Cu(II), Ni(II), and Co(II) Complexes of Tetradentate Azomethine Ligands: Chemical and Electrochemical Syntheses,Crystal Structures,and Magnetic Properties

Russian Journal of Coordination Chemistry - Complexes CuL1 ? MeOH (Ia), NiL1 ? MeOH (Ib), CоL1 ? MeOH (Ic), CuL2 (IIa), NiL2 (IIb), and CоL2 (IIc) of the tetradentate...     

Highly Luminescent,Water‐Soluble Lanthanide Fluorobenzoates: Syntheses,Structures and Photophysics,Part I: Lanthanide Pentafluorobenzoates

Highly luminescent, photostable, and soluble lanthanide pentafluorobenzoates have been synthesized and thoroughly characterized, with a focus on Eu^III and Tb^III complexes as visible emitters and Nd^III, Er^III, and Yb^III complexes as infrared emitters. Investigation of the crystal structures of the complexes in powder form and as single crystals by using X‐ray diffraction revealed five different structural types, including monomeric, dimeric, and polymeric. The local structure in different solutions was studied by using X‐ray absorption spectroscopy. The photoluminescence quantum yields (PLQYs) of terbium and europium complexes were 39 and 15 %, respectively; the latter value was increased almost twice by using the heterometallic complex [Tb_0.5Eu_0.5(pfb)₃(H₂O)] (Hpfb=pentafluorobenzoic acid). Due to the effectively utilized sensitization strategy (pfb)^?→Tb→Eu, a pure europium luminescence with a PLQY of 29 % was achieved.     

XAS study of americium complexes with calixarene bearing carbamoylmethylphosphine oxide moieties

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Novel Hybrid Benzoazacrown Ligand as a Chelator for Copper and Lead Cations: What Difference Does Pyridine Make

A synthetic procedure for the synthesis of azacrown ethers with a combination of pendant arms has been developed and the synthesized ligand, characterized by various techniques, was studied. The prepared benzoazacrown ether with hybrid pendant arms and its complexes with copper and lead cations were studied in terms of biomedical applications. Similarly to a fully acetate analog, the new one binds both cations with close stability constants, despite the decrease in both constants. The calculated geometry of the complexes correlate with the data from X-ray absorption and NMR spectroscopy. Coordination of both cations differs due to the difference between the ionic radii. However, these chelation modes provide effective shielding of cations in both cases, that was shown by the stability of their complexes in the biologically relevant media towards transchelation and transmetallation.     

Analysis of the atomic structure of colloidal quantum dots of the CdSe family: X-ray spectral diagnostics and computer modelling

Colloidal quantum dots of the CdSe family have been studied by X-ray absorption near edge structure (XANES) spectroscopy and computer modelling. CdK edge XANES spectra in colloidal quantum dots based on varisized CdSe nanoparticles have been recorded. Atomic structure of CdSe particles and also CdSe particles doped by transition metal atoms Mn and Co has been modelled based on the density functional theory. The embedding of the doping atoms is shown to result in considerable changes in the local atomic structure of CdSe particles. XANES spectra have been calculated above the CdK edge in CdSe particles, above the MnK edge in CdSe:Mn particles, above the CoK edge in CdSe:Co particles. The sensitivity of XANES spectroscopy to small changes in structural parameters of the nanoparticles of CdSe family has been demonstrated that furnishes an opportunity to apply it for the verification of atomic structure parameters around positions of cadmium and doping atoms of transition metals in quantum dots based on CdSe.     

Heterometallic Na6Co3 Phenylsilsesquioxane Exhibiting Slow Dynamic Behavior in its Magnetization

A heterometallic phenylsilsesquioxane [(PhSiO_1,5)₂₂(CoO)₃(NaO_0.5)₆]?(EtOH)₆?(H₂O) 1 cage architecture of Co^II ions in a triangular topology exhibits a slow dynamic behavior in its magnetization, induced by the freezing of the spins of individual molecules.     

On the nonclassical approximation method for periodic functions by trigonometric polynomials

We study the approximation of functions by linear polynomial means of their Fourier series with a function-multiplier φ that is equal to 1 not only at zero, in contrast with classical methods of summability. The exact order of convergence to zero of the sequence $$ \mathop{\max}\limits_{{x\in \left[ {-\pi, \pi } \right]}}\left| {f(x)-\sum\limits_{{\left| k \right|\leq n}} {\varphi \left( {\frac{{k\pi }}{n}} \right){{\hat{f}}_k}{e^{ikx }}} } \right| $$ ( $ {{\hat{f}}_k} $ Fourier coefficients) as n→∞ is obtained. The answer is given in terms of the values of difference operators of a continuous function f and a special K-functional (step of $ \frac{\pi }{n} $ ). In addition, we obtain not only the sufficient conditions for φ but the necessary ones as well.     

Synthesis and investigation of the structure of nanocomposites based on nickel nanoparticles dispersed in a phthalocyanine matrix

A method based on doping of pure nickel phthalocyanine (NiPc) with a polycrystalline potassium powder at relatively low temperatures (300°C) has been proposed for the synthesis of a magnetic nanocomposite containing nickel nanoparticles stabilized in the NiPc matrix. The structural analysis of the synthesized nanoparticles and changes in the NiPc initial matrix has been performed using X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy. It has been found that, at the doping level used in this study, the synthesized samples of the K_xNiPc nanocomposites contain from 9 to 18% Ni in the form of metallic magnetic nanoparticles with an average size of more than 40 nm. It has been shown that the formation of nanoparticles is accompanied by a relative misorientation of persistent NiPc molecules with the unchanged structure of each of these molecules. The stabilization of nickel nanoparticles by the phthalocyanine matrix leads to the fact that the synthesized nanocomposites acquire time-conserving magnetic properties.     

Flow past a three-dimensional hump in the hypersonic boundary layer on a cooled body

Hypersonic gas flow past a small hump on the surface of a cold body has been investigated. The main parameters controlling the physical features of the flow in the near-wall viscous layer are determined. The solution of the boundary-value problem on a viscous sublayer along the symmetry line of flow past a wedge of finite span has been investigated numerically and the influence of the similarity parameters demonstrated.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.1, pp. 157–165, January–February, 1993.