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[en] Potassium iron(III)hexacyanoferrate(II) supported on poly metylmethacrylate has been synthesized and investigated for the strontium(II) removal from HNO3 and HCl solutions. The ion exchange material characterized by different techniques and found to be stable in 1.0-4.0 M HNO3 solutions, has been used to elaborate different parameters related to ion exchange and sorption processes involved. The data collected suggested its use to undertake removal of Sr(II) from more acidic active waste solutions. Thus the material synthesized had been adjudged to present better chances of application for Sr(II) removal as compared to other such materials. (author)
[en] The crystal structure of nitrilotris(methylenephosphonato)potassium K[μ"6-NH(CH_2PO_3)_3H_4]—a three-dimensional coordination polymer—was determined. The potassium atom is coordinated by seven oxygen atoms belonging to the six nearest ligand molecules, resulting in distorted monocapped octahedral coordination geometry. The complex contains the four-membered chelate ring K–O–P–O. The K–O chemical bond is predominantly ionic. Meanwhile, the bonds of the potassium atom with some oxygen atoms have a noticeable covalent component. In addition to coordination bonds, the molecules in the crystal packing are linked by hydrogen bonds.
[en] Two chiral K(I) complexes based on D-saccharic acid (H2sac), [K(Hsac)]n (1) and [K2(sac)]n (2) were obtained from acidic and alkaline solution. The 3D framework of 1 includes K(I) polyhedral rods and typical pairwise coaxial right- and left-handed helical chains, and displays binodal 6-connected pcu topology. 2 contains 2D polyhedral sheets consisting of left-handed helical chains, and generates 3D network with an unprecedented (7,11)-connected net. Cyclic voltammetry tests and charge-discharge tests indicate that the addition of complex 2 to the electrolyte could improve the electrochemical properties of the nickel hydroxide electrode. -- Graphical abstract: Two K(I) complexes based on D-saccharic acid (H2sac), [K(Hsac)]n (1) and [K2(sac)]n (2) were obtained and characterized. Electrochemical studies indicate the potential use of 2 in Ni-MH battery. Display Omitted Highlights: → Two novel chiral K(I) frameworks based on D-saccharic acid were obtained. → The structure of 1 includes K(I) polyhedral rods and typical helical chains. → 2 contains 2D polyhedral sheets and generates an unprecedented (7,11)-connected net. → Addition of 2 to electrolyte could improve the nickel hydroxide electrode's property.
[en] Via inelastic neutron scattering (INS) generalized phonon densities of states are obtained for C60 and superconducting A3C60 (A = K, Rb). Changes in the intramolecular modes agree with and augment recent Raman (RA), infrared (IR), and INS measurements, i.e., in the vicinity of the high-frequency modes of C60 [Hg(8), Ag(2), Hg(7)] we find a pronounced shift of about 10 meV toward smaller energy transfers upon intercalating with potassium. Separated from these vibrations by a gap are the intermolecular spectra which for the doped samples display well-defined optic modes at 11 and 14 meV due to the vibrations of Rb and K ions. Indications of a weak anomalous temperature dependence of low-energy phonons (hω < 3 meV) near Tc are observed for K3C60. 9 refs., 3 figs
[en] The structures and binding energies of several cation:ether complexes (K+:dimethyl ether, K+:dimethoxyethane, K+:12-crown-4 and K+:18-crown-6) were determined with second and fourth order perturbation theory using correlation consistent basis sets. Several of these are the largest correlated calculations yet attempted on crown ethers. The observed systematic convergence to the complete basis set limit provides a standard by which the accuracy of previous studies can be measured and facilitates the calibration of density functional methods. Recent Fouier transform ion cyclotron resonance experiments predicted K+:18-crown-6 binding energies which were significantly smaller than ab initio calculations. None of the potential sources of error examined in the present study were large enough to explain this difference. Although the 6-31+G* basis set used in an earlier theoretical study was smaller than the smallest of the correlation consistent basis sets, with suitable correction for basis set superposition error, it appears capable of yielding binding energies within several kcal/mol of the basis set limit. Perturbation theory calculations exploiting the open-quote open-quote resolution of the identity close-quote close-quote approximation were found to faithfully reproduce binding energies and conformational differences. Although the cation endash ether interaction is dominated by classical electrostatics, the accuracy of density functional techniques was found to be quite sensitive to the choice of functionals. The local density SVWN procedure performed well for binding energies and conformational differences, while underestimating K+O distances by up to 0.08 A. The gradient-corrected Becke endash Lee endash Yang endash Parr functional underestimated the K+:12c4 binding energy by 4 endash 7 kcal/mol or 15%. copyright 1996 American Institute of Physics