Four sets of polymers from norbornene-type monomers with various carbocyclic groups were prepared to perform the structure-property study and to evaluate the effect of main- and side-chains on the ...porosity of resultant polymers. As monomers, norbornenes with phenyl-, cyclohexyl-, norbornyl-, and framed carbocyclic-groups were designed and synthesized using the Diels-Alder reaction in good yields. All these monomers were involved in ring-opening metathesis and vinyl-addition polymerization to form polymers with various structure of main-chains. The porosity was investigated with help of low temperature nitrogen adsorption/desorption method, and the sorption of H2, CO2, CH4 were also assessed for the most promising synthesized polymers. The obtained polymers exhibited large BET surface areas (up to 740 m2/g), while CO2 and H2 uptake reached 3.0 and 0.18 mmol/g, correspondingly. The porosity of polymers was shown to be determined by the nature of both backbones and side-chains, and it seems that the influence of side-chains is the main one. The largest values of BET surface areas were achieved for polynorbornenes with framed carbocyclic groups. At the same time, vinyl-addition polynorbornenes, which have more rigid main-chains, also provided larger BET surface areas compared to isomeric metathesis ones. Therefore, new valuable relationships between polymer structure and its porosity were established, and an efficient strategy to readily available soluble microporous polymers from norbornene derivatives was suggested. The combination of comparatively simple synthesis, high porosity and solubility in organic solvents can be considered as a key advantage of the synthesized polymers.
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•Structure-property study of polynorbornenes with various carbocycles in side chains.•Soluble and readily available microporous polymers with large surface area.•The effect of main- and side-chains on the porosity was studied.•Large values of surface area are for polymers with framed carbocyclic groups.
A sandwich-type rhodium polyoxotungstate with unprecedented tetrarhodium-oxo core Na(12)(Rh(4)(μ(3)-O)(2)(H(2)O)(2))(H(2)W(9)O(33))(2)·38H(2)O (1) was obtained by hydrothermal reaction of rhodium(II) ...acetate and sodium tungstate; crystal structure was determined by X-ray diffractometry and was confirmed by (183)W NMR data; 1 is active in electrocatalytic water oxidation.
New Ru-containing polyoxometalate PW11O39RuII(NO)4‑ (1 4‑) was obtained in high yield by reaction of Ru(NO)Cl52‑ with PW11O397‑ and characterized by multinuclear NMR, cyclic voltammetry, IR ...spectroscopy, and electrospray ionization mass spectrometry (ESI-MS). The intrinsic reactivity of the {RuNO} site in 1 4‑ toward various reagents has been studied using a versatile and simple ESI tandem mass spectrometric methodology for identification of the L attached at the Ru site; this approach relies on the preferential liberation of the L ligands attached at the Ru sites upon mass-selecting desired intermediates and subsequent promotion of their fragmentation. Reactions with both hydrazine and hydroxylamine lead to elimination of the nitroso group and quantitative formation of PW11O39RuIII(H2O)4‑ (2 4‑) in aqueous solution. In the reaction with hydroxylamine, an intermediate with coordinated dinitrogen has been detected. An easy access to the NH3-coordinated PW11O39RuNH34‑ (3 4‑) complex was achieved upon reduction of 1 4‑ with Sn2+ in water.
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•Pulsed laser ablation of iron in air led to magnetite and iron nitrides formation.•Lamellas and rolls appear in the sample that was ablated in air, not in Ar-O2 mixture.•Thermal ...treatment allowed control of the composition and structure of the material.•Materials obtained with different properties are in demand for different applications.
Magnetic nanoparticles were obtained using the nanosecond pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) of an iron target in air at atmospheric pressure. The particles obtained were further annealed at four different temperatures. The composition, structure and properties of all obtained powders were investigated using X-ray diffraction (XRD), DSC, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, TEM, SAED and other techniques. The initial sample was found to contain monoclinic magnetite and iron nitrides. Presumably, magnetite presents in the form of spherical particles with the distribution maximum of 12–15 nm, and nitrides take the form of lamellas and rolls. Thermal treatment of the sample led to particle enlargement and phase transformations, first, to cubic magnetite, then to a Fe3O4, α-Fe2O3 and γ-Fe2O3 mixture, and finally to the pure hematite phase. Zeta-potential, BET surface area and magnetic properties changed with the annealing as well. The obtained materials exhibited different properties that make them in demand in different fields, from biomedicine to technology.
Abstract
When Heisenberg spins interact antiferromagnetically on a triangular lattice and nearest-neighbor interactions dominate, the ground state is 120° antiferromagnetism. In this work, we probe ...the response of this state to lifting the triangular symmetry, through investigation of the triangular antiferromagnet PdCrO
2
under uniaxial stress by neutron diffraction and resistivity measurements. The periodicity of the magnetic order is found to change rapidly with applied stress; the rate of change indicates that the magnetic anisotropy is roughly forty times the stress-induced bond length anisotropy. At low stress, the incommensuration period becomes extremely long, on the order of 1000 lattice spacings; no locking of the magnetism to commensurate periodicity is detected. Separately, the magnetic structure is found to undergo a first-order transition at a compressive stress of ∼0.4 GPa, at which the interlayer ordering switches from a double-to a single-
q
structure.
The first Keggin-type heteropolyanion, PW(11)O(39)Ir(H(2)O)(4-) (1), was synthesized by hydrothermal reaction from two different polytungstate precursors and IrF(6)(2-). It was isolated as ...(Bu(4)N)(4)PW(11)O(39)Ir(H(2)O) (1a), which was completely characterized by multinuclear (31)P and (183)W NMR, ESI-mass spectrometry and cyclic voltammetry. A rapid screening methodology to ascertain the intrinsic substitutional lability at the Ir site is also presented, based on ESI-MS.
A new synthetic entry to iridium Keggin‐type polyoxometalate complexes from PW11O397– and K3IrCl6 under harsh conditions is reported. The complex PW11O39IrCl5– (15–) featuring an IrCl functionality ...was obtained in high yield and characterized by NMR spectroscopic and ESI‐MS techniques. The presence of Li+ (3–4 M) is essential for a quantitative yield of 15–. The reactivities of 15– and its rhodium analogue PW11O39RhCl5– in ligand substitution at the noble metal site were studied. Thiocyanate coordination successfully yielded (Bu4N)5PW11O39M(SCN) M = Rh (2a), Ir, (3a). In both cases, the SCN ligands are coordinated by sulfur atoms, according to 13C NMR and IR spectroscopic data. Gas‐phase fragmentation reactions of compounds 2a and 3a were also investigated by collision‐induced dissociation (CID) experiments. Reaction of PW11O39RhCl5– with NaN3 resulted in Cl– to OH– replacement accompanied by the liberation of the RhCl fragment, whereas 15– proved unreactive with NaN3. Attempts to coordinate NO2– are adversely affected by competing noble metal excision with formation of free PW11O397–.
Applying in-plane uniaxial pressure to strongly correlated low-dimensional systems has been shown to tune the electronic structure dramatically. For example, the unconventional superconductor Sr 2 ...RuO 4 can be tuned through a single Van Hove point, resulting in strong enhancement of both T c and H c2 . Out-of-plane ( c axis) uniaxial pressure is expected to tune the quasi-two-dimensional structure even more strongly, by pushing it towards two Van Hove points simultaneously. Here, we achieve a record uniaxial stress of 3.2 GPa along the c axis of Sr 2 RuO 4 . H c2 increases, as expected for increasing density of states, but unexpectedly T c falls. As a first attempt to explain this result, we present three-dimensional calculations in the weak interaction limit. We find that within the weak-coupling framework there is no single order parameter that can account for the contrasting effects of in-plane versus c -axis uniaxial stress, which makes this new result a strong constraint on theories of the superconductivity of Sr 2 RuO 4 .
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