22 resultados para crystal structure and symmetry
em Deakin Research Online - Australia
Resumo:
The syntheses of cyclo-[R2Sn(OPPh2O)2SnR2](O3SCF3)2 (R = Me (1), t-Bu (2)) by the consecutive reaction of R2SnO (R = Me, t-Bu) with triflic acid and diphenylphosphinic acid are presented. In the solid state, 1 and 2 were investigated by 119Sn MAS and 31P MAS NMR spectroscopy as well as X-ray crystallography and appear to exist as ion pairs of cyclo-[R2Sn(OPPh2O)2SnR2]2+ dications and triflate anions. In solution, 1 and 2 are involved in extensive equilibria processes featuring cationic diorganotin(IV) species with Sn-O-P linkages, as evidenced by 119Sn and 31P NMR spectroscopy, electrospray mass spectrometry, and conductivity measurements.
Resumo:
Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) have received great attention during the past decade due to their giant magnetic shape memory effect and fast dynamic response. The crystal structure and crystallographic features of two Ni-Mn-Ga alloys were precisely determined in this study. Neutron diffraction measurements show that Ni48Mn30Ga22 has a Heusler austenitic structure at room temperature; its crystal structure changes into a seven-layered martensitic structure when cooled to 243K. Ni53Mn25Ga22 has an I4/mmm martensitic structure at room temperature. Electron backscattered diffraction (EBSD) analyses reveal that there are only two martensitic variants with a misorientation of ~82° around <110> axis in each initial austenite grain in Ni53Mn25Ga22. The investigation on crystal structure and crystallographic features will shed light on the development of high-performance FSMAs with optimal properties.
Resumo:
Calcium hydrogenmelonate heptahydrate Ca[HC6N7(NCN)3]·7H2O was obtained by metathesis reaction in aqueous solution. The structure of the molecular salt was elucidated by single-crystal X-ray diffraction. The crystal structure consists of alternating layers of planar monopronated melonate ions, Ca2+ and crystal water molecules. The anions of adjacent layers are staggered so that no π–π stacking occurs. The melonate entities are interconnected by hydrogen bonds within and between the layers. Ca[HC6N7(NCN)3]·7H2O was investigated by solid-state NMR and FTIR spectroscopy, TG and DTA measurements.
Resumo:
Bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YC6H4COCH2)2TeBr2, (y=H (1a), Me (1b), MeO (1c)) can be prepared
either by direct insertion of elemental Te across CRf-Br bonds (where CRf refers to α-carbon of a functionalized organic moiety) or by the oxidative addition of bromine to (p-YC6H4COCH2)2Te (y = H (2a), Me (2b), MeO (2c)). Bis(p-substituted benzoylmethyl)tellurium dichlorides, (p-YC6H4COCH2)2TeCh (y = H (3a), Me (3b), MeO (3c)), are prepared by the reaction of the bis(p-substituted benzoylmethyl)tellurides 2a--c with S02Cl2, whereas the corresponding diiodides (p-YC6H4COCH2)2Teh (y = H
(4a), Me (4b), MeO (4c)) can be obtained by the metathetical reaction of la--c with KI, or alternatively, by the oxidative addition of
iodine to 2a--c. The reaction of 2a--c with allyl bromide affords the diorganotellurium dibrornides la--c, rather than the expected
triorganotelluronium bromides. Compounds 1-4 were characterized by elemental analyses, IR spectroscopy, 1H, l3C and 125Te
NMR spectroscopy (solution and solid-state) and in case of Ie also by X-ray crystallography. (p-MeOC6H4COCH2)2TeBr2 (1c) provides, a rare example, among organotellurium compounds, of a supramolecular architecture, where C-H-O hydrogen bonds appear to be the non-covalent intermolecular associative force that dominates the crystal packing.
Resumo:
The structure and transport of N-propyl-N-methylpyrrolidinium tetrafluoroborate (P13BF4) has been investigated over a wide temperature range in consequence to exhibiting properties suitable for potential solid-state superionic electrolyte applications. Prior to melting, the organic salt, P13BF4, transforms into a plastic crystal phase. Intrinsic conductivity in this solid, phase I (45–65 °C), is comparable to that in the melt (~10−3 S cm−1). Ionic motion and transport properties were investigated by 1H and 11B nuclear magnetic resonance (NMR) spectroscopy. Pressure-induced plastic flow in this system may accommodate volume changes in device application and to this extent, X-ray diffraction (XRD) has been used. Scanning electron microscopy (SEM) revealed complex surface morphology and lattice imperfections associated with the strong orientational disorder of the plastic state.
Resumo:
Understanding the ion transport behavior of organic ionic plastic crystals (OIPCs) is crucial for their potential application as solid electrolytes in various electrochemical devices such as lithium batteries. In the present work, the ion transport mechanism is elucidated by analyzing experimental data (single-crystal XRD, multinuclear solid-state NMR, DSC, ionic conductivity, and SEM) as well as the theoretical simulations (second moment-based solid static NMR line width simulations) for the OIPC diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate ([P1,2,2,4][PF6]). This material displays rich phase behavior and advantageous ionic conductivities, with three solid–solid phase transitions and a highly “plastic” and conductive final solid phase in which the conductivity reaches 10–3 S cm–1. The crystal structure shows unique channel-like packing of the cations, which may allow the anions to diffuse more easily than the cations at lower temperatures. The strongly phase-dependent static NMR line widths of the 1H, 19F, and 31P nuclei in this material have been well simulated by different levels of molecular motions in different phases. Thus, drawing together of the analytical and computational techniques has allowed the construction of a transport mechanism for [P1,2,2,4][PF6]. It is also anticipated that utilization of these techniques will allow a more detailed understanding of the transport mechanisms of other plastic crystal electrolyte materials.
Resumo:
The reaction of Me3SbCl2 and (Me2SnS)3 afforded the complex (Me3SbS)2Me2SnCl2 in high yields, whose molecular structure features both hypercoordinated tin and antimony atoms. In solution, (Me3SbS)2Me2SnCl2 undergoes a reversible dissociation and ligand interchange reaction to give Me3SbS, Me3SbCl2 and (Me2SnS)3.
Resumo:
A central μ3—O moiety linking two FeIII and one CeIII sites supported by two distinct heterometallic carboxylate bridging modes features in self-assembled [CeFe2(bpy)2(μ3—O)(μ—L)2(μ—LH)2(LH)(H2O)2]·0.5(bpy)·7H2O (1) (LH2 = glycolic acid), and the structure models potential bonding modes of the Rare Earth corrosion inhibitor Ce(glycolate)3 to iron or iron oxide.
Resumo:
ZnO nanoparticles doped with up to 5 at% of Co and Mn were prepared using a co-precipitation method. The location of dopant ions and the effect of doping on the photocatalytic activity were investigated. The crystal structure of nanoparticles and local atomic arrangements around dopant ions were analyzed by X-ray absorption spectroscopy. The results showed that the Co ions substituted the Zn ions in the ZnO wurtzite phase structure and induced lattice shrinkage, while Mn ions were not completely incorporated in the crystal lattice. The photocatalytic activity under simulated sunlight was characterized by the decomposition of Rhodamine B dye molecules. It was revealed that Co-doping strongly reduced the photocatalytic activity but Mn-doping showed a weaker effect on the reduction of the photoactivity.