Application of a chiral metal-organic framework in enantioselective separation

A modular approach for the synthesis of highly ordered porous and chiral auxiliary (Evans auxiliary) decorated metal-organic frameworks is developed. Our synthesis strategy, which uses known porous structures as model materials for incorporation of chirality via linker modification, can provide access to a wide range of porous materials suitable for enantioselective separation and catalysis. Chiral analogues of UMCM-1 have been synthesized and investigated for the enantioseparation of chiral compounds in the liquid phase and first promising results are reported.     

A highly porous flexible Metal-Organic Framework with corundum topology

A flexible Metal-Organic Framework Zn(4)O(BenzTB)(3/2) (DUT-13) was obtained by combination of a tetratopic linker and Zn(4)O(6+) as connector. The material has a corundum topology and shows the highest pore volume among flexible MOFs.     

Local coordination of Fe3+ in Li[Co(0.98)Fe(0.02)]O2 as cathode material for lithium ion batteries-multi-frequency EPR and Monte-Carlo Newman-superposition model analysis

The local coordination of the Fe(3+)-centers in Li[Co(0.98)Fe(0.02)]O(2) cathode materials for lithium-ion batteries has been investigated by means of XRD and multi-frequency EPR spectroscopy. EPR clearly showed the Fe(3+) being in a high-spin state with S = 5/2. The set of spin-Hamiltonian parameters obtained from multi-frequency EPR experiments with Larmor frequencies ranging between 9.8 and 406 GHz was transformed into structural information by means of an expansion to standard Newton-superposition modeling, termed as Monte-Carlo Newman superposition modeling. Based on this analysis, an isovalent incorporation of the Fe(3+)-ions on the Co(3+)-sites, i.e. Fe(x)(Co), has been shown. With that respect, the positive sign of the axial second-order fine-structure interaction parameter B(0)(2) is indicative of an elongated oxygen octahedron, whereas B(0)(2) < 0 points to a compressed octahedron coordinated about the Fe(3+)-center. Furthermore, the results obtained here suggest that the oxygen octahedron about the Fe(3+)-ion is slightly distorted as compared to the CoO(6) octahedron, which in turn may impose mechanical strain to the cathode material.     

Fenchel Duality Theory and a Primal-Dual Algorithm on Riemannian Manifolds

Foundations of Computational Mathematics - This paper introduces a new notion of a Fenchel conjugate, which generalizes the classical Fenchel conjugation to functions defined on Riemannian...     

Integraleigenschaften der adjungirten Kegelfunctionen

Ohne Zusammenfassung     

A family of 2D and 3D coordination polymers involving a trigonal tritopic linker

Five new coordination polymers, namely, [Zn(2)(H(2)O)(2)(BBC)](NO(3))(DEF)(6) (DUT-40), [Zn(3)(H(2)O)(3)(BBC)(2)] (DUT-41), [(C(2)H(5))(2)NH(2)][Zn(2)(BBC)(TDC)](DEF)(6)(H(2)O)(7) (DUT-42), [Zn(10)(BBC)(5)(BPDC)(2)(H(2)O)(10)](NO(3))(DEF)(28)(H(2)O)(8) (DUT-43), and [Co(2)(BBC)(NO(3))(DEF)(2)(H(2)O)](DEF)(6)(H(2)O) (DUT-44), where BBC--4,4',4'-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate, TDC--2,5-thiophenedicarboxylate, BPDC--4,4'-biphenyldicarboxylate, DEF--,N-diethylformamide, were obtained under solvothermal conditions and structurally characterized. It has been shown that compounds DUT-40, DUT-41 and DUT-44 exhibit 2D layered structures with large hexagonal channels. Utilization of additional angular dicarboxylic TDC linker led to the formation of the DUT-42 compound with the structure consisting of three interpenetrated 3D networks. Using the linear co-linker dicarboxylic BPDC, DUT-43 was obtained which forms a complicated 3D architecture arising from the polycatenation of triple-layered 2D building units and 2D single layer units. The pore accessibility of the synthesized compounds in the liquid phase was proved by the adsorption of dye molecules.     

Non-oxo vanadium(IV) alkoxide chemistry: solid state structures, aggregation equilibria and thermochromic behaviour in solution

The reversible thermochromic behaviour of homoleptic [{V(OR)(4)}(n)] complexes in solution [R = Pr(i) (product I), Bu(s) (B(s)), Nep (N) and Cy (C)] is accounted for the existence of an aggregation equilibrium involving dimeric and monomeric species in which vanadium(iv) is respectively five- and four-coordinate. Bulky R groups such as Bu(t) and Pe(t) (tert-pentoxide) prevent aggregation and therefore give rise to exclusively mononuclear compounds (B(t) and P(t), respectively) that are not thermochromic. The complexes and their temperature-dependent interconversion were characterised by single crystal X-ray diffractometry, magnetic susceptibility measurements and electronic, FTIR and EPR spectroscopies in a wide temperature range. Equilibrium constants and enthalpy and entropy changes for the dimerization reactions have been determined and compared with literature data.     

Data compression and prediction in neural networks

We study the relationship between data compression and prediction in single-layer neural networks of limited complexity. Quantifying the intuitive notion of Occam's razor using Rissanen's minimum complexity framework, we investigate the model-selection criterion advocated by this principle. While we find that the criterion works well for large sample sizes (as it must for consistency), the behavior for finite sample sizes is rather complex, depending intricately on the relationship between the complexity of the hypothesis space and the target space. We also show that the limited networks studied perform efficient data compression, even in the error full regime.