Synthesis, Raman spectra and crystal structures of [Cu(XeF2)n](SbF6)2 (n=2, 4)

Pure [Cu(XeF2)2](SbF6)2 was prepared by the reaction of Cu(SbF 6) 2 with a stoichiometric amount of XeF2 in anhydrous hydrogen fluoride (aHF) at ambient temperature. The reaction between Cu(SbF6)2 and XeF2 (1:4 molar ratio) in aHF yielded [Cu(XeF2)4](SbF6)2 contaminated with traces of Xe 2F 3SbF6 and CuF2. The 6-fold coordination of Cu(2+) in [Cu(XeF2)2](SbF6)2 includes two fluorine atoms from two XeF2 ligands and four fluorine atoms provided by four [SbF6](-) anions. The neighboring [Cu(XeF 2)2](2+) moieties are connected via two [SbF6] units, with the bridging fluorine atoms in cis positions, into infinite [Cu(eta(1)-XeF2)2](cis-eta(2)-SbF 6)2[Cu(eta(1)-XeF 2)2] chains. Because of the high electron affinity of Cu(2+), coordinated XeF2 shows the highest distortion (Xe-Fb=210.2(5) pm, Xe-Ft=190.6(5) pm) observed so far among all known [M(x+)(XeF2)n](A)x (A=BF4, PF6, etc.) complexes. The four equatorial coordination sites of the Cu(2+) ion in [Cu(XeF 2) 4](SbF6)2 are occupied by four XeF 2 ligands. Two fluorine atoms belonging to two [SbF6] units complete the Cu (2+) coordination environment. The neighboring [Cu(XeF2)4](2+) species are linked via one [SbF6] unit, with bridging fluorine atoms in trans positions, into linear infinite [Cu(eta(1)-XeF2)4](trans-eta(2)-SbF6)[Cu(eta(1)-XeF2)4] chains. To compensate for the remaining positive charge, crystallographically independent [SbF6](-) anions are located between the chains and are fixed in the crystal space by weak Xe...F(Sb) interactions.     

Crystal Growth and Crystal Structures of Gold(V) Compounds: Cu(AuF6)2, Ag(AuF6)2, and O2(CuF)3(AuF6)4 ⋅ HF

Crystal growth from anhydrous hydrogen fluoride solutions of M²⁺ (M=Cu, Ag) and [AuF₆]⁻ gave M(AuF₆)₂ salts (M=Cu, Ag). Similar attempts to prepare single crystals of the corresponding nickel, zinc and magnesium salts failed. The crystal structure of Cu(AuF₆)₂ consists of layers of Cu²⁺ cations connected by [AuF₆]⁻ anions, thus forming slabs. Only van der Waals interactions exist between adjacent slabs. The crystal structure of Ag(AuF₆)₂ consists of a three-dimensional framework in which Ag⁺ cations are linked by [AuF₆]⁻ anions. Both structures are members of the M^II(X^VF₆)₂ family, in which seven different structure types have been observed to date. In the crystal structure of O₂(CuF)₃(AuF₆)₄ ⋅ HF, the bridging AuF₆ units connect [−Cu−F−Cu−F−]_∞ chains to form stacks between which O₂⁺ cations and HF molecules are located.     

Bioelectronic Interface Connecting Reversible Logic Gates Based on Enzyme and DNA Reactions

It is believed that connecting biomolecular computation elements in complex networks of communicating molecules may eventually lead to a biocomputer that can be used for diagnostics and/or the cure of physiological and genetic disorders. Here, a bioelectronic interface based on biomolecule‐modified electrodes has been designed to bridge reversible enzymatic logic gates with reversible DNA‐based logic gates. The enzyme‐based Fredkin gate with three input and three output signals was connected to the DNA‐based Feynman gate with two input and two output signals—both representing logically reversible computing elements. In the reversible Fredkin gate, the routing of two data signals between two output channels was controlled by the control signal (third channel). The two data output signals generated by the Fredkin gate were directed toward two electrochemical flow cells, responding to the output signals by releasing DNA molecules that serve as the input signals for the next Feynman logic gate based on the DNA reacting cascade, producing, in turn, two final output signals. The Feynman gate operated as the controlled NOT gate (CNOT), where one of the input channels controlled a NOT operation on another channel. Both logic gates represented a highly sophisticated combination of input‐controlled signal‐routing logic operations, resulting in redirecting chemical signals in different channels and performing orchestrated computing processes. The biomolecular reaction cascade responsible for the signal processing was realized by moving the solution from one reacting cell to another, including the reacting flow cells and electrochemical flow cells, which were organized in a specific network mimicking electronic computing circuitries. The designed system represents the first example of high complexity biocomputing processes integrating enzyme and DNA reactions and performing logically reversible signal processing.     

Lithium intercalation into TiS<Subscript>2</Subscript> cathode material: phase equilibria in a Li–TiS<Subscript>2</Subscript> system

Lithium-intercalated titanium disulfide Li _x TiS₂ had been extensively studied as prototypical cathode material for high-energy-density reversible lithium batteries with moderate voltage. Today, this phase is one of the leading candidates for all-solid-state lithium batteries with durable high energy and high rate performance. However, fundamental knowledge of Li⁺ insertion into TiS₂ is still incomplete; available information on the phase diagram of the Li–TiS₂ system is limited by x?=?1 due to difficulties in preparing lithium-rich equilibrated samples. The goals of this work were to re-examine Li _x TiS₂ single phase boundaries and to clarify the existence of lithium-rich intercalates with x?>?1. А new preparation technique was developed to obtain 1T-Li _x TiS₂ samples as good-quality equilibrated products with desirable lithium content. Phase equilibria in a quasibinary Li–TiS₂ system were studied by X-ray diffraction, emf measurements (25 °C) and thermal analysis (25–350 °C) over a wide range of Li:Ti ratios (0 to 4).     

Graphene‐Functionalized 3D‐Carbon Fiber Electrodes – Preparation and Electrochemical Characterization

Graphene nanosheets were produced on the surface of carbon fibers by in situ electrochemical procedure including oxidative and reductive steps to yield first graphene oxide, later converted to graphene. The electrode material composed of graphene‐functionalized carbon fibers was characterized by scanning electron microscopy (SEM) and cyclic voltammery demonstrating superior electrochemical kinetics comparing with the original carbon paper. The interfacial electron transfer rate for the reversible redox process of [Fe(CN)₆]^3?/4? was found ca. 4.5‐fold higher after the electrode modification with the graphene nanosheets. The novel electrode material is suggested as a promising conducting interface for bioelectrocatalytic electrodes used in various electrochemical biosensors and biofuel cells, particularly operating in vivo.     

An Enzyme‐Based Half‐Adder and Half‐Subtractor with a Modular Design

A half‐adder and a half‐subtractor have been realized using enzymatic reaction cascades performed in a flow cell device. The individual cells were modified with different enzymes and assembled in complex networks to perform logic operations and arithmetic functions. The modular design of the logic devices allowed for easy re‐configuration, enabling them to perform various functions. The final output signals, represented by redox species [Fe(CN)₆]^3?/4? or NADH/NAD⁺, were analyzed optically to derive the calculation results. These output signals might be applicable in the future for actuation processes, for example, substance release activated by logically processed signals.     

Lower bounds for numbers of real solutions in problems of Schubert calculus

We give lower bounds for the numbers of real solutions in problems appearing in Schubert calculus in the Grassmannian \({\mathop{\rm Gr}(n,d)}\) related to osculating flags. It is known that such solutions are related to Bethe vectors in the Gaudin model associated to \({\mathop{\rm gl}_n}\). The Gaudin Hamiltonians are self-adjoint with respect to a non-degenerate indefinite Hermitian form. Our bound comes from the computation of the signature of that form.     

Synthesis of nitrogen-containing spirocyclic scaffolds via aminoallylation/RCM sequence

A concise route to nitrogen-containing spirocyclic scaffolds was developed. It is based on the allylation of imines derived from cyclic ketones. The resulting homoallylamines were subsequently alkylated with bromomethylmethacrylate resulting in propenyl-butenyl substituted amine derivatives. Basic amines such as 4 or 10 were cyclized with the Grubbs 2nd generation catalyst in the presence of pTsOH. Carbamate derivatives could be converted to tetrahydropiperidine derivatives with the same catalyst. It could be shown that the acrylate functionality can be degraded to the ketone using the classical sequence consisting of Curtius rearrangement of the derived acrylic acid followed by hydrolysis of the vinyl isocyanate. Other modifications include reduction of the acrylate double bond, saponification of the ester group, and amide formation.     

DNA interaction with synthetic polymers in solution

DNA complexes with cationic polymers (polyvinylamine (PVA), polyallylamine (PAA), polydimethylaminoethylmethacrylate (PDMAEM), poly-(N,N,N-trimethylammonio)ethyl methacrylate chloride (PTMAEM), poly-l-lysine (PLL)) were investigated. It was shown that volume and persistent length of DNA do not change essentially at low cationic polymer concentration in a solution. DNA packaging in 0.005 M NaCl was observed at charge ratio N/P ≈ 1. Secondary DNA structure in complexes was not disrupted, and DNA was protected from protonation. The comparison between DNA packaging in complexes with polycations and DNA condensation induced by trivalent ions was made.