Chiral-at-Molybdenum – A Computational Study on N-Substituted cis-MoO2(nacnac)2

Cis-MoO₂(nacnac)₂ (nacnac=β-diketiminate) can be a viable chiral-at-metal catalyst when its two β-diketiminate (nacnac) ligands are N-substituted to prevent Λ⇌Δ racemization. Even simple methyl groups raise the barriers for racemization significantly for the Bailar, Rây-Dutt, Conte-Hippler, and Dhimba-Muller-Lammertsma (DML) twists to a respectable 28.5, 37.8, 30.5, and 25.1 kcal/mol, respectively, at ωB97X-D/6-311+G(2d,p) (LANL2DZ for Mo) including acetonitrile solvation. The lowest energy DML barrier increases to ΔG^o=27.4 kcal/mol with N-substituted t-butyl groups. The nacnac ligands’ electronic and steric components to the racemization barriers are discussed.     

Interactions of Ionic Liquids with Polysaccharides – 2: Cellulose

Some general comments about ionic liquids (ILs) and carbohydrates are given. The main scope of the review is to discuss the present state of the art of chemical modification of cellulose applying IL as reaction media considering own research results. ILs, namely 1-butyl-3-methylimidazolium chloride (BMIMCl), 1-ethyl- 3-methylimidazolium chloride (EMIMCl), 1-butyl-2,3-dimethylimidazolium chloride (BDMIMCl), 1-allyl-2,3-dimethylimidazolium bromide (ADMIMBr) and 1-ethyl-3- methylimidazolium acetate (EMIMAc) are solvents for cellulose (even for high molecular bacterial synthesized cellulose) and can easily be applied as reaction media for cellulose modification. We investigated the homogeneous acylation, carbanilation and silylation of the biopolymer cellulose. Under mild conditions and within short reaction time at low temperature (65 °C to 80 °C) and low excess of reagent, various cellulose esters and carbanilates, dendronized cellulose and trimethylsilyl cellulose were obtained. The DS of the cellulose derivatives can be controlled by varying the reaction time, reaction temperature and the IL used as reaction medium.     

EuPtSn2 – A Stannide with Sn2 Dumbbells in a Three-dimensional [PtSn2]2– Polyanion

EuPtSn₂ was obtained by melting of the elements in a sealed tantalum ampoule followed by an annealing sequence for crystal growth. The EuPtSn₂ sample was studied through its Guinier powder pattern and the structure was refined from single-crystal X-ray diffractometer data: CeRhSn₂ type, Cmcm, a = 472.05(3), b = 1724.19(12), c = 957.36(7) pm, wR₂ = 0.0388, 879 F² values and 30 variables. The platinum and tin atoms build up a three-dimensional [PtSn₂]^2– polyanionic network which consists of distorted PtSn₅ square pyramids (265–278 pm Pt–Sn) and Sn₂ dumbbells with 281 and 299 pm Sn–Sn distances. The structural relationship with DyRhGe₂ and Ce₃Pt₄Ge₆ is discussed. EuPtSn₂ shows Curie–Weiss behavior with an experimental magnetic moment of 7.78(1) μ_B / Eu, indicating stable divalent europium. This is corroborated by ¹⁵¹Eu Mössbauer spectroscopy. Antiferromagnetic ordering is detected below 3.4 K. Specific heat measurements confirm the magnetic ordering and indicate a second phase transition through a clear λ-type signal at 7.3 K which might be associated with a structural distortion.     

Organodiphosphines in cis-Pt(η2-P2L)(SR)2 derivatives – structural aspects

Abstract

This review covers 30?Pt(II) complexes in which the inner coordination of PtP₂S₂ is created by organodiphosphines and a pair of S-donor ligands. The organodiphosphines generate four-(PCP), five-(PC₂P), six-(PC₃P) and seven-(PC₄P) membered metallocyclic rings. These complexes crystallize in three crystal systems: orthorhombic (four examples), triclinic (nine examples) and monoclinic (seventeen examples). The respective metallocyclic rings open in the sequence: (mean values): 73.2° (PCP) < 86.0° (PC₂P) < 94.5° (PC₃P) < 97.5° (PC₄P). The mean values of Pt-P and Pt-S bond distances are 2.247 and 2.350?Å, respectively. The structure parameters are analyzed and discussed with attention to any trans-influence.     

Organodiphosphines in cis-Pt(η2-P2L)(η2-S2L) derivatives – structural aspects

Abstract

In this review structural parameters of forty complexes with an inner coordination sphere of Pt(η²-P₂L)(η²-S₂L) are analyzed and classified These complexes crystallize in three crystal systems: orthorhombic (four examples), triclinic (six examples) and monoclinic (thirty examples). The organodiphosphines create four- (PCP), five- (PC₂P), six- (PC₃P) and seven- (PC₄P) membered metallocyclic rings with mean P-Pt-P bite angle values of 72.5° (PCP) < 85.3° (PC₂P) < 93.0° (PC₃P) < 97.4° (PC₄P). The dithiolates create four- (SCS), five- (SC₂S), six- (SC₃S; SCSCS; SPNPS; SPCPS) and seven- (SC₄S) membered metallocyclic rings with mean S-Pt-S bite angle values of 74.5° (SCS) < 85.8° (SCSCS) < 87.0° (SPNPS) < 89.0° (SC₂S) < 92.3° (SC₄S) < 93.5° (SC₃S) < 97.5° (SPCPS). The mean Pt-P and Pt-S bond distances are 2.257 and 2.328?Å, respectively. The data are compared with those found in complexes with inner coordination spheres of Pt(PL)₂(SL)₂, Pt(PL)₂(η²-S₂L) and Pt(η²-P₂L)(SL)₂.     

MoS2-Based Catalysts for N2 Electroreduction to NH3 – An Overview of MoS2 Optimization Strategies

The nitrogen reduction reaction (NRR) has become an ideal alternative to the Haber-Bosch process, as NRR possesses, among others, the advantage of operating under ambient conditions and saving energy consumption. The key to efficient NRR is to find a suitable electrocatalyst, which helps to break the strong N≡N bond and improves the reaction selectivity. Molybdenum disulfide (MoS₂) as an emerging layered two-dimensional material has attracted a mass of attention in various fields. In this minireview, we summarize the optimization strategies of MoS₂-based catalysts which have been developed to improve the weak NRR activity of primitive MoS₂. Some theoretical predictions have also been summarized, which can provide direction for optimizing NRR activity of future MoS₂-based materials. Finally, an outlook about the optimization of MoS₂-based catalysts used in electrochemical N₂ fixation are given.     

Fluoride-conducting Electrolytes Based on Doped Oxyfluorides Pb1 – xAlxF2 + x–2yOy

Employing materials with fast transport of fluoride ions in chemical power sources and gas sensors requires synthesizing new materials with a wide range of electric properties. High conductivity of -PbF₂can be provided by introducing trivalent ions, which create excess concentration of fluoride ions in -PbF₂. Experimental data on the ionic conductivity of Pb_{1 – x} M _x F_{2 + x} , where M is In, Sb, or Bi, are presented in [1–3]. For the first time brief information about high ionic conductivity of doped Pb_{1 – x} Al _x F_{2 + x– 2y} O _y was reported in [4]. Here, we study in greater detail ionic conduction of neat Pb_{1 – x} Al _x F_{2 + x– 2y} O _y and that doped with fluorides of transition metals Zn, Cu, Ni, Co, Mn, Cr, V, or Ti in the temperature range 272–473 K.     

Hydrogen Bonds at Silica – Polyvinylpyrrolidone – Water Interfaces

The effect of the adsorption of polyvinylpyrrolidone on the surface of highly dispersed silica on the state of interfacial water was studied by ¹H NMR spectroscopy and thermally stimulated depolarization with freezing out of the bulk water.     

Preillumination – Induced change of electronic transport properties of TlGaSe2 semiconductor

The effect of the preillumination on the dark and the photo-conductivity of the TlGaSe₂ layered semiconductor is investigated within the temperature range of 80–300 K. After the illumination predominantly at high temperatures, a substantial decrease in both dark and photo-conductivities was observed. Observed phenomena resemble the Staebler–Wronski effect, which is typical for the amorphous semiconductors. The main contribution of this work is to show that the TlGaSe₂ single crystals with well apparent crystalline structure can demonstrate certain characteristics peculiar to amorphous semiconductors.     

Naringenin and quercetin – potential anti-HCV agents for NS2 protease targets

Nonstructural proteins of hepatitis C virus had drawn much attention for the scientific fraternity in drug discovery due to its important role in the disease. 3D structure of the protein was predicted using molecular modelling protocol. Docking studies of 10 medicinal plant compounds and three drugs available in the market (control) with NS2 protease were employed by using rigid docking approach of AutoDock 4.2. Among the molecules tested for docking study, naringenin and quercetin revealed minimum binding energy of ? 7.97 and ? 7.95 kcal/mol with NS2 protease. All the ligands were docked deeply within the binding pocket region of the protein. The docking study results showed that these compounds are potential inhibitors of the target; and also all these docked compounds have good inhibition constant, vdW+Hbond+desolv energy with best RMSD value.     

Li2MnBr4(o-rh.) – eine geordnete NaCl-Defektstruktur des SnMn2S4-Typs

Li₂MnBr₄(o-rh.) – an Ordered NaCl Defect Structure of the SnMn₂S₄ Type Neutron diffraction data of Li₂MnBr₄ at 25°C are presented. The orthorhombic room-temperature polymorph of Li₂MnBr₄ (space group Cmmm, Z = 2, a = 777.78(4), b = 1106.58(5), and c = 388.18(2) pm, R_I = 6.7%) crystallizes in an ordered NaCl defect structure (SnMn₂S₄ type). The tetragonally distorted MBr₆ octahedra are elongated in the case of LiBr₆ and compressed for MnBr₆ owing to the different sharing of these units. The crystal structure of Li₂MnBr₄ oC14 (and those of alternative structure models with a larger pseudotetragonal cell) are discussed with respect to X-ray intensities, Madelung part of lattice energy (MAPLE), and the Raman spectra. The symmetry coordinates and vibrational modes of the \documentclass{article}\pagestyle{empty}\begin{document}$ (\mathop {\rm k}\limits^ \to = 0) $\end{document} phonons of Li₂MnBr₄ oC14 are given.     

SPIROPHOSPHORANES – STRUCTURE REACTIVITY

Abstract

The first part of this article will deal with the reactions of spirophosphoranes with a P[sbnd]H bond. These compounds contain two five-membered rings and have four oxygen atoms, or three oxygen atoms and one nitrogen atom, or two oxygen and two nitrogen atoms directly bonded to the phosphorus atom, which in all cases bears an hydrogen atom (Scheme 1). The most remarkable property of these compounds is undoubtedly their ability to give rise to a tautomeric equilibrium between the tri- and penta-coordinated structures P_III→P_V.     

Lithium-cation Conduction and Crystallochemical Features of Solid Solutions La2/3 – x Li3x□4/3 – 2x Nb2O6 with the Structure of Fault Perovskite

Transport properties and crystallochemical features of lithium-containing lanthanum metaniobates La_{2/3 – x} Li_{3x4/3 – 2x} Nb₂O₆ with the structure of fault perovskite are studied. The materials studied have high conductivity by lithium ions. A correlation between the conductivity magnitude, chemical composition, and crystallographic parameters is found.     

The Crystal Structure of the 2 : 1 Cholic Acid – Benzophenone Clathrate

The 2 : 1 cholic acid – benzophenone clathratecrystallizes in the space group P2_1 withthe unit-cell parameters a = 25.498(6),b = 7.942(1), c = 28.309(6) Å, = 101.85(2)°. There are four symmetricallyindependent host molecules in the unit cell: two ofthem with the steroidal side chain assuminggauche and the remaining two with the side chain in thetrans conformation. Pairs of the host moleculesadopting similar conformations alternate along the[201] direction of the bilayer. The guestmolecules are accommodated in two crystallographicallyindependent but topologically similar channelsrunning parallel to [010]. Benzophenone molecules aredisordered and included in each channel in twodifferent conformations.     

Molecular recognition by indoleacetic acid-imprinted polymers – effects of 2-hydroxyethyl methacrylate content

Molecularly imprinted polymers for indole-acetic acid were prepared by co-polymerizing N,N-dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate. The dependence of the affinity and selectivity of the imprinted polymers on HEMA content was evaluated chromatographically. The affinity was improved by increasing the HEMA content; the selectivity of the imprinted polymer was best when the HEMA content was approximately 30%, irrespective of monomer content.     

Iodophthalocyaninato(2–)thallium(III) – Synthese und Kristallstruktur

Iodophthalocyaninato(2–)thallium(III) – Synthesis and Crystal Structure Oxidation of dithalliumphthalocyaninate(2–) with excess iodine yields crystalline, blue-green iodophthalocyaninato(2–)thallium(III). It crystallizes in the orthorhombic space group Pnma (no. 62) with lattice parameters: a = 13.778(3) Å, b = 14.649(2) Å, c = 14.907(1) Å, Z = 4. The Tl atom coordinates four N_iso atoms (isoindole N atoms) and one I atom in a tetragonal pyramidal arrangement. The Tl atom is located out of the centre of the (N_iso)₄ plane towards the iodine atom by 0.959(3) Å. The Tl–I distance is 2.674(1) Å, the Tl–N_iso distances range from 2.20(1) to 2.23(1) Å (average 2.22(1) Å). The phthalocyaninate(2–) is severely distorted from planarity (concave distortion).     

Lotus-Effect® – surfaces

Surfaces are often characterized with phrases like “easy to clean”, “dirt repellent”, “dirt resistant”, “self cleaning” or “ Lotus -Effect^®”. Every one of those phrases is used to describe a behavior of surfaces - similar to each other but still different. This article is providing the definition of the Lotus -Effect^®, techniques to manufacture self cleaning surfaces and methods to characterize them as well. How to generate a self cleaning surface depends on the substrate and the use later on. It can be as easy as a spray on but on the other hand as complicated as a three step process. Self cleaning surfaces are defined by four parameters - contact angle, roll-off angle, hystereses and C.I.E-Lab Δ-L value.