Gold(II) Porphyrins in Photoinduced Electron Transfer Reactions

In the context of solar-to-chemical energy conversion, inspired by natural photosynthesis, the synthesis, electrochemical properties and photoinduced electron-transfer processes of three novel zinc(II)-gold(III) bis(porphyrin) dyads [Zn^II(P)–Au^III(P)]⁺ are presented (P: tetraaryl porphyrin). Time-resolved spectroscopic studies indicated ultrafast dynamics (k >10¹⁰ s⁻¹) after visible-light excitation, which finally yielded a charge-shifted state [Zn^II(P ^{⋅ +})–Au^II(P)]⁺ featuring a gold(II) center. The lifetime of this excited state is quite long due to a comparably slow charge recombination (k ≈3×10⁸ s⁻¹). The [Zn^II(P ^{⋅ +})–Au^II(P)]⁺ charge-shifted state is reductively quenched by amines in bimolecular reactions, yielding the neutral zinc(II)–gold(II) bis(porphyrin) Zn^II(P)–Au^II(P). The electronic nature of this key gold(II) intermediate, prepared by chemical or photochemical reduction, is elucidated by UV/Vis, X-band EPR, gold L₃-edge X-ray absorption near edge structure (XANES) and paramagnetic ¹H NMR spectroscopy as well as by quantum chemical calculations. Finally, the gold(II) site in Zn^II(P)–Au^II(P) is thermodynamically and kinetically competent to reduce an aryl azide to the corresponding aryl amine, paving the way to catalytic applications of gold(III) porphyrins in photoredox catalysis involving the gold(III/II) redox couple.     

Interpenetration of a 3D Icosahedral M@Ni12 (M=Al,Ga) Framework with Porphyrin‐Reminiscent Boron Layers in MNi9B8

Two ternary borides MNi₉B₈ (M=Al, Ga) were synthesized by thermal treatment of mixtures of the elements. Single‐crystal X‐ray diffraction data reveal AlNi₉B₈ and GaNi₉B₈ crystallizing in a new type of structure within the space group Cmcm and the lattice parameters a=7.0896(3) Å, b=8.1181(3) Å, c=10.6497(4) Å and a=7.0897(5) Å, b=8.1579(4) Å, c=10.6648(7) Å, respectively. The boron atoms build up two‐dimensional layers, which consist of puckered [B₁₆] rings with two tailing B atoms, whereas the M atoms reside in distorted vertices‐condensed [Ni₁₂] icosahedra, which form a three‐dimensional framework interpenetrated by boron porphyrin‐reminiscent layers. An unusual local arrangement resembling a giant metallo‐porphyrin entity is formed by the [B₁₆] rings, which, due to their large annular size of approximately 8 Å, chelate four of the twelve icosahedral Ni atoms. An analysis of the chemical bonding by means of the electron localizability approach reveals strong covalent B?B interactions and weak Ni?Ni interactions. Multi‐center dative B?Ni interaction occurs between the Al–Ni framework and the boron layers. In agreement with the chemical bonding analysis and band structure calculations, AlNi₉B₈ is a Pauli‐paramagnetic metal.     

Be3Ru: Polar Multiatomic Bonding in the Closest Packing of Atoms

The new phase Be₃Ru crystallizes with TiCu₃-type structure (space group Pmmn (59), a=3.7062(1) Å, b=4.5353(1) Å, c=4.4170(1) Å), a coloring variant of the hexagonal closest packing (hcp) of spheres. The electronic structure revealed that Be₃Ru has a pseudo-gap close to the Fermi level. A strong charge transfer from Be to Ru was observed from the analysis of electron density within the Quantum Theory of Atoms in Molecules (QTAIM) framework and polar three- and four-atomic Be−Ru bonds were observed from the ELI−D (electron localizability indicator) analysis. This situation is very similar to the recently investigated Be₅Pt and Be₂₁Pt₅ compounds. The unusual crystal chemical feature of Be₃Ru is that different charged species belong to the same closest packing, contrary to typical inorganic compounds, where the cationic components are located in the voids of the closest packing formed by anions. Be₃Ru is a diamagnet displaying metallic electrical resistivity.     

Understanding the European policy landscape and its impact on change in mathematics and science pedagogies

Effecting an increase in the use of inquiry-based learning pedagogies in mathematics and science at a large scale across Europe has been promoted within the European education policy space. The primary goal is greater numbers of young people having more positive dispositions towards future careers in science, engineering and technology (Rocard in EUR22845—science education now: a renewed pedagogy for the future of Europe, http://www.eesc.europa.eu/resources/docs/rapportrocardfinal.pdf, 2007). We report on policy research as part of a European funded project that aims to support professional development that might bring about such changes. Our analysis points to policy activity that, to a greater or lesser degree, appears to be ineffective in meeting the desired outcomes in respect of teacher change. We identify why, although there is much policy activity, initiatives struggle to make an impact on teaching practices and learners’ experiences. Overall we point to misalignment in what policy defines in terms of input to learning, what is measured and valued in terms of outcomes, and what is desired in the teaching process. We also point to how policy fails to support development of the individual teacher and the teaching profession as a whole in ways that might effect the desired change.     

Four novel spirooxazacamphorsultam derivatives

The chiral compounds (6aS,9S,10aR)‐11,11‐dimethyl‐5,5‐dioxo‐2,3,8,9‐tetrahydro‐6H‐6a,9‐methanooxazaolo[2,3‐i][2,1]benzisothiazol‐10(7H)‐one, C₁₂H₁₇NO₄S, (1), (7aS,10S,11aR)‐12,12‐dimethyl‐6,6‐dioxo‐3,4,9,10‐tetrahydro‐7H‐7a,10‐methano‐2H‐1,3‐oxazino[2,3‐i][2,1]benzisothiazol‐11(8H)‐one, C₁₃H₁₉NO₄S, (2), (6aS,9S,10R,10aR)‐11,11‐dimethyl‐5,5‐dioxo‐2,3,7,8,9,10‐hexahydro‐6H‐6a,9‐methanooxazolo[2,3‐i][2,1]benzisothiazol‐10‐ol, C₁₂H₁₉NO₄S, (3), and (7aS,10S,11R,11aR)‐12,12‐dimethyl‐6,6‐dioxo‐3,4,8,9,10,11‐hexahydro‐7H‐7a‐methano‐2H‐[1,3]oxazino[2,3‐i][2,1]benzisothiazol‐11‐ol, C₁₃H₂₁NO₄S, (4), consist of a camphor core with a five‐membered spirosultaoxazolidine or six‐membered spirosultaoxazine, as both their keto and hydroxy derivatives. In each structure, the molecules are linked via hydrogen bonding to the sulfonyl O atoms, forming chains in the unit‐cell b‐axis direction. The chains interconnect via weak C—H...O interactions. The keto compounds have very similar packing but represent the highest melting [507–508 K for (1)] and lowest melting [457–458 K for (2)] solids.     

Efficient enantioselective synthesis of condensed and aromatic-ring-substituted tyrosine derivatives

An efficient access to both condensed and conjugated tyrosine analogues of high enantiomeric purity is described. Novel ring-substituted tyrosines were synthesized by Suzuki cross couplings of appropriately protected l-3-iodotyrosine with a series of activated and deactivated boronic acid derivatives to achieve the target compounds in high yields. d- and l-4-hydroxy-1-naphthylalanines were readily prepared from the corresponding alpha-enamide in two different approaches, by asymmetric hydrogenation as well as by unselective hydrogenation and enzymatic resolution of the racemic mixture.     

A high-throughput screening assay for hydroxynitrile lyase activity

A high-throughput screening assay for hydroxynitrile lyase activity accepting a wide range of HNL-substrates is presented, which is useful either for enzyme fingerprinting or screening of huge variant libraries generated in metagenome or directed evolution approaches.