Formation of internally nanostructured triblock copolymer particles

Particles with an internal structure have been found in dilute water solutions of a triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), which has short hydrophilic PEO endblocks compared to the central hydrophobic PPO block (EO5PO68EO5, L121). The properties of the block copolymer particles (i.e., their structure, size, and time stability) have been investigated using cryogenic transmission electron microscopy (cryo-TEM) in combination with dynamic light scattering (DLS) and turbidity measurements. The particles were formed in dilute solutions by quenching the temperature to temperatures where the reversed hexagonal phase is in equilibrium with a solution of unaggregated L121 copolymers (L1). From the DLS measurements, a mean hydrodynamic radius of 158 nm was extracted. The time-scan turbidity measurements were found to be unchanged for about 46 h. At higher copolymer concentrations, a reversed hexagonal phase (H2) exists in the L121/water system. SAXS was used to investigate the internal structure of the dispersed L121-based particles containing 15 wt % L121. It was found that the internal structure transforms from H2 to an inverse micellar system (L2) as the temperature increases from 37 to 70 degrees C.     

The performance of density functional theory for LnF (Ln=Nd,Eu, Gd,Yb) and YbH

Different density functional theory (DFT) functionals have been evaluated by studying geometries and bond strengths of YbH, YbF, EuF, GdF, and NdF and compared with accurate CCSD(T) results and, when available, experiment. The agreement between the CCSD(T) results and experiment, when available, is good. The agreement is also good between bond strengths calculated at the DFT level using relativistic effective core potentials and the CCSD(T) results. However, the all-electron ADF calculations systematically overestimate binding energies. The geometries obtained by both the all-electron and the effective-core-potential-based DFT calculations are generally in good agreement with the CCSD(T) results.Contribution to the Björn Roos Honorary Issue     

Reactions of Group 8, 9, and 10 monocations (Fe+, Co+, Ni+, Ru+, Rh+, Pd+, Os+, Ir+, Pt+) with phosphane in the gas phase

The reactions of Group 8, 9 and 10 monocations with phosphane were studied under single-collision conditions in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Fe(+) is completely unreactive, Co(+) reacts slowly and shows both adduct formation and P-H bond activation, and Ni(+) reacts slowly as well but shows adduct formation only. In contrast to their first-row congeners, the investigated second- and third-row transition metal monocations show facile P-H bond activations. Remarkably, extensive dehydrogenations of the collision complexes yield cations MPH(+), MP(2) (+), MP(3)H(+), MP(4) (+) and so on. Exceptional behaviour is shown by the two d(9) cations palladium (whose "dehydrogenation power" is rather limited) and platinum (which gives rise to a great manifold of only partially dehydrogenated species as well). Collision-induced dissociation experiments suggest that P(2) and PH units are formed as ligands.     

Synthesis and conformational analysis of 9,10-bis-aminomethyl-11,12-dicarboxy-dibenzobarrelene derivatives

The synthesis of bis-γ-amino acid dibenzobarrelene derivatives (9,10-bis-aminomethyl-11,12-bis-carboxy-dibenzobarrelene) is presented. Bromomethylation of anthracene followed by azide substitution gave 9,10-bis-azidomethylanthracene. Azide reduction, N-Boc protection, and Diels-Alder cycloaddition in DMAD furnished the protected 9,10-bi-aminomethyl-11,12-dicarboxy-dibenzobarrelene derivative, which was further converted into the bis-γ-amino acid methyl ester, the N-Boc-protected bis-γ-amino methyl amide, and a bis-γ-lactam. Monte Carlo simulations and X-ray analysis of the 9,10-substituted dibenzobarrelenes revealed an exposed hydrophobic surface surrounded by amino and carboxy groups.     

Locoselective [4 + 2] Cycloadditions of Vinylindoles with Inverse Electron Demand: A new access of indolyl-substituted and annellated pyridazines

2-Vinylindole ( 1a ) and its donor- and acceptor-substituted (E)-derivatives 1b – e react highly locoselectively with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate ( 3 ) to form the novel (indol-2-yl)-1,4-dihydropyridazines 4a and 7 as well as the heterocyclic annellated pyridazines 4b , 5 , and 6 . The reactions of the structurally related 3-vinylindoles 2a – e with 3 also gave rise to new indol-3-ylpyridazines 8 , 9 , and 10 . The locoselectivities of these Diels-Alder reactions were controlled mainly by steric effects.     

Mehrkernige Kobaltkomplexe. IV. Darstellung und Struktur von [(papd)Co(O2)Co(papd)](S2O6)(NO3)2 · 4 H2O1)

Polynuclear Cobalt Complexes. IV. Preparation and Structure of [(papd)Co(O₂)Co(papd)](S₂O₆)(NO₃)₂ · 4 H₂O The binuclear peroxo complex [(papd)Co(O₂)Co(papd)](S₂O₆)(NO₃)₂ · 4 H₂O I crystallizes in the triclinic space group P1 . Lattice constants are a = 9.405(4), b = 9.270(4), c = 12.218(6)Å, α = 89.58(5), β = 99.08(6), γ = 114.79(5)° for Z = 1. The binuclear cation has a center of symmetry, so the Co? O? O? Co unit is planar. Three chelate rings have a common plane, the ligand configuration is δ.     

Oxidative Transformations of Organic Compounds Mediated by Redox Molecular Sieves

Zeolites are viewed by some as the “philosopher's stone” of modern chemistry.^[1] They are more or less indispensable in oil refining and petrochemicals manufacture where they are widely applied as solid acid catalysts. More recently attention has been focused on their use in the manufacture of fine chemicals. The synthetic utility of zeolites and related molecular sieves (zeotypes) has been considerably extended by the incorporation of redox metals into their frameworks. The resulting redox molecular sieves catalyze a variety of selective oxidations under mild conditions in the liquid phase. Their structural diversity–including variation of the redox metal, incorporation of metal complexes, and the size and polarity of the micropores–provides the possibility of designing tailor-made solid catalysts (“mineral enzymes”) for liquid-phase oxidations with clean oxidants such as O₂, H₂O₂, and RO₂H. Hence, they have enormous potential in industrial organic synthesis as environmentally friendly alternatives to traditional oxidations employing inorganic oxidants in stoichiometric amounts. A primary aim of this review is to familiarize organic chemists with the synthetic potential of redox molecular sieves. An outline of their synthesis, structures, and chemical properties, highlighting their unique advantages, is followed by a discussion of general (mechanistic) features that influence the choice of a suitable catalyst for a particular type of oxidation. The main part of the review deals with the oxidation of various substrates of synthetic interest–such as alkanes, alkenes, (alkyl)arenes, alcohols, and amines–and emphasizes the advantages of redox molecular sieves (including selectivity and stability) over their homogeneous counterparts. New directions towards truly biomimetic solid catalysts, for example zeolite-encapsulated chiral metal complexes as heterogeneous catalysts for asymmetric oxidations, are high-lighted.     

Charge carrier governed temperature dependence of the electric field gradient for111Cd in tellurium

Using the TDPAC-method with the proble nucleus¹¹¹Cd the electric quadrupole interaction (QI) in the trigonal semiconductor Te has been investigated in the temperature range 77 KT655 K. In contrast to most metals the quadrupole frequencyv _Q increases with increasing temperature. This is a consequence of the fact that in metals the charge carrier density is temperature independent, whereas in semiconductors it strongly increases with temperature. A comparison between the temperature variation of the quadrupole coupling constantv _Q and that of the charge carrier density leads to the conclusion that the QI in Te is governed by changes in the free electron density.