form exceptionally stable n-/p-type dispersions with single-walled carbon nanotubes (SWCNTs) in water. Upon photoexcitation, the nanohybrids undergo a less common electron transfer from the SWCNTs to the TCAQ nanotweezers (see picture).

To fold or not to fold? It is shown that attached sugars play a defining role in the conformations adopted by a pair of novel SAA-derived foldamers in water and that these differences are reflected in the contrasting interactions of these glycofoldamers with various biological targets. C green, O red, N blue, H gray; yellow oval=mannose.

Acid instead of base: Kinetic resolution of secondary alcohols is realized using chiral Brønsted acid catalyzed acylation instead of the conventional basic conditions. A broad range of functional groups are tolerated, such as aldehydes, carboxylic acids, and enoates. The selectivity factor (s) reaches up to 215 at ambient temperature.

Picking up the thread: The macrocycle bis-p-xylyl[26]crown-6 is capable of forming pseudorotaxane-like structures with single, nonconjugated urea or amide moieties when assisted by templating Na⁺ ions (see example). By using this approach, rotaxanes were synthesized with glycine residues or the repeating unit of nylon-6,6 as key components in the threadlike units.

Frozen but flexible: The conformational flexibility of calixarene molecules is not only limited to solution. It can also manifest itself in single crystals as a response to the right external stimuli.

No catalyst required! A highly efficient, catalyst-free process to generate diimide in situ from hydrazine monohydrate and molecular oxygen for the selective reduction of alkenes has been developed. The use of a gas–liquid segmented flow system allowed safe operating conditions and dramatically enhanced this atom-economical reaction, resulting in short processing times.

Catalytic asymmetric α-arylation of N-unprotected 3-substituted oxindoles with diaryliodonium salts has been realized by a chiral Lewis acid promoted electrophilic addition and aryl-rearrangement process. Single C3-arylated products containing a quaternary carbon center were generated in high enantioselectivity and reactivity.

Why is it π? The first X-ray crystal structure of a cuprate–carbonyl π-complex has been obtained for the intermediate prepared from Me₂CuLi and fluorenone (see scheme). It is also the first structure of a π-complex between an organocuprate and a double bond of any kind.

Formaldehyde detectives: Evidence for the production of formaldehyde during a ruthenium-catalyzed CO₂ reduction process, and for its involvement in the formation of the resulting C₂ compound, is disclosed. Ultimately, formaldehyde can be recovered by methanol trapping. HBPin=pinacolborane.

Give me five: Group VI metal quintuple bonds undergo Friedel–Crafts-type haloacylation reactions. Treatment of the quintuple-bonded molybdenum complexes with one equivalent of acyl halides RCOX (R=Me, C₆H₅, 2-MeC₆H₄; X=Cl, Br), yields metal–metal quadruple-bonded acyl complexes. Subsequent treatment with a second equivalent of acyl halides causes disproportionation of two acyl groups to give dimolybdenum carbyne carboxylate complexes.

In the reaction zone: Reaction of an aryltriazene with acid generates the corresponding aryldiazonium ion. When this reaction takes place in the mixing zone, at the interface between two streams flowing laminarly and in parallel through a 100 μm microchannel, a submicrometer line of organic film is grafted at the substrate surface.

In the frame: A cascade sequence combining an asymmetric Henry reaction and a stereoselective intramolecular iodocyclization provides direct access to an enantioenriched tricyclic hexahydrochromeno[4,3-b]pyrrole framework (see scheme). The Henry reaction is catalyzed by copper in the presence of L1.

An anionic three-way switch: A bipyridyl bis(urea)-based anion receptor that is highly selective for dihydrogen phosphate demonstrates spectroscopically distinct anion-bound conformations toward halides and select oxoanions. ¹H NMR studies show the differing anion-induced conformations are reversible allowing this system to function as a three-way molecular switch.

New tripodal urea receptors demonstrate preferential binding of anions over competitive hydrogen bonding solvents. ¹H NMR titrations in 10 % [D₆]DMSO/CDCl₃ show a higher affinity for nitrate over the halides for the fluorinated receptor, which is lost when the fluorine atoms are absent. An anion–π interaction between the nitrate and the π-system of the ethynyl-substituted arene is proposed as the source of this selectivity.

Not only σ*σ but also σ*π: High-level electronic structure calculations reveal the σ*σ and σ*π bonding patterns for Au^I–Au^I bonding in excited states and suggest two conformation-dependent photophysical relaxation mechanisms for dicyanoaurate oligomers (n=2–5; see picture) in aqueous solution. These insights into the excited-state electronic structure should also be relevant for other gold complexes with a similar gold scaffold.

Tracking the target: To identify a protein that binds directly to the HIF-1α inhibitor LW6, a series of new chemical probes were synthesized with a clickable tag and/or a photoactivatable moiety. LW6 was found to be localized to the mitochondria (see picture) and MDH2 was identified as a target protein of LW6. These results indicate that the HIF-1α inhibitory activity of LW6 is a consequence of MDH2 suppression.

Distance measurements: Pulsed EPR distance measurements combined with strategic spin labeling provide structural constraints at the molecular level for the fold of α-synuclein in amyloid fibrils (see picture; r=distance). The detection of interstrand distances in fibrils will potentially make it possible to extend these measurements to oligomeric states of these protein families.

Pumped up: Building an autoinductive, self-propagating reaction directly into a polymer has resulted in stimuli-responsive materials that are capable of remembering the presence of a stimulus, even after the stimulus is no longer present. As a proof of concept, a nonmechanical, polymer-based pump has been made that is capable of pumping fluids surrounding the polymer when exposed to a fleeting signal (UV light, see picture).

On-surface polymerization is feasible on semiconducting surfaces. Thermally triggered covalent coupling of 10,10′-dibromo-9,9′-bianthryl molecules on the TiO₂(011)-(2×1) surface is demonstrated. The result paves the way for application of the thermally driven on-surface polymerization on semiconducting surfaces and indicates that methods based on such a reaction are more universal than previously thought.

Outside thermodynamic equilibrium, outcomes of self-assembly can be dictated not by energy but by the energy dissipation rate. Remarkably, non-equilibrium self-assembly can lead to both low- and high-dissipation structures. The latter, thermodynamically more wasteful structures are exponentially less probable with increasing dissipation rate. This dependence is quantified in a Boltzmann-like relation for non-equilibrium systems.

A universal alignment medium for the measurement of anisotropic NMR parameters that can be used for almost any type of sample would be highly useful for structure analysis in solution. Cross-linked poly(ethylene oxide) with incredible solvent and solute compatibility range provides this medium. The picture shows residual ¹⁵N chemical shift anisotropies (RCSAs) of ¹⁵N-labeled ubiquitin.

A zwitterionic construction has been synthesized that covalently links a trialkylsilylium cation and a weakly coordinating carborane anion in one neutral molecule (see X-ray structure; Si green, C gray, B orange, Cl red). The silylium character of this molecule is supported by DFT calculations (see LUMO), ²⁹Si CP/MAS NMR spectroscopy, and reactivity.

One flue over the cuckoo's nest: A novel porous Zr-based MOF combining a high chemical stability, easy “green” synthesis and scalability is prepared. This material incorporating carboxylic functions on its organic linkers has thermodynamically and kinetically very promising properties for CO₂ capture from post-combustion flue gas under real working conditions.

An EmrE-ging market: Oriented solid-state NMR spectroscopy and biochemical cross-linking experiments were used to show that the ligand-free membrane protein transporter EmrE forms anti-parallel dimers with different monomer tilt angles relative to the lipid bilayer. In addition, subtle conformational changes were detected upon drug binding that emphasize the need for an atomic-resolution structure.

Semiconducting polymer nanoparticles are used as a free-radical inert and light-harvesting nanoplatform for in vivo molecular imaging of reactive oxygen and nitrogen species (RONS). This nanoprobe permits detection of RONS in the microenvironment of spontaneous bacterial infection (see picture; FRET=fluorescence resonance energy transfer).

Weight lifting: A polymer-based device capable of lifting many times its own mass was fabricated by drying a solution of the polycation poly(diallyldimethyl ammonium chloride) (pDADMAC) on a surface coated with charged poly(N-isopropylacrylamide)-based microgels. Upon drying of the pDADMAC solution on the microgel-modified surface, it bends. Flexible surfaces then curl up into scroll-like structures, which can be opened up at high humidity.

In case of emergency, break glass: Biohybrid core/shell capsules (see picture) suitable for encapsulation of volatile molecules can be formed through precipitation of amorphous silica in a protein/polyanion coacervate scaffold. The coacervate molds the final shape and structure of the capsule shell and provides an acidic microenvironment to locally induce hydrolysis and condensation of liquid silica precursors.

Let the Fur fly: Mutation of a single glutamate into an aspartate was shown to make the Fe sensor Fur as reactive to H₂O₂ as the peroxide sensor PerR. In vivo and in vitro peroxide sensitivities of a series of PerR and Fur Asp/Glu mutants were studied by mass spectrometry. A combination of Mössbauer spectroscopy analyses and DFT calculations gave a structural rationale for this behavior.

More than skin deep: A selective silica coating on the ends and side of gold nanorods enables the successful selective overgrowth of palladium, gold, platinum, and silver on these surfaces. As a result, eight types of unprecedented metal homo- and heterostructures are produced.

Building a better dehydrator: A nanocomposite catalyst was designed and synthesized expressly for the dehydration of fructose to the platform chemical, 5-hydroxymethylfurfural (HMF). When poly(vinylpyrrolidone) is intercalated and cross-linked inside the acid-functionalized mesopores of silica, the fructose tautomer equilibrium favors HMF production.

Getting more for less: In the presence of H₂ and a base, air- and moisture-tolerant Ru^II complexes catalyze the hydrogenation of ketones and aldehydes with excellent activity and chemoselectivity, and with enantioselectivity of up to 95 % under mild conditions. The ratio of substrate to catalyst can be lowered to 10⁶:1. The reactions tolerate scale-up and can be carried out with almost no solvent. A base-free method is available for base-sensitive substrates.

Transport forces: To move molecules across the nuclear envelope they have to overcome the selective barrier of the nuclear pore which is formed by nucleoporins (nups) with FG repeats. The molecules are chaperoned by shuttling receptors that interact with FG nups thereby passing the barrier using an unresolved mechanism. This process is explored by single-molecule force spectroscopy (see picture).

Sensor selectivity: Selective detection of individual vapors and their mixtures is achieved by using a single three-dimensional networked film of organothiol-functionalized plasmonic nanoparticles (see picture). This approach gives a new perspective for sensing, where tunable selectivity is achieved within a single sensing film, rather than from an array of separate conventional sensors.

The smallest piano stool [CpNa(NH₃)₃] is not a stand-alone unit in the solid state but is largely shaped by strong intermolecular NH⋅⋅⋅π interactions. Small but important structural features, such as the bending of the CH bonds inwards to the sodium atom that was confirmed by experimental charge density investigations, could only be reproduced by quantum mechanical calculations that included a lattice of more than 300 units.

The other double helix: The molecular structure of double-stranded poly(rA) was predicted in 1961, but it has only now been confirmed. The crystal structure of the parallel double helix of (rA)₁₁ obtained at physiological pH was solved using ab initio direct methods and refined to 1.0 Å resolution. The crystals have bound ammonium ions that are complexed by the RNA phosphates and adenine N1 atoms (see section of the structure).

The binding energies of O₂ and CO to iron(II) and manganese(II) porphyrin anions has been determined in the gas phase. Low-pressure ion–molecule equilibria have been measured in a cryogenically cooled trap of an FT-ICR mass spectrometer, and binding energies of (40.8±1.3) kJ mol⁻¹ and (66.3±2.6) kJ mol⁻¹ have been obtained for oxygen and carbon monoxide, respectively, with a heme-analogue Fe^II porphyrin complex.

The selective incorporation of N-methyl groups in the highly amyloidogenic and cytotoxic sequence of the type 2 diabetes islet amyloid polypeptide (IAPP) generates a unique class of soluble and nontoxic IAPP mimics. These polypeptides combine potent IAPP receptor agonism with nanomolar-affinity inhibitory potential on the amyloid formation and cell-damaging effects of both IAPP and the Alzheimer's β-amyloid peptide (Aβ40).

Second site: In the crystal structure of human MALT1_casp-Ig3 (mucosa-associated lymphoid tissue lymphoma translocation protein 1) in complex with the tricyclic phenothiazine derivative thioridazine (violet in the picture), the inhibitor is bound in a hydrophobic pocket far from the active site. This explains the action of phenothiazine derivatives as noncompetitive, reversible inhibitors.