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Nanosized centers for mercury(II) ions adsorption on a surface of modified silica

100%
Belyakova L., Shvets O., Lyashenko D.
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EN
The present work investigates the adsorptive interactions of Hg(II) ions in aqueous medium with hydroxylated silica, aminopropylsilica and silica chemically modified by β-cyclodextrin. Batch adsorption studies were carried out with various agitation times and mercury(II) concentrations. The maximum adsorption was observed within 15–30 min of agitation. The kinetics of the interactions, tested with the model of Lagergren for pseudo-first and pseudo-second order equations, showed better agreement with first order kinetics (k1 = 3.4 ± 0.2 to 5.9 ± 0.3 min−1). The adsorption data gave good fits with Langmuir isotherms. The results have shown that β-cyclodextrin-containing adsorbent has the largest adsorption specificity to Hg(II): K L = 4125 ± 205 mmol−1. “β-cyclodextrin-NO3-” inclusion complexes with ratio 1: 1 and super molecules with composition C42H70O35 ⊎ 3 Hg(NO3)2 are formed on the surface of β-cyclodextrin-containing silica. [...]
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Self-assembled hydrogen-bonded coordination networks in two copper(II) carboxylates with 4-pyridylmethanol

100%
Maroszová J., Moncol J., Padělková Z., Sillanpää R., Lis T., Koman M.
Open Chemistry
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2011
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vol. 9
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issue 3
453-459
EN
The crystal and molecular structure of [Cu(nif)2(4-PM)2]·CH3OH (1) and [Cu(2-Clbz)2(4-PM)2(H2O)] (2), (where nif = niflumate anion, 2-Clbz = 2-chlorobenzoate anion and 4-PM is the 4-pyridylmethanol), have been determinated by X-ray crystallography. The Cu2+ cation in (1), is coordinated by two pairs of oxygen atoms from asymmetric bidentate niflumate anions and by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol ligands in trans position forming an extremely elongated bipyramid. The Cu2+ cation in (2), is coordinated by a pair of oxygen atoms from monodentate 2-chlorobenzoate anions, further by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol ligands and finally by a water oxygen atom forming a tetragonal-pyramidal coordination polyhedron. The molecules of both complexes in crystal structures are linked by O-H…O hydrogen bonds, which created a three-dimensional hydrogen-bonding networks. The Π-Π stacking interactions are also observed in crystal structures of complex 2. The spectral properties (IR and electronic spectra) of both complexes were also investigated.
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Weak sulfur-sulfur interactions between chemically-identical atoms

86%
Silaghi-Dumitrescu R., Lupan A.
Open Chemistry
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2013
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vol. 11
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issue 3
457-463
EN
Abstract Experimentally-known sulfur-sulfur distances shorter than the sum of van der Waals radii and involving two chemically-identical sulfur atoms are examined at several levels of theory (BP86/6-31G** to CCSD(T)/6-311+G**). None of the theoretical methods predict an attractive interaction from an energetic point of view, even though molecular orbitals stretching between the two sulfur atoms have been identified. Most likely, if there is indeed an attractive interaction force between chemically identical sulfur atoms, its value is comparable to the accuracy of the methods employed here - implying an attractive interaction below 1 kcal/mol. The investigation includes some simple models of 1,6,12,17-tetrathiacyclodocosa-2,4,13,15-tetrayne which was previously shown to have an S-S interaction involving two chemically-identical atoms. Attractive interactions calculated for these latter models are shown to arise from S-HC weak bonding, with the S-S interaction being again repulsive. Graphical abstract [...]
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