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- ItemCrystal structure of diethyl (E)-2-[(benzofuran-2-yl)methylidene]succinate(Chester : International Union of Crystallography, 2015) Schirmer, Marie-Luis; Spannenberg, Anke; Werner, ThomasThe title compound, C17H18O5, was synthesized by a base-free catalytic Wittig reaction. The molecule consists of a diethyl itaconate unit, which is connected via the C=C double bond to a benzofuran moiety. The benzofuran ring system (r.m.s. deviation = 0.007 Å) forms dihedral angles of 79.58 (4) and 12.12 (10)° with the mean planes through the cis and trans ethoxycarbonyl groups, respectively. An intramolecular C-H...O hydrogen bond involving the O atom of the benzofuran moiety is observed. In the crystal, molecules are linked into ribbons running parallel to the b axis by C-H...O hydrogen bonds.
- ItemCrystal structure of bis{μ2-[(2-iminocyclopentylidene)methylidene]azanido-κ2 N:N'}bis[(η5-pentamethylcyclopentadienyl)zirconium(IV)] hexane monosolvate(Chester : International Union of Crystallography, 2015) Becker, Lisanne; Spannenberg, Anke; Arndt, Perdita; Rosenthal, UweThe title compound, [Zr2(C10H15)4(C6H6N2)2]·C6H14, was obtained by the stoichiometric reaction of adiponitrile with [Zr(C10H15)2([eta]2-Me3SiC2SiMe3)]. Intramolecular nitrile-nitrile couplings and deprotonation of the substrate produced the (1-imino-2-enimino)cyclopentane ligand, which functions as a five-membered bridge between the two metal atoms. The ZrIV atom exhibits a distorted tetrahedral coordination sphere defined by two pentamethylcyclopentadienyl ligands, by the imino unit of one (1-imino-2-enimino)cyclopentane and by the enimino unit of the second (1-imino-2-enimino)cyclopentane. The cyclopentane ring of the ligand shows an envelope conformation. The asymmetric unit contains one half of the complex and one half of the hexane solvent molecule, both being completed by the application of inversion symmetry. One of the pentamethylcyclopentadienyl ligands is disordered over two sets of sites with a refined occupancy ratio of 0.8111 (3):0.189 (3). In the crystal, the complex molecules are packed into rods extending along [100], with the solvent molecules located in between. The rods are arranged in a distorted hexagonal packing.
- ItemCrystal structure of (E)-dodec-2-enoic acid(Chester : International Union of Crystallography, 2015) Sonneck, Marcel; Peppel, Tim; Spannenberg, Anke; Wohlrab, SebastianThe crystal structure of (E)-dodec-2-enoic acid, C12H22O2, an [alpha],[beta]-unsaturated carboxylic acid with a melting point (295 K) near room temperature, is characterized by carboxylic acid inversion dimers linked by pairs of O-H...O hydrogen bonds. The carboxylic acid group and the following three carbon atoms of the chain of the (E)-dodec-2-enoic acid molecule lie almost in one plane (r.m.s. deviation for the four C atoms and two O atoms = 0.012 Å), whereas the remaining carbon atoms of the hydrocarbon chain adopt a nearly fully staggered conformation [moduli of torsion angles vary from 174.01 (13) to 179.97 (13)°].
- ItemCrystal structure of (E)-undec-2-enoic acid(Chester : International Union of Crystallography, 2015) Sonneck, Marcel; Peppel, Tim; Spannenberg, Anke; Wohlrab, SebastianIn the molecule of the title low-melting [alpha],[beta]-unsaturated carboxylic acid, C11H20O2, the least-squares mean line through the octyl chain forms an angle of 60.10 (13)° with the normal to plane of the acrylic acid fragment (r.m.s. deviation = 0.008 Å). In the crystal, centrosymmetrically related molecules are linked by pairs of O-H...O hydrogen bonds into dimers, forming layers parallel to the (041) plane.
- ItemCrystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand(Chester : International Union of Crystallography, 2016) Kessler, Monty; Godemann, Christian; Spannenberg, Anke; Beweries, TorstenThe crystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand are reported, namely [di-methylbis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κ2O,O')titanium(III) toluene monosolvate, [Ti(CF3O3S)(C20H30Si)]·C7H8, 1, and chlorido-[di-methyl-bis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κO)titanium(IV), [Ti(CF3O3S)(C20H30Si)Cl], 2. Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetra-hedral geometry, with the tri-fluoro-methane-sulfonate anion acting as a bidentate or monodentate ligand in 1 and 2, respectively. In 1, weak π-π stacking inter-actions involving the toluene solvent mol-ecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed.
- ItemCrystal structure of di-n-butylbis([eta]5-pentamethylcyclopentadienyl)hafnium(IV)(Chester : International Union of Crystallography, 2015) Arndt, Perdita; Schubert,Kathleen; Burlakov, Vladimir V.; Spannenberg, Anke; Rosenthal, UweThe crystal structure of the title compound, [Hf(C10H15)2(C4H9)2], reveals two independent molecules in the asymmetric unit. The diffraction experiment was performed with a racemically twinned crystal showing a 0.529 (5):0.471 (5) component ratio. Each HfIV atom is coordinated by two pentamethylcyclopentadienyl and two n-butyl ligands in a distorted tetrahedral geometry, with the cyclopentadienyl rings inclined to one another by 45.11 (15) and 45.37 (16)°. In contrast to the isostructural di(n-butyl)bis([eta]5-pentamethylcyclopentadienyl)zirconium(IV) complex with a noticeable difference in the Zr-butyl bonding, the Hf-Cbutyl bond lengths differ from each other by no more than 0.039 (3) Å.
- ItemStrong out-of-plane magnetic anisotropy in ion irradiated anatase TiO2 thin films(New York, NY : American Inst. of Physics, 2016) Stiller, M.; Barzola-Quiquia, J.; Esquinazi, P.; Spemann, D.; Meijer, J.; Lorenz, M.; Grundmann, M.The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.
- ItemDistribution of Cracks in a Chain of Atoms at Low Temperature(Cham (ZG) : Springer International Publishing AG, 2021) Jansen, Sabine; König, Wolfgang; Schmidt, Bernd; Theil, FlorianWe consider a one-dimensional classical many-body system with interaction potential of Lennard–Jones type in the thermodynamic limit at low temperature 1/β∈(0,∞). The ground state is a periodic lattice. We show that when the density is strictly smaller than the density of the ground state lattice, the system with N particles fills space by alternating approximately crystalline domains (clusters) with empty domains (voids) due to cracked bonds. The number of domains is of the order of Nexp(−βesurf/2) with esurf>0 a surface energy. For the proof, the system is mapped to an effective model, which is a low-density lattice gas of defects. The results require conditions on the interactions between defects. We succeed in verifying these conditions for next-nearest neighbor interactions, applying recently derived uniform estimates of correlations.
- ItemActively Tunable Collective Localized Surface Plasmons by Responsive Hydrogel Membrane(Weinheim : Wiley-VCH, 2019) Quilis, Nestor Gisbert; van Dongen, Marcel; Venugopalan, Priyamvada; Kotlarek, Daria; Petri, Christian; Cencerrado, Alberto Moreno; Stanescu, Sorin; Herrera, Jose Luis Toca; Jonas, Ulrich; Möller, Martin; Mourran, Ahmed; Dostalek, JakubCollective (lattice) localized surface plasmons (cLSP) with actively tunable and extremely narrow spectral characteristics are reported. They are supported by periodic arrays of gold nanoparticles attached to a stimuli-responsive hydrogel membrane, which can on demand swell and collapse to reversibly modulate arrays period and surrounding refractive index. In addition, it features a refractive index-symmetrical geometry that promotes the generation of cLSPs and leads to strong suppression of radiative losses, narrowing the spectral width of the resonance, and increasing of the electromagnetic field intensity. Narrowing of the cLSP spectral band down to 13 nm and its reversible shifting by up to 151 nm is observed in the near infrared part of the spectrum by varying temperature and by solvent exchange for systems with a poly(N-isopropylacrylamide)-based hydrogel membrane that is allowed to reversibly swell and collapse in either one or in three dimensions. The reported structures with embedded periodic gold nanoparticle arrays are particularly attractive for biosensing applications as the open hydrogel structure can be efficiently post-modified with functional moieties, such as specific ligands, and since biomolecules can rapidly diffuse through swollen polymer networks. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemHybrid Optical Fibers – An Innovative Platform for In‐Fiber Photonic Devices(Weinheim : Wiley-VCH, 2015) Alexander Schmidt, Markus; Argyros, Alexander; Sorin, FabienThe field of hybrid optical fibers is one of the most active research areas in current fiber optics and has the vision of integrating sophisticated materials inside fibers, which are not traditionally used in fiber optics. Novel in-fiber devices with unique properties have been developed, opening up new directions for fiber optics in fields of critical interest in modern research, such as biophotonics, environmental science, optoelectronics, metamaterials, remote sensing, medicine, or quantum optics. Here the recent progress in the field of hybrid optical fibers is reviewed from an application perspective, focusing on fiber-integrated devices enabled by including novel materials inside polymer and glass fibers. The topics discussed range from nanowire-based plasmonics and hyperlenses, to integrated semiconductor devices such as optoelectronic detectors, and intense light generation unlocked by highly nonlinear hybrid waveguides.