Dual Electroactivity in a Covalent Organic Network with Mechanically Interlocked Pillar[5]arenes

The synthesis and characterization of a polyrotaxanated covalent organic network (CON) based on the association between the viologen and pillar[5]arene (P[5]OH) units are reported. The mechanical bond allows for the irreversible insertion of n-type redox centers (P[5]OH macrocycles) within a pristine structure based on p-type viologen redox centers. Both redox units are active on a narrow potential range and, in water, the presence of P[5]OH greatly increases the electroactivity of the material.     

A phase field approach for multivariant martensitic transformations of stable and metastable phases

A phase field model approach for multivariant martensitic transformations of stable and metastable phases is introduced. The evolution of the microstructure is examined with respect to elastic energy minimization in which one or two martensitic orientation variants are considered. In this context, the martensitic nucleation behavior is simulated for different activation barriers. Furthermore, the influence of time-dependent external loads on the formation of the different phases is studied. The numerical implementation is performed with finite elements and an implicit time integration scheme.     

Asymmetric hydrogenation of trisubstituted N-acetyl enamides derived from 2-tetralones using ruthenium-SYNPHOS catalysts: a practical synthetic approach to the preparation of β3-adrenergic agonist SR58611A

The asymmetric hydrogenation of various trisubstituted enamides derived from 2-tetralones under mild reaction conditions using Ru-SYNPHOS catalysts is reported. This practical and clean method gives access to several chiral 2-aminotetralins derivatives in high isolated yields and enantiomeric excesses up to 95% depending on the substitution pattern of the aromatic ring and the nature of the amide moiety. In addition, the usefulness of the current method is demonstrated via a practical synthetic approach to the enantiomerically pure SR58611A compound, a potent and selective β₃-adrenergic receptor agonist.     

Directed Assembly of Soft Anisotropic Nanoparticles by Colloid Electrospinning

Directed assembly of triblock copolymer worms to produce nanostructured fibers is achieved via colloid electrospinning. These copolymer worms are conveniently prepared by polymerization‐induced self‐assembly in concentrated aqueous dispersion. Addition of a second water‐soluble component, poly(vinyl alcohol), is found to be critical for the production of well‐defined fibers: trial experiments performed using the worms alone produce only spherical microparticles. Transmission electron microscopy studies confirm that the worm morphology survives electrospinning and the worms become orientated parallel to the main axis of the fibers during their generation. The average deviant angle (θ_dev) between the worm orientation and fiber axis decreases from 17° to 9° as the worm/PVA mass ratio increases from 1.15:1 to 5:1, indicating a greater degree of worm alignment within fibers with higher worm contents and smaller fiber diameters. Thus triblock copolymer fibers of ≈300 ± 120 nm diameter can be readily produced that comprise aligned worms on the nanoscale.

     

Encapsulation of phthalocyanine supramolecular stacks into virus-like particles

We report herein the encapsulation of a water-soluble phthalocyanine (Pc) into virus-like particles (VLPs) of two different sizes, depending on the conditions. At neutral pH, the cooperative encapsulation/templated assembly of the particles induces the formation of Pc stacks instead of Pc dimers, due to an increased confinement concentration. The Pc-containing VLPs may potentially be used as photosensitizer/vehicle systems for biomedical applications such as photodynamic therapy.     

Syntheses, crystal structures, reactivity, and photochemistry of gold(III) bromides bearing N-heterocyclic carbenes

Gold(I) complexes bearing N-heterocyclic carbenes (NHC) of the type (NHC)AuBr (3a/3b) [NHC = 1-methyl-3-benzylimidazol-2-ylidene (= MeBnIm), and 1,3-dibenzylimidazol-2-ylidene (= Bn(2)Im)] are prepared by transmetallation reactions of (tht)AuBr (tht = tetrahydrothiophene) and (NHC)AgBr (2a/2b). The homoleptic, ionic complexes [(NHC)(2)Au]Br (6a/6b) are synthesized by the reaction with free carbene. Successive oxidation of 3a/3b and 6a/6b with bromine gave the respective (NHC)AuBr(3) (4a/4b) and [(NHC)(2)AuBr(2)]Br (7a/7b) in good overall yields as yellow powders. All complexes were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. Reactions of the Au(III) complexes towards anionic ligands like carboxylates, phenolates and thiophenolates were investigated and result in a complete or partial reduction to a Au(I) complex. Irradiation of the Au(III) complexes with UV light yield the Au(I) congeners in a clean photo-reaction.     

Determination of the binding sites for oxaliplatin on insulin using mass spectrometry-based approaches

Using insulin as a model protein for binding of oxaliplatin to proteins, various mass spectrometric approaches and techniques were compared. Several different platinum adducts were observed, e.g. addition of one or two diaminocyclohexane platinum(II) (Pt(dach)) molecules. By top-down analysis and fragmentation of the intact insulin–oxaliplatin adduct using nano-electrospray ionisation quadrupole time-of-flight mass spectrometry (nESI-Q-ToF-MS), the major binding site was assigned to histidine5 on the insulin B chain. In order to simplify the interpretation of the mass spectrum, the disulphide bridges were reduced. This led to the additional identification of cysteine6 on the A chain as a binding site along with histidine5 on the B chain. Digestion of insulin–oxaliplatin with endoproteinase Glu-C (GluC) followed by reduction led to the formation of five peptides with Pt(dach) attached. Identification of several of the binding sites was obtained using matrix-assisted laser desorption/ionization (MALDI)-ToF-ToF-MS and liquid chromatography-nESI-Q-ToF-MS. Upon comparing the top-down and bottom-up approaches, the suitability of the bottom-up approach for determining binding sites was questioned, as the release and possible re-association of Pt(dach) were demonstrated upon enzymatic digestion. The associated advantages and disadvantages of ESI and MALDI were also pointed out.