Sulfate-induced large amplitude conformational change in a Solomon link.

A doubly-interlocked [2]catenane - or Solomon link - undergoes a complex conformational change upon addition of sulfate in methanol. This transformation generates a single pocket where two SO anions bind through multiple hydrogen bonds and electrostatic interactions. Despite the close proximity of the two anions, binding is highly cooperative.

Intracluster ligand rearrangement: an NMR-based thermodynamic study.

Ligand and metal exchange reactions are powerful methods to tailor the properties of atomically precise metal nanoclusters. Hence, a deep understanding of the mechanisms behind the dynamics that rule the ligand monolayer is crucial for its specific functionalization. Combining variable-temperature NMR experiments and dynamic-NMR simulations, we extract the thermodynamic activation parameters of a new exchange reaction: the intracluster ligand rearrangement between the two symmetry-unique positions in [Ag(DMBT)] and [AgAu(DMBT)] clusters.

Influence of alkali metals on water dynamics inside imidazolium-based ionic liquid nano-domains.

The global need to expand the design of energy-storage devices led to the investigation of alkali metal - Ionic Liquid (IL) mixtures as a possible class of electrolytes. In this study, 1D and 2D Nuclear Magnetic Resonance (NMR) and Electrochemical Impedance Spectroscopy (EIS) as well as Molecular Dynamics (MD) simulations were used to study the intermolecular interactions in imidazolium-based IL - water - alkali halide ternary mixtures. The H and Na 1D and H DOSY NMR spectra revealed that the presence of small quantities of NaCl does not influence the aggregation of water molecules in the IL nano-domains.

Decoded fingerprints of hyperresponsive, expanding product space: polyether cascade cyclizations as tools to elucidate supramolecular catalysis.

Simple enough to be understood and complex enough to be revealing, cascade cyclizations of diepoxides are introduced as new tools to characterize supramolecular catalysis. Decoded product fingerprints are provided for a consistent set of substrate stereoisomers, and shown to report on chemo-, diastereo- and enantioselectivity, mechanism and even autocatalysis. Application of the new tool to representative supramolecular systems reveals, for instance, that pnictogen-bonding catalysis is not only best in breaking the Baldwin rules but also converts substrate diastereomers into completely different products.

Time-Dependent Hydrogen Bond Network Formation in Glycerol-Based Deep Eutectic Solvents.

The front cover artwork is provided by Patryk Palenque Marcinkowski. The image shows a glycerol-choline network accommodating water molecules over time. The glycerol molecules are represented as pandas adapting to the change.

Acetylene Derivatives of Cationic Diazaoxatriangulenes and Diaza [4]Helicenes - Access to Red Emitters and Planar Chiral Stereochemical Traits.

Cationic triangulenes, and related helicenes, constitute a rich class of dyes and fluorophores, usually absorbing and emitting light at low energy, in the orange to red domains. Recently, to broaden the scope of applications, regioselective late-stage functionalizations on these core moieties have been developed. For instance, with the introduction of electron-donating groups (EDGs), important bathochromic shifts are observed pushing absorptions towards or in the near-infrared (NIR) spectral domain while emissive properties disappear essentially completely.

Direct Solution-Based Synthesis of Na (B H )(B H ) Solid Electrolyte.

All-solid-state batteries (ASSBs) promise higher power and energy density than batteries based on liquid electrolytes. Recently, a stable 3 V ASSB based on the super ionic conductor (1 mS cm near room temperature) Na (B H )(B H ) has demonstrated excellent cycling stability. This study concerns the development of a five-step, scalable, and solution-based synthesis of Na (B H )(B H ).

SAN plot: A graphical representation of the signal, noise, and artifacts content of spectra.

The signal-to-noise ratio is an important property of NMR spectra. It allows to compare the sensitivity of experiments, the performance of hardware, etc. Its measurement is usually done in a rudimentary manner involving manual operation of selecting separately a region of the spectrum with signal and noise, respectively, applying some operation and returning the signal-to-noise ratio.

Synchronized On/Off Switching of Four Binding Sites for Water in a Molecular Solomon Link.

A molecular Solomon link adopts different conformations in acetonitrile (1) and in water (2). Contrary to expectations, the main driving force of the transformation is not the change in medium polarity, but the cooperative binding of about four molecules of water, forming a tiny droplet in the central cavity of 2. Mechanistic studies reveal that the four binding sites can simultaneously switch between an inactive state (unable to bind water) and an active state (able to bind water) during the transformation.

A Strategy to Synthesize Molecular Knots and Links Using the Hydrophobic Effect.

Conventional approaches to the synthesis of molecular knots and links mostly rely on metal templation. We present here an alternative strategy that uses the hydrophobic effect to drive the formation of complex interlocked structures in water. We designed an aqueous dynamic combinatorial system that can generate knots and links.

Imine-based [2]catenanes in water.

We report the efficient condensation of imine-based macrocycles from dialdehyde and aliphatic diamines in pure water. Within the libraries, we identified a family of homologous amphiphilic [2]catenanes, whose self-assembly is primarily driven by the hydrophobic effect. The length and odd-even character of the diamine alkyl linker dictate both the yield and the conformation of the [2]catenanes, whose particular thermodynamic stability further shifts the overall equilibrium in favour of imine condensation.

NMReDATA, a standard to report the NMR assignment and parameters of organic compounds.

Even though NMR has found countless applications in the field of small molecule characterization, there is no standard file format available for the NMR data relevant to structure characterization of small molecules. A new format is therefore introduced to associate the NMR parameters extracted from 1D and 2D spectra of organic compounds to the proposed chemical structure. These NMR parameters, which we shall call NMReDATA (for nuclear magnetic resonance extracted data), include chemical shift values, signal integrals, intensities, multiplicities, scalar coupling constants, lists of 2D correlations, relaxation times, and diffusion rates.

Synergistic Anion-(π) -π Catalysis on π-Stacked Foldamers.

In this report, we demonstrate that synergistic effects between π-π stacking and anion-π interactions in π-stacked foldamers provide access to unprecedented catalytic activity. To elaborate on anion-(π) -π catalysis, we have designed, synthesized and evaluated a series of novel covalent oligomers with up to four face-to-face stacked naphthalenediimides (NDIs). NMR analysis including DOSY confirms folding into π stacks, cyclic voltammetry, steady-state and transient absorption spectroscopy the electronic communication within the π stacks.

Targeted Isolation of Monoterpene Indole Alkaloids from Palicourea sessilis.

Phytochemical investigation of the alkaloid extract of Palicourea sessilis by LC-HRMS/MS using molecular networking and an in silico MS/MS fragmentation approach suggested the presence of several new monoterpene indole alkaloids. These compounds were isolated by semipreparative HPLC, and their structures confirmed by means of HRMS, NMR, and ECD measurements as 4-N-methyllyaloside (3), 4-N-methyl-3,4-dehydrostrictosidine (4), 4β-hydroxyisodolichantoside (6), and 4α-hydroxyisodolichantoside (7), as well as the known alkaloids alline (1), N-methyltryptamine (2), isodolichantoside (5), and 5-oxodolichantoside (8). In addition, the acetylcholinesterase inhibitory activity of the compounds was evaluated up to 50 μM.

Enolate Stabilization by Anion-π Interactions: Deuterium Exchange in Malonate Dilactones on π-Acidic Surfaces.

Of central importance in chemistry and biology, enolate chemistry is an attractive topic to elaborate on possible contributions of anion-π interactions to catalysis. To demonstrate the existence of such contributions, experimental evidence for the stabilization of not only anions but also anionic intermediates and transition states on π-acidic aromatic surfaces is decisive. To tackle this challenge for enolate chemistry with maximal precision and minimal uncertainty, malonate dilactones are covalently positioned on the π-acidic surface of naphthalenediimides (NDIs).

Discrimination of hexabromocyclododecane from new polymeric brominated flame retardant in polystyrene foam by nuclear magnetic resonance.

Hexabromocyclododecane (HBCDD) is a brominated flame retardant (BFR) and major additive to polystyrene foam thermal insulation that has recently been listed as a persistent organic pollutant by the Stockholm Convention. During a 2013/2014 field analytical survey, we measured HBCDD content ranging from 0.2 to 2.

New prostaglandin analog formulation for glaucoma treatment containing cyclodextrins for improved stability, solubility and ocular tolerance.

Latanoprost is a practically insoluble prostaglandin F2α analog considered a first-line agent for glaucoma treatment. From a pharmaceutical point of view, latanoprost is challenging to be formulated as an eye drop due to its poor water solubility and the presence of an ester bond that needs to be cleaved in vivo but maintained unchanged during storage. Cyclodextrins (CDs) are known to form complexes with hydrophobic drugs, influencing their stability, availability, solubility, and tolerance in a non-predictable manner.

Non-linear effects in quantitative 2D NMR of polysaccharides: pitfalls and how to avoid them.

Quantitative 2D NMR is a powerful analytical tool which is widely used to determine the concentration of small molecules in complex samples. Due to the site-specific response of the 2D NMR signal, the determination of absolute concentrations requires the use of a calibration or standard addition approach, where the analyte acts as its own reference. Standard addition methods, where the targeted sample is gradually spiked with known amounts of the targeted analyte, are particularly well-suited for quantitative 2D NMR of small molecules.

Enantioselective halogenative semi-pinacol rearrangement: extension of substrate scope and mechanistic investigations.

The present Full Paper article discloses a survey of our recent results obtained in the context of the enantioselective halogenation-initiated semi-pinacol rearrangement. Commencing with the fluorination/semi-pinacol reaction first and moving to the heavier halogens (bromine and iodine) second, the scope and limitations of the halogenative phase-transfer methodology will be discussed and compared. An extension of the fluorination/semi-pinacol reaction to the ring-expansion of five-membered allylic cyclopentanols will be also described, as well as some preliminary results on substrates prone to desymmetrization will be given.

Enantioselective halogenative semi-pinacol rearrangement: a stereodivergent reaction on a racemic mixture.

An efficient, quantitative deracemization strategy for optically inactive allylic cycloalkanols has been achieved using the biphasic halogenative semi-pinacol reaction protocol. The resultant β-halo spiroketones, containing three contiguous stereogenic centers, were easily recovered with high diastereomeric and enantiomeric purities following conventional silica gel chromatography. The optically active products could be further manipulated chemically, affording synthetically interesting scaffolds with complete preservation of stereoisomeric integrity.

Enantioselective catalytic fluorinative aza-semipinacol rearrangement.

An efficient and highly stereoselective fluorinative aza-semipinacol rearrangement is described. The catalytic reaction requires use of Selectfluor in combination with the chiral, enantiopure phosphate anion derived from acid L3. Under optimized conditions, cyclopropylamines A were transformed into β-fluoro cyclobutylimines B in good yields and high levels of diastereo- and enantiocontrol.