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- ItemShape-adaptive single-molecule magnetism and hysteresis up to 14 K in oxide clusterfullerenes Dy2O@C72 and Dy2O@C74 with fused pentagon pairs and flexible Dy-(μ2-O)-Dy angle(Cambridge : Royal Society of Chemistry, 2020) Velkos, G.; Yang, W.; Yao, Y.-R.; Sudarkova, S.M.; Liu, X.; Büchner, B.; Avdoshenko, S.M.; Chen, N.; Popov, A.A.Dysprosium oxide clusterfullerenes Dy2O@Cs(10528)-C72 and Dy2O@C2(13333)-C74 are synthesized and characterized by single-crystal X-ray diffraction. Carbon cages of both molecules feature two adjacent pentagon pairs. These pentalene units determine positions of endohedral Dy ions hence the shape of the Dy2O cluster, which is bent in Dy2O@C72 but linear in Dy2O@C74. Both compounds show slow relaxation of magnetization and magnetic hysteresis. Nearly complete cancelation of ferromagnetic dipolar and antiferromagnetic exchange Dy⋯Dy interactions leads to unusual magnetic properties. Dy2O@C74 exhibits zero-field quantum tunneling of magnetization and magnetic hysteresis up to 14 K, the highest temperature among Dy-clusterfullerenes.
- ItemDesign of a scalable AuNP catalyst system for plasmon-driven photocatalysis(Cambridge : Royal Society of Chemistry, 2018) Stolle, H.L.K.S.; Garwe, F.; Müller, R.; Krech, T.; Oberleiter, B.; Rainer, T.; Fritzsche, W.; Stolle, A.In this work we present a simple, fast and cost-efficient synthesis of a metal nanoparticle catalyst on a glass support for plasmon driven heterogeneous photocatalysis. It is based on efficient mixing of metal salts as particle precursors with porous glass as the supporting material in a mixer ball mill, and the subsequent realization of a complete catalyst system by laser sintering the obtained powder on a glass plate as the support. By this, we could obtain catalyst systems with a high particle proportion and an even spatial particle distribution in a rapid process, which could be applied to various kinds of metal salt resulting in plasmon active metal nanoparticles. Furthermore, the catalyst production process presented here is easily scalable to any size of area that is to be coated. Finally, we demonstrate the catalytic performance of our catalysts by a model reaction of ethanol degradation in a self-designed lab-scale reactor.
- ItemDirect chemical vapor deposition synthesis of large area single-layer brominated graphene(Cambridge : Royal Society of Chemistry, 2019) Hasan, M.; Meiou, W.; Yulian, L.; Ullah, S.; Ta, H.Q.; Zhao, L.; Mendes, R.G.; Malik, Z.P.; Ahmad, N.M.; Liu, Z.; Rümmeli, M.H.Graphene and its derivatives such as functionalized graphene are considered to hold significant promise in numerous applications. Within that context, halogen functionalization is exciting for radical and nucleophilic substitution reactions as well as for the grafting of organic moieties. Historically, the successful covalent doping of sp2 carbon with halogens, such as bromine, was demonstrated with carbon nanotubes. However, the direct synthesis of brominated graphene has thus far remained elusive. In this study we show how large area brominated graphene with C-Br bonds can be achieved directly (i.e. a single step) using hydrogen rich low pressure chemical vapor deposition. The direct synthesis of brominated graphene could lead to practical developments. © The Royal Society of Chemistry.
- ItemEngineering Kitaev exchange in stacked iridate layers: Impact of inter-layer species on in-plane magnetism(Cambridge : Royal Society of Chemistry, 2019) Yadav, R.; Eldeeb, M.S.; Ray, R.; Aswartham, S.; Sturza, M.I.; Nishimoto, S.; Van Den Brink, J.; Hozoi, L.Novel functionalities may be achieved in oxide electronics by appropriate stacking of planar oxide layers of different metallic species, MOp and M′Oq. The simplest mechanism allowing the tailoring of the electronic states and physical properties of such heterostructures is of electrostatic nature - charge imbalance between the M and M′ cations. Here we clarify the effect of interlayer electrostatics on the anisotropic Kitaev exchange in H3LiIr2O6, a recently proposed realization of the Kitaev spin liquid. By quantum chemical calculations, we show that the precise position of H+ cations between magnetically active [LiIr2O6]3- honeycomb-like layers has a strong impact on the magnitude of Kitaev interactions. In particular, it is found that stacking with straight interlayer O-H-O links is detrimental to in-plane Kitaev exchange since coordination by a single H-ion of the O ligand implies an axial Coulomb potential at the O site and unfavorable polarization of the O 2p orbitals mediating the Ir-Ir interactions. Our results therefore provide valuable guidelines for the rational design of Kitaev quantum magnets, indicating unprecedented Kitaev interactions of ≈40 meV if the linear interlayer linkage is removed.
- ItemExpansion of the (BB)Ru metallacycle with coinage metal cations: Formation of B-M-Ru-B (M = Cu, Ag, Au) dimetalacyclodiboryls(Cambridge : Royal Society of Chemistry, 2018) Eleazer, B.J.; Smith, M.D.; Popov, A.A.; Peryshkov, D.V.In this work, we introduce a novel approach for the selective assembly of heterometallic complexes by unprecedented coordination of coinage metal cations to strained single ruthenium-boron bonds on a surface of icosahedral boron clusters. M(i) cations (M = Cu, Ag, and Au) insert into B-Ru bonds of the (BB)-carboryne complex of ruthenium with the formation of four-membered B-M-Ru-B metalacycles. Results of theoretical calculations suggest that bonding within these metalacycles can be best described as unusual three-center-two-electron B-M⋯Ru interactions that are isolobal to B-H⋯Ru borane coordination for M = Cu and Ag, or the pairs of two-center-two electron B-Au and Au-Ru interactions for M = Au. These transformations comprise the first synthetic route to exohedral coinage metal boryl complexes of icosahedral closo-{C2B10} clusters, which feature short Cu-B (2.029(2) Å) and Ag-B (2.182(3) Å) bonds and the shortest Au-B bond (2.027(2) Å) reported to date. The reported heterometallic complexes contain Cu(i) and Au(i) centers in uncharacteristic square-planar coordination environments. These findings pave the way to rational construction of a broader class of multimetallic architectures featuring M-B bonds.