Concentration of sodium ion as the determining factor for the association of dansyl amino acids with the teicoplanin molecule in reversed-phase liquid chromatography

The mechanism of the binding of D,L dansyl amino acids to teicoplanin was investigated. Na+ was used as an indicator of the interactions between the solutes and teicoplanin. The number (n) of sodium ions, Na+, excluded from the solute-teicoplanin interface when analyte transfer occurred was determined. A thermodynamic study and enthalpy-entropy compensation were performed to further explore the interaction mechanism. From these results, it was shown that teicoplanin was balanced between 2 conformational states characterized by distinct enantioselective properties. This approach indicates that liquid chromatography (LC) is a useful tool to extract physicochemical and molecular information from retention data. Thus, LC can be used as a complementary technique with the conventional techniques of molecular interaction analysis.     

Investigation of the interface in silica-encapsulated liposomes by combining solid state NMR and first principles calculations

In the context of nanomedicine, liposils (liposomes and silica) have a strong potential for drug storage and release schemes: such materials combine the intrinsic properties of liposome (encapsulation) and silica (increased rigidity, protective coating, pH degradability). In this work, an original approach combining solid state NMR, molecular dynamics, first principles geometry optimization, and NMR parameters calculation allows the building of a precise representation of the organic/inorganic interface in liposils. {(1)H-(29)Si}(1)H and {(1)H-(31)P}(1)H Double Cross-Polarization (CP) MAS NMR experiments were implemented in order to explore the proton chemical environments around the silica and the phospholipids, respectively. Using VASP (Vienna Ab Initio Simulation Package), DFT calculations including molecular dynamics, and geometry optimization lead to the determination of energetically favorable configurations of a DPPC (dipalmitoylphosphatidylcholine) headgroup adsorbed onto a hydroxylated silica surface that corresponds to a realistic model of an amorphous silica slab. These data combined with first principles NMR parameters calculations by GIPAW (Gauge Included Projected Augmented Wave) show that the phosphate moieties are not directly interacting with silanols. The stabilization of the interface is achieved through the presence of water molecules located in-between the head groups of the phospholipids and the silica surface forming an interfacial H-bonded water layer. A detailed study of the (31)P chemical shift anisotropy (CSA) parameters allows us to interpret the local dynamics of DPPC in liposils. Finally, the VASP/solid state NMR/GIPAW combined approach can be extended to a large variety of organic-inorganic hybrid interfaces.     

Rhodium(II) carbene-mediated modification of 2-deoxystreptamine surrogates

Rhodium(II)-catalyzed decomposition of carbene precursors grafted to the alcohol of diaminocyclopentanols promotes clean formation of a C-N bond via 1,6-insertion into an adjacent carbamate or azide. These modifications of 2-deoxystreptamine surrogates might give rise to aminoglycoside mimics where the two nitrogen atoms will be differentiated.     

Dearomatization of 3-Nitroindoles with Highly γ-Functionalized Allenoates in Formal (3+2) Cycloadditions

3-Nitroindoles are easily reacted with highly substituted γ-allenoates in the presence of a commercially available phosphine catalyst. For instance, allenoates derived from biomolecules such as amino and deoxycholic acids are combined for the first time with 3-nitroindole. The corresponding dearomatized (3+2) tricyclic cycloadducts are obtained as α-regioisomers exclusively. DFT computations shed light on this multi-step reaction mechanism and on the selectivities observed in the sequence.     

Star-Shaped Ruthenium Complexes as Prototypes of Molecular Gears

The design and synthesis of two families of molecular-gear prototypes is reported, with the aim of assembling them into trains of gears on a surface and ultimately achieving controlled intermolecular gearing motion. These piano-stool ruthenium complexes incorporate a hydrotris(indazolyl)borate moiety as tripodal rotation axle and a pentaarylcyclopentadienyl ligand as star-shaped cogwheel, equipped with five teeth ranging from pseudo-1D aryl groups to large planar 2D paddles. A divergent synthetic approach was followed, starting from a pentakis(p-bromophenyl)cyclopentadienyl ruthenium(II) complex as key precursor or from its iodinated counterpart, obtained by copper-catalyzed aromatic Br/I exchange. Subsequent fivefold cross-coupling reactions with various partners allowed high structural diversity to be reached and yielded molecular-gear prototypes with aryl-, carbazole-, BODIPY- and porphyrin-derived teeth of increasing size and length.     

Guest‐Assisted Proton Conduction in the Sulfonic Mesoporous MIL‐101 MOF

Post‐synthesis modification of MIL‐101(Cr)‐NO₂ was explored in order to decorate the organic backbone by propyl‐sulfonic groups, with the aim to incorporate mobile and acidic protons for solid‐state proton electrolyte applications. The resulting solid switched from insulating towards proton superconductive behavior under humidity, while the conductivity recorded at 363 K and 95 % relative humidity reached 4.8×10^?3 S cm^?1. Propitiously, the impregnation of the material by strong acidic molecules (H₂SO₄) further boosted the proton conductivity performances up to the remarkable σ value of 1.3×10^?1 S cm^?1 at 363 K/95 % RH, which reaches the performances of the best proton conductive MOF reported so far.     

A General and Air‐tolerant Strategy to Conjugated Polymers within Seconds under Palladium(I) Dimer Catalysis

While current M⁰/M^II based polymerization strategies largely focus on fine‐tuning the catalyst, reagents and conditions for each and every monomer, this report discloses a single method that allows access to a variety of different conjugated polymers within seconds at room temperature. Key to this privileged reactivity is an air‐ and moisture stable dinuclear Pd^I catalyst. The method is operationally simple, robust and tolerant to air.     

Open source capillary electrophoresis

Open source paradigm is becoming widely accepted in scientific communities and open source hardware is finding its steady place in chemistry research. In this review article, we provide the reader with the most up‐to‐date information on open source hardware and software resources enabling the construction and utilization of an “open source capillary electrophoresis instrument”. While CE is still underused as a separation technique, it offers unique flexibility, low‐cost, and high efficiency and is particularly suitable for open source instrumental development. We overview the major parts of CE instruments, such as high voltage power supplies, detectors, data acquisition systems, and CE software resources with emphasis on availability of the open source information on the web and in the scientific literature. This review is the first of its kind, revealing accessible blueprints of most parts from which a fully functional open source CE system can be built. By collecting the extensive information on open source capillary electrophoresis in this review article, the authors aim at facilitating the dissemination of knowledge on CE within and outside the scientific community, fosters innovation and inspire other researchers to improve the shared CE blueprints.     

Transition‐Metal‐Free Acceptorless Decarbonylation of Formic Acid Enabled by a Liquid Chemical‐Looping Strategy

The selective decarbonylation of formic acid was achieved under transition‐metal‐free conditions. Using a liquid chemical‐looping strategy, the thermodynamically favored dehydrogenation of formic acid was shut down, yielding a pure stream of CO with no H₂ or CO₂ contamination. The transformation involves a two‐step sequence where methanol is used as a recyclable looping agent to yield methylformate, which is subsequently decomposed to carbon monoxide using alkoxides as catalysts.