Reactivity of a N-heterocyclic carbene, 1,3-di-(1-adamantyl) imidazol-2-ylidene, with a pseudo-acid: structural characterization of Claisen condensation adduct

The reactivity of a N-heterocyclic carbene (NHC) with a pseudo-acid (ester in this case) is described. The product results from an unusual C-H bond activation. The structure of the product has been established by a single crystal diffraction study.     

Characterization of aliphatic and aromatic polyester hyperbranched dendrimers by AFM imaging

The aggregates of aliphatic (AL-PE) and aromatic polyester (AR-PE) hyperbranched dendrimers were imaged by tapping mode atomic force microscopy (AFM). The second and third generations of AL-PE dendrimers were adsorbed on mica in large aggregates of 150- and 166-nm diameters with little heights (ca. 1–2 nm). The origin of such flattened aggregates is attributed to their favorable adsorption on mica in view of the presence of –OH surface groups. AR-PE did not show such flattened aggregates instead small aggregates of 63 nm were observed in an organized manner beaving a cavity in the center of each aggregate. The organized aggregates of AR-PE with smaller dimension than AL-PE are ascribed to less favorable adsorption of the latter on mica in view of its stronger hydrophobicity.     

Synthesis,spectroscopy and cyclic voltammetry of cobalt(III) complexes with 5-methyl-3-formylpyrazole N(4)-cyclohexylthiosemicarbazone (HMPz4Cy): X-ray crystal structure of [Co(MPz4Cy)2]Cl · 2.75H2O

The coordination behaviour of the novel ligand, HMPz4Cy, is reported, together with solid state isolation of its diamagnetic cobalt(III) complexes, [Co(MPz4Cy)₂]X · nH₂O (X = Cl, Br, NO₃, ClO₄ and BF₄). I.r. and ¹H-n.m.r. data for the free ligand and its Co^III complexes confirm that the ligand, HMPz4Cy, acts as a uninegative anion with NNS tridentate function via the pyrazolyl nitrogen (tertiary), azomethine nitrogen and thiol sulphur. Electronic spectra (both solid and solution) are commensurate with a distorted octahedral environment for the reported Co^III species. Cyclic voltammograms of Co^III complexes indicate a quasireversible Co⁺³/Co⁺² couple. X-ray crystallography of a representative species, [Co(MPz4Cy)₂]Cl · 2.75H₂O (C2, monoclinic), has shown unambiguously that the two ligands are orthogonally coordinated to the central Co^III ion with both the thiolato sulphurs and both pyrazolyl nitrogen atoms in cis positions.     

Effect of nano-size fumed silica on ionic conductivity of PVdF-HFP-based plasticized nano-composite polymer electrolytes

Nano-composite polymer electrolytes containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), ammonium tetrafluoroborate (NH₄BF₄), and nano-size fumed silica (SiO₂) have been prepared and characterized by complex impedance spectroscopy. Ionic conductivity of polymer has been found to increase with the addition of NH₄BF₄, and a maximum conductivity of 3.62 × 10^?6 S/cm has been obtained at 30 wt% NH₄BF₄. The formation of ion aggregates at high concentration of salt has been explained by Bjerrum’s law and mass action considerations. The conductivity of polymer electrolytes has been increased by three orders of magnitude (10^?6 to 10^?3 S/cm) with the addition of plasticizer, and a maximum conductivity of 1.10 × 10^?3 S/cm has been observed at 80 wt% DMA. An increase in conductivity with the addition of nano-size fumed silica is attributed due to the formation of space-charge layers. A maximum conductivity of 7.20 × 10^?3 S/cm has been observed for plasticized nano-composite polymer electrolytes at 3 wt% SiO₂. X-ray diffraction analysis of polymer electrolyte system was also carried out. A small change in conductivity of nano-composite polymer electrolytes observed over the 30–130 °C temperature range and for a period of 30 days is also desirable for their use in various applications.     

New pimarane diterpenes and other antimycobacterial metabolites from Anisochilus verticillatus

Phytochemical investigation of the acetone extract of the aerial parts of Anisochilus verticillatus afforded a new 8,9-secopimarane diterpene (1), two new isopimarane diterpenes (2, 3) and the known ursolic acid (4), α-amyrin (5), β-amyrin (6), stigmast-5-en-3-one (7) and hydroxychavicol (8). Structures of the new compounds were elucidated with the help of 1D and 2D nuclear magnetic resonance spectroscopic data, and single crystal X-ray crystallography of compound 3. Compounds 2 and 8 inhibited Mycobacterium tuberculosis H37Ra with an IC₅₀ of 11.3 (IC₉₀ of 20.0 μg/mL) and 12.5 μg/mL, respectively. Correspondingly, molecular docking studies with Extra Precision Glide revealed a correlation between score and biological activity for these compounds to describe the molecular basis for the most significant SAR results.     

Polymeric Nanoparticles Amenable to Simultaneous Installation of Exterior Targeting and Interior Therapeutic Proteins

Effective delivery of therapeutic proteins is a formidable challenge. Herein, using a unique polymer family with a wide‐ranging set of cationic and hydrophobic features, we developed a novel nanoparticle (NP) platform capable of installing protein ligands on the particle surface and simultaneously carrying therapeutic proteins inside by a self‐assembly procedure. The loaded therapeutic proteins (e.g., insulin) within the NPs exhibited sustained and tunable release, while the surface‐coated protein ligands (e.g., transferrin) were demonstrated to alter the NP cellular behaviors. In vivo results revealed that the transferrin‐coated NPs can effectively be transported across the intestinal epithelium for oral insulin delivery, leading to a notable hypoglycemic response.     

Morphology-controlled assembly of ZnO nanostructures: a bioinspired method and visible luminescence

In a bioinspired methodology, positively charged polypeptides and polyamines directly catalyse ZnO mineralization under "green" conditions of room temperature and neutral pH. The polyamines not only act as mineralizing agents for the formation of ZnO nanoparticles, but also self-assemble the nanoparticles to form spindle-like morphologies at these very ambient conditions. Both the directional growth of ZnO and its luminescent property have a pH dependency. At higher pH, the ZnO shape changes to a rodlike morphology that exhibits green photoluminescence with different intensity than that for ZnO spindles.     

Isotopic dependence of fusion probabilities for neutron-deficient and -rich colliding nuclei

Isotopic dependence of the fusion dynamics is studied by analyzing the collision of a large number of isotopes of Ca and Ni with 0.6 N/Z 2. This study, which results from the Skyrme energy density formalism, reveals that the addition of neutrons favors fusion of reacting partners, whereas the reverse happens with the removal of neutrons. The fusion barrier heights and positions follow a non-linear second-order dependence on ( -1 ), whereas fusion cross-sections can be parameterized by a straight line.-1     

ESR and NMR studies of poly (amidoamine) dendrimers with ionic surfactants in different media

The electron paramagnetic resonance (EPR) study has been carried out for the micellar solutions of various ionic surfactant solutions as well as various generations of aqueous dendrimer both in their respective presence as well as their absence at 25°C and in different media. From these measurements, the rotation correlation time (τ_B) have been calculated for all the ionic surfactant + PAMAM + water system. A variation in the τ_Bvalue remains mostly constant for the dodecyltrimethyammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB) + PAMAM + water ternary mixtures. The τ_Bvalue shows an increase with the increase in the amount of PAMAM for SDS in basic medium and for 12-2-12 in acidic medium. It has been concluded from these results that SDS undergo complexation with all generations of PAMAM in basic medium and 12-2-12 in acidic medium and produce stronger hydrophobic environment. The nuclear magnetic resonance study (NMR) allowed us to evaluate the spin–spin relaxation (T₁) times of SDS in the presence of all generations of PAMAM. The T₁ values for all the tail protons of SDS showed a slight decrease with the increase in the constant amount of PAMAM suggesting the adsorption of PAMAM molecules on the micelle surface.     

Synthesis of phosphorus esters by transesterification mediated by N-heterocyclic carbenes (NHCs)

The versatile nucleophilic organic catalysts N-heterocyclic carbenes (NHCs) have been shown to effectively mediate the transesterification of phosphorus esters under mild conditions; user-friendly imidazolium salts can also be employed as pre-catalysts.