Polymers with potential: Poly(phosphoester)s play an important role in nature (DNA, RNA, and pyrophosphates), but in contrast to classical polyesters they are rarely used for everyday applications. Recent developments are highlighted that may make phosphorus-based polymers attractive materials for future applications.

Half a century after Schill and Lüttringhaus carried out the first directed synthesis of a [2]catenane, a plethora of strategies now exist for the construction of interlocked molecular rings. Effective template synthesis enables the synthesis of higher order interlocked systems. This Review outlines the diverse strategies that exist for forming catenanes, their applications, and the important challenges that remain in the field of chemical topology.

A bottom-up strategy is used to generate porosity from non-porous, one-dimensional, amorphous polymeric materials by their transformation into crystalline polyMOF materials. These materials harness the advantages of the porosity and crystallinity of MOFs along with certain attributes of the polymers, such as facile film formation and greater chemical stability.

Transpeptidase domains of penicillin binding proteins catalyze the incorporation of exogenous D-amino acids onto bacterial cell surfaces. The substrates can have diverse side chains (see picture, pink), and this promiscuous enzyme can also accommodate C-terminus variations (blue). Most importantly, fluorescence labeling differences within and between bacterial species could be profiled using a panel of compounds.

Surface-confined d–f bimetallic 2D coordination nanosystems have been achieved by using a three-step procedure that exploits orthogonal coordination interactions of CN-functionalized free-base porphyrin linkers with rare-earth and transition-metal centers. By systematic STM investigations the assembly process was established and the resulting nanoarchitectures characterized at the molecular level.

Freezing-induced mechanochemistry: A new diarylbibenzofuranone-based mechanophore showed reversible color change by external forces through radical mechanism. By incorporating the mechanophore into polymer chains, it was revealed that freezing gels induced mechanical force along the chains, but the force was not large enough to cleave common covalent bonds.

A solid-phase approach is proposed for highly efficient labeling (see picture, orange) of saccharides (blue) by using boronic acid (green) functionalized mesoporous silica nanoparticles as a nanoreactor. Compared to conventional liquid-phase labeling, the solid-phase approach exhibited faster reaction speed (only 2 min), high product purity, and much lower applicable saccharide concentration (10⁻⁹ M).

Short and sweet: Very short total syntheses of ellagitannins were achieved through sequential and regioselective functionalization of the hydroxy groups of unprotected glucose.

Two birds with one stone: Two classical antiaromatic molecules, cyclobutadiene and pentalene, were stabilized by introducing one metal fragment by a [2+2] cycloaddition reaction of osmapentalyne with alkynes. These metalla-aromatic molecules absorb broadly from the UV to the near-IR region and show significant photoacoustic and photothermal effects.

Just a pinch: CO₂ is efficiently hydrogenated for N-formylation of various amines using ruthenium-pincer catalysts, thus affording the corresponding formamides with extremely high turnover numbers (TONs). The catalyst was readily reused for 12 runs without significant loss of activity in N,N-dimethylformamide production, thus demonstrating potential for practical utilization of this cost-effective process.

Caught in the middle: A series of diamond-like supramolecular frameworks featuring mesoporous cavities have been assembled through multiple interactions (covalent bonds, dative bonds, and weak CH⋅⋅⋅X (X=O, F, and π) hydrogen bonds) between metal-imidazolate coordination cages and various anions. The mesoporous cavities are large enough to trap organic dye molecules, coordination cages, and vitamin B₁₂.

A novel general strategy was used for precise distance measurements on an outer membrane protein in whole E. coli cells and isolated outer membranes. This approach provides an elegant way to study conformational changes or protein–protein/ligand interactions under native conditions and provides a method to validate high-resolution structures of membrane proteins in their native environment.

Selective laser sintering has been used to prepare synthetic materials from a new type of self-immolative polymer. These materials autonomously amplify macroscopic and nonlocalized changes in the material in response to specific molecular inputs, and alter the response of the material depending on the identity of an applied signal.

A dielectric constant transition is observed in (HPy)₂[Na(H₂O)Co(CN)₆] (HPy=pyridinium cation). This transition is chemically triggered by water in a single-crystal-to-single-crystal transformation (see picture; right) and thermally switched (left) in a structural phase transition.

Heterostructures of semi-metallic CoSe₂ nanorods and p-Si microwires behave as an efficient photocathode for the solar-driven hydrogen evolution reaction. Photocurrents as high as 9 mA cm⁻² have been achieved at 0 V vs. reversible hydrogen electrode. The high photocurrents can be attributed to low charge transfer resistance between the Si and CoSe₂ interfaces and between the CoSe₂ and electrolyte interfaces.

BRD7 and BRD9 are bromodomain proteins and part of some chromatin-remodeling complexes. A fragment lead was rapidly optimized through structure-based design and exploitation of a stereoselective nitro-Mannich/lactamization cascade process to give the first potent and selective BRD7/9 inhibitor, LP99. Treatment with LP99 led to displacement of BRD7 and BRD9 from chromatin and down-regulation of the pro-inflammatory cytokine IL-6.

In pentacene films singlet-fission-induced nonlinear optical response with a magnitude of nonlinear susceptibility up to 10⁻⁹ esu is observed. Such efficient nonlinear optical response has been successfully applied to demonstrate ultrafast optical switching.

Put a ring on it: The insertion of two benzene moieties at the meso positions of a porphycene framework yields meso-dibenzoporphycene (mDBPc). The compound has a small electrochemical HOMO–LUMO gap (0.81 eV) and an NIR absorption band at 1047 nm. X-ray photoelectron spectroscopy and a theoretical study indicate that, unusually for a porphycene derivative, the cis tautomeric form of the porphycene framework is more stable than the trans form.

A nano-spiderweb: The complexation of multivalent terpyridine ligands with Cd^II ions afforded various linker-dependent ring-in-ring structures. The two-step self-assembly process through a tetratopic intermediate was deciphered by a mechanistic study. This ligand design strategy was successfully utilized in the construction of a trilayered metallo-supramolecular spiderweb.

The direct aldol reaction of an α-azido 7-azaindolinylamide is promoted by a Cu-based catalyst. Aromatic aldehydes bearing an ortho substituent exhibited diastereodivergency depending on the nature of the chiral ligands used. A vicinal azido alcohol unit led to the corresponding aziridine, and facile hydrolysis of the 7-azaindolinylamide moiety furnished enantioenriched β-hydroxy-α-azido carboxylic acid derivatives.

Directed although indirect: The antibiotic dihydrocineromyin B is one of countless natural products featuring an E-configured 2-methylbut-2-en-1-ol substructure (see picture, RCAM=ring-closing alkyne metathesis). The key step in the synthesis was a ruthenium-catalyzed hydroxy-directed trans-hydrostannation of an alkyne. The method is efficient, broadly applicable, and suited to late-stage diversification.

Hydrogenases mediate the conversion of H₂ into hydride and protons. Intermediates and transition structures for H₂ activation and hydride transfer in [Fe] hydrogenase were investigated (see picture, with a side-on bound dihydrogen and a hydride intermediate). Inclusion of the full protein with QM/MM is mandatory because of large electrostatic effects that cannot be described properly by vacuum calculations or continuum models.

Split and polished: Electrodeposited cobalt-phosphorous-derived films (Co-P) can act as superior bifunctional catalysts for overall water splitting. When employed as catalysts on both the anode and cathode for water electrolysis, the Co-P/Co-P catalyst couple can rival the integrated performance of IrO₂ and Pt in alkaline media. Such a bifunctional Co-P film is a promising catalyst candidate for overall water-splitting electrolysis.

How gallant: The catalytic asymmetric total synthesis of both (−)-galanthamine and (−)-lycoramine were achieved by using a conceptually new strategy. Two metal-catalyzed reactions were used as the key steps, and include a palladium-catalyzed intramolecular Larock annulation reaction and enantioselective conjugate addition reaction catalyzed by a Sc^III/N,N′-dioxide complex. Boc=tert-butoxycarbonyl, TES=triethylsilyl.

The hunt for high energy: Derivatives of 4,4′-bis(5-nitro-1,2,3-2H-triazole) were synthesized by different functionalization strategies. Competitive detonation properties were achieved and compared to reported analogues of fully carbon-nitrated bis(azole) compounds.

Dressing up phosphorus: The title reaction of N-(o-bromoaryl)-diarylphosphinic amides is described for the synthesis of phosphorus compounds bearing a P-stereogenic center. The method provides good enantioselectivities and high yields. The products were readily transformed into P-chiral biphenyl monophosphine ligands.

Grinding a rainbow: A purely organic compound with excellent room-temperature fluorescent–phosphorescent dual-emission (rFPDE) properties brought about by mechanical grinding has been demonstrated. It shows linearly tunable emission colors with a straight line across the white zone in the chromaticity diagram, following the principle of color mixing.

Fast and reversible ligand-assisted ammonia activation on a nickel-NCN pincer complex featuring a non-innocent N-heterocyclic carbene produced a solvent-dependent equilibrium mixture of ammine and amide complexes (see scheme, Dipp=2,6-diisopropylphenyl). These species were present in solution in comparable proportions, and EXSY NMR experiments as well as exchange with ND₃ further supported the equilibrium.

Double duty: Amphiphilic antibacterial aminoglycosides with additional immunomodulatory properties similar to those of host-defense peptides can be generated by appending a lipophilic R group (blue oval) to tobramycin. These amphiphilic tobramycin analogues can boost innate immune responses and control inflammatory responses related to septic shock.

A reagent with two hats: A highly efficient and general singlet-oxygen-initiated one-pot transformation of readily accessible furans into 5-hydroxy-1H-pyrrol-2(5H)-ones was developed (see scheme, right) and extended to the synthesis of other high-value α,β-unsaturated γ-lactams. This useful set of transformations relies on both the photosensitizing ability and the redox properties of methylene blue (MB), the reactivity of which differs from that of Rose Bengal (RB).

Stereoselective cycles: A Nazarov-type Pd⁰-catalyzed asymmetric cyclization is reported. The reaction forms cyclopentenones as single diastereoisomers that incorporate two contiguous asymmetric centers in high yield and optical purity. The optimized ligand L incorporates a weakly coordinating pyridine ring into a TADDOL-derived phosphoramidite. dba=dibenzylideneacetone. MS=molecular sieves.

A field day: The large π-conjugated N-heteroquinone 6,10,17,21-tetra[(triisopropylsilyl)ethynyl]-5,7,9,11,16,18,20,22-octaazanonacene-8,19-dione (OANQ; see figure) has been successfully synthesized and characterized. A field-effect transistor device based on OANQ single crystals displays an electron mobility of up to 0.2 cm² V⁻¹ s⁻¹ under ambient conditions.

Going strong: Sol engineering of graphitic carbon nitride solids with strong oxidizing acids (e.g. HNO₃) generates a stable colloidal suspension, which can be translated into thin films by dip/disperse-coating techniques. The polymeric matrix and the reversible hydrogen bonding result in the thin-film electrodes derived from the sol solution having high mechanical stability with improved conductivity for charge transport.

Nontoxic: Acrylic acids are an important chemical feedstock. The title reaction provides acrylic acid and derivatives in good yields with high regioselectivities without the need to handle toxic CO gas.

Without a trace…︁ A highly stereoselective cycloaddition strategy provided efficient access to a diverse array of 5-unsubstituted pyrrolidines and enabled a five-step total synthesis of isoretronecanol (see scheme). A novel role of sodium borohydride in reductive decyanation was observed.

Doubled over: Chlorination of β-haloporphyrins with 2-chloro-1,3-bis(methoxycarbonyl)guanidine (Palau'Chlor) proceeded selectively at the neighboring unsubstituted meso position to afford meso,β-oligohaloporphyrins, which are useful intermediates of porphyrin-based extended π systems. For example, meso-chloro-β-iodoporphyrin was transformed stepwise into an efficiently conjugated meso-to-meso,β-to-β doubly butadiyne-linked porphyrin dimer.

Reactivity trend reversal: Methylenephosphonium salts coordinated to a manganese center were found to exhibit “iminium-like” reactivity towards nucleophiles (see scheme). This unprecedented umpolung enables the instant formation of carbon–heteroatom bonds, highlighted by the synthesis of novel chiral pincer-type phosphine–NHC–phosphine ligands.

Gentle persuasion: A quinine-derived thiourea organocatalyst was found to promote the asymmetric addition of naphthols and activated phenols to ketimines derived from isatins (see scheme; Boc=tert-butoxycarbonyl). The reaction under mild conditions afforded chiral 3-amino-2-oxindoles containing a quaternary stereocenter in high yields (up to 99 %) with excellent enantioselectivity (up to 99 % ee).

Boosting HER activity by phosphorus modification of tungsten nitride/reduced graphene oxide leads to a low-cost, high-performance, non-noble metal electrocatalyst for the hydrogen evolution reaction. The catalyst has a very small onset overpotential, a low Tafel slope, a large exchange current density in acid, and was stable in accelerated durability testing.

That's great, DEER! When a double-histidine Cu²⁺-binding motif (shown in blue) assembled in situ from natural amino acid residues and a metal salt was used as a rigid spin probe for double electron–electron resonance (DEER) distance measurements, dramatically narrower and readily interpretable distance distributions were observed than with a commonly used flexible spin label (red). Molecular modeling of an unlabeled protein gave a distance within 0.5 Å of the experimental value.

Fox in a box: New derivatives created from 1,1-diamino-2, 2-dinitroethene (FOX-7) often have properties superior to those of RDX. The compounds exhibit good thermal stability, high density, positive heats of formation, an acceptable oxygen balance, and excellent detonation properties. These findings contribute to the value of FOX-7 as an energetic precursor.

Keeping score: Nucleic acid sequences and sequence counts were used as multivariate data without the necessity of a spatial array. Aptamers were used as semi-specific receptors for cell line differentiation, and cross-reactivity between the aptamers was observed. The principal component analysis (PCA) generates high-dimensionality score plots, thus differentiating a mixture of complex and subtly different analytes.

Zirconocene-based AlMe₃ adducts bind an additional AlMe₃ molecule reversibly, affording heterotrimetallic intermediates. One of the AlMe₃ adducts undergoes slow decomposition via CH activation in a bridging methyl unit to yield a new species with a trimetallic {Zr(μ-CH₂)(μ-Me)AlMe(μ-Me)AlMe₂} core.

Azo borealis: The first 1,2-azaborinine-substituted azo dyes have been synthesized using sterically demanding boroles and organic azides. The ring-expansion mechanism of the unexpected formation of the bright yellow chromophores was investigated by DFT calculations.

Inexpensive cobalt catalysis enabled the CH alkenylation of unactivated (hetero)arenes with enol derivatives at ambient temperature. The versatile cobalt catalyst was employed for challenging CH/CO cleavage reactions with alkenyl acetates, carbamates, carbonates, and phosphates in a stereoconvergent fashion.

Crystal contact. A calixarene “molecular glue” (blue) can be used to grow crystals of cytochrome c (gray; heme red) directly on Au–SAM electrodes. Characterization by cyclic voltammetry revealed remarkable electroactivity in the crystals. The amount of electrode-addressable protein is several orders of magnitude larger than in standard multilayer systems.

Ammonize me! The first compound in the class of ammine borates has been synthesized by a multi-anvil high-pressure/high-temperature experiment. The previously unknown adduct of ammonia to an inorganic BO₃ group of a borate can be stabilized with this method, resulting in a BO₃(NH₃) tetrahedron as a new structural element.

Polyhydroxycarboxylic acid for nanoscale carrier formation: By ring-opening polymerization with high regioselectivity, a polyester (BICpoly) is obtained which can be precipitated in water as nanoparticles or as a thin film. Its complete stability at low pH values, its residue-free hydrolysis to biocompatible monomers at higher pH values, and its capability for drug loading and sustained drug release, make BICpoly an attractive carrier material for medical applications.