Polynuclear cobalt(II/III) sulfites: synthesis, structure, and magnetic properties of the octanuclear cluster (NH4)11(Li subset[Co4IICo4III(SO3)16(NH3)8]).10H2O encapsulating a lithium cation

Partial oxidation of an aqueous solution of CoIICl(2).6H2O with (NH4)6[Mo7VIO24].4H2O in the presence of (NH4)2SO3.H2O and LiCl, at pH approximately 5.3, leads to isolation of the octanuclear cluster (NH4)11(Li subset[Co4IICo4III(SO3)16(NH3)8].10H2O), 1. The structure of the anion of 1 consists of a central [Co4II], almost ideal square planar unit, and a pair of symmetry-related CoIII dimers above and below the Co4II plane grafting onto the tetramer by 16 bridging sulfite groups. The [Co8(SO3)16(NH3)8]12- cluster encapsulates a lithium cation which lies at the center of the Co4II square.     

Dinuclear calcium complex with weakly NH...O hydrogen-bonded sulfonate ligands

The novel intramolecularly NH...O hydrogen-bonded Ca(II)-aryl sulfonate complex, [Ca2(SO3-2-t-BuCONHC6H4)2(H2O)4]n(2-t-BuCONHC6H4SO3)2n (1), sulfonate anion, (HNEt3)(SO3-2-t-BuCONHC6H4) (2a), (PPh4)(SO3-2-t-BuCONHC6H4) (2b), (n-Bu4N)(SO3-2-t-BuCONHC6H4) (2c), and sulfonic acid, 2-t-BuCONHC6H4SO3H (3), were synthesized. The structures of 1, 2a, and 2b depict the presence of the formation of NH...O hydrogen bonds between the amide NH and S-O oxygen for a series of compounds as determined by IR and 1H NMR analyses both in the solid state and in the solution state. Thus, the NH...O hydrogen bonds with neutral amide groups are available for investigation of the electronic state of the O- anion. The combined data from the IR and 1H NMR spectra indicate that the sulfonic acid, sulfonate anion, and Ca(II) complex have a substantially weak intramolecular NH...O hydrogen bond between the SO3 oxygen and amide NH. In the detailed comparison with the intense NH...O hydrogen bonds for the carboxylate, weak NH...O hydrogen bonds for sulfonate is due to the strong conjugation of the SO3- group with the lower nucleophilicity.     

Preparation of micrometer-sized poly(methyl methacrylate) particles with amphoteric initiator in aqueous media

A previously proposed method based on soap-free emulsion polymerization with an amphoteric initiator for producing micrometer-sized polystyrene particles was extended to application with methyl methacrylate (MMA). The aggregation and dispersion stability of polymer particles, which have ionizable groups arising from initiator radicals, can be controlled by adjusting the pH of the reaction system accompanied with the addition of ionic monomer. Polymerizations were carried out with 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate amphoteric initiator, NH(3)/NH(4)Cl pH buffer, and sodium p-styrenesulfonate anionic monomer (NaSS) in ranges of MMA concentration (0.58-2.32 kmol/m(3) H(2)O) and NH(3) concentration (2.5-20 mol/m(3) H(2)O) at fixed concentrations of 5 mol/m(3) H(2)O initiator, 10 mol/m(3) H(2)O NH(4)Cl, and 1 mol/m(3) H(2)O NaSS at 65 degrees C. The addition of NaSS during the polymerization could improve stability in dispersion of particles, which coagulated in the absence of NaSS after the disappearance of monomer drops. An increase in the monomer concentration in the present method could enlarge the particle size without lowering the monodispersity of the particle size distribution. On the other hand, an increase in NH(3) concentration decreased the particle size. The highest monodispersity of particle sizes was obtained at a NH(3) concentration of 5 mol/m(3) H(2)O, which gave an average size of 1.5 microm and a coefficient of variation of particle size distribution of 2.2% that was much smaller than the standard criterion for monodispersity, 10%.     

Undissociated versus dissociated structures for water clusters and ammonia-water clusters: (H2O)n and NH3(H2O)n-1 (n = 5, 8, 9, 21). Theoretical study

To understand the autoionization of pure water and the solvation of ammonia in water, we investigated the undissociated and dissociated (ion-pair) structures of (H2O) n and NH3(H2O)n-1 (n = 5, 8, 9, 21) using density functional theory (DFT) and second order Moller-Plesset perturbation theory (MP2). The stability, thermodynamic properties, and infrared spectra were also studied. The dissociated (ion-pair) form of the clusters tends to favor the solvent-separated ion-pair of H3O+/NH4+ and OH-. As for the NH3(H2O)20 cluster, the undissociated structure has the internal conformation, in contrast to the surface conformation for the (H2O)21 cluster, whereas the dissociated structure of NH3(H2O)20 has the surface conformation. As the cluster size of (H2O)n/NH3(H2O)n-1 increases, the difference in standard free energy between undissociated and dissociated (ion-pair) clusters is asymptotically well corroborated with the experimental free energy change at infinite dilution of H3O+/NH4+ and OH-. The predicted NH and OH stretching frequencies of the undissociated and dissociated (ion-pair) clusters are discussed.     

IR and raman spectra of two layered aluminium phosphates Co(en)3Al3P4O16.3H2O and

The FT IR and FT Raman spectra of Co(en)3Al3P4O16.3H2O (compound I) and [NH4]3[Co(NH3)6]3[Al2 (PO4)4]2.2H2O (compound II) are recorded and analysed based on the vibrations of Co(en)(3)3+, Co(NH3)(6)3+, NH4, Al-O-P, PO3, PO2 and H2O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH2 deformation Fermi resonates with its symmetric stretching vibration. The NH4 ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.     

普钙-脲-水复合肥料体系的等温溶度研究

从发展复合肥料出发,研究了ＣａＳＯ－Ｃａ（Ｈ２ＰＯ４）２Ｈ２Ｏ体系及其三元边界体系Ｃａ（Ｈ２ＰＯ４）２－ＣＯ（ＮＨ２）２－Ｈ２Ｏｄ ２５℃时的等温溶度,三元体系中形成一个新化合物Ｃａ（Ｈ２ＰＯ４）２。ＣＯ（ＮＨ２）２。四元体系溶 度图可以指导商品普钙磷肥转化为含各合复肥。     

New family of silver(I) complexes based on hydroxyl and carboxyl groups decorated arenesulfonic acid: syntheses, structures, and luminescent properties

Self-assembly of silver(I) salts and three ortho-hydroxyl and carboxyl groups decorated arenesulfonic acids affords the formation of nine silver(I)-sulfonates, (NH(4))·[Ag(HL1)(NH(3))(H(2)O)] (1), {(NH(4))·[Ag(3)(HL1)(2)(NH(3))(H(2)O)]}(n) (2), [Ag(2)(HL1)(H(2)O)(2)](n) (3), [Ag(2)(HL2)(NH(3))(2)]·H(2)O (4), [Ag(H(2)L2)(H(2)O)](n) (5), [Ag(2)(HL2)](n) (6), [Ag(3)(L3)(NH(3))(3)](n) (7), [Ag(2)(HL3)](n) (8), and [Ag(6)(L3)(2)(H(2)O)(3)](n) (9) (H(3)L1 = 2-hydroxyl-3-carboxyl-5-bromobenzenesulfonic acid, H(3)L2 = 2-hydroxyl-4-carboxylbenzenesulfonic acid, H(3)L3 = 2-hydroxyl-5-carboxylbenzenesulfonic acid), which are characterized by elemental analysis, IR, TGA, PL, and single-crystal X-ray diffraction. Complex 1 is 3-D supramolecular network extended by [Ag(HL1)(NH(3))(H(2)O)](-) anions and NH(4)(+) cations. Complex 2 exhibits 3-D host-guest framework which encapsulates ammonium cations as guests. Complex 3 presents 2-D layer structure constructed from 1-D tape of sulfonate-bridged Ag1 dimers linked by [(Ag2)(2)(COO)(2)] binuclear units. Complex 4 exhibits 3-D hydrogen-bonding host-guest network which encapsulates water molecules as guests. Complex 5 shows 3-D hybrid framework constructed from organic linker bridged 1-D Ag-O-S chains while complex 6 is 3-D pillared layered framework with the inorganic substructure constructing from the Ag2 polyhedral chains interlinked by Ag1 dimers and sulfonate tetrahedra. The hybrid 3-D framework of complex 7 is formed by L3(-) trianions bridging short trisilver(I) sticks and silver(I) chains. Complex 8 also presents 3-D pillared layered framework, and the inorganic layer substructure is formed by the sulfonate tetrahedrons bridging [(Ag1O(4))(2)(Ag2O(5))(2)](∞) motifs. Complex 9 represents the first silver-based metal-polyhedral framework containing four kinds of coordination spheres with low coordination numbers. The structural diversities and evolutions can be attributed to the synthetic methods, different ligands and coordination modes of the three functional groups, that is, sulfonate, hydroxyl and carboxyl groups. The luminescent properties of the nine complexes have also been investigated at room temperature, especially, complex 1 presents excellent blue luminescence and can sensitize Tb(III) ion to exhibit characteristic green emission.     

Keggin结构纳米硅钨酸铵的室温固相合成与物性

首次以H4SiW12O40 * 22H2O和(NH4)2C2O4 * H2O为原料,室温固相反应合成出(NH4)4SiW12O40纳米微粒;用元素分析、 FTIR确定产物的组成和结构; XRD、 TEM和BET对产物的形貌、晶粒尺寸和比表面积进行了表征; TG-DTA确定了产物的稳定温区.结果表明,产物为纳米粒子,平均粒径为60 nm,比表面积为108.7 m2/g,在430℃以下具有良好的热稳定性.在固相反应中,研磨和放热反应热效应能加快反应物扩散速率和生成物成核速率,使产物粒径减小;反应物含有结晶水和生成物H2C2O4 * 2H2O,对形成小粒径的(NH4)4SiW12O40纳米粒子起关键作用.     

A theoretical ab initio study on the H(2)NO + O(3) reaction

The deviation of the NH(2) pseudo-first-order decay Arrhenius plots of the NH(2) + O(3) reaction at high ozone pressures measured by experimentalists, has been attributed to the regeneration of NH(2) radicals due to the subsequent reactions of the products of this reaction with ozone. Although these products have not yet been characterized experimentally, the radical H(2)NO has been postulated, because it can regenerate NH(2) radicals through the reactions: H(2)NO + O(3) --> NH(2) + O(2) and H(2)NO + O(3) --> HNO + OH + O(2). With the purpose of providing a reasonable explanation from a theoretical point of view to the kinetic observed behaviour of the NH(2) + O(3) system, we have carried ab initio electronic structure calculations on both H(2)NO + O(3) possible reactions. The results obtained in this article, however, predict that of both reactions proposed, only the H(2)NO + O(3) --> NH(2) + O(2) reaction would regenerate indeed NH(2) radicals, explaining thus the deviation of the NH(2) pseudo-first-order decay observed experimentally.     

Structural rearrangements and magic numbers in reactions between pyridine-containing water clusters and ammonia

Molecular cluster ions H(+)(H(2)O)(n), H(+)(pyridine)(H(2)O)(n), H(+)(pyridine)(2)(H(2)O)(n), and H(+)(NH(3))(pyridine)(H(2)O)(n) (n = 16-27) and their reactions with ammonia have been studied experimentally using a quadrupole-time-of-flight mass spectrometer. Abundance spectra, evaporation spectra, and reaction branching ratios display magic numbers for H(+)(NH(3))(pyridine)(H(2)O)(n) and H(+)(NH(3))(pyridine)(2)(H(2)O)(n) at n = 18, 20, and 27. The reactions between H(+)(pyridine)(m)(H(2)O)(n) and ammonia all seem to involve intracluster proton transfer to ammonia, thus giving clusters of high stability as evident from the loss of several water molecules from the reacting cluster. The pattern of the observed magic numbers suggest that H(+)(NH(3))(pyridine)(H(2)O)(n) have structures consisting of a NH(4)(+)(H(2)O)(n) core with the pyridine molecule hydrogen-bonded to the surface of the core. This is consistent with the results of high-level ab initio calculations of small protonated pyridine/ammonia/water clusters.     

钾镁氯化物(硫酸盐)与脲、水体系的溶度研究

报导了KCl-MgCl2-CO(NH2)2-H2O和K2SO4-MgSO4-CO（NH2）2-H2O两个四元体系在25℃时的溶度及其饱和溶液的折光率、密度，相应的溶度图和组成-折光率、组成-密度图．前一体系中形成3个三元化合物：MgCl2·4CO（NH2）2·2H2O、MgCl2·CO（NH2）2·4H2O和KCl·MgCl2·6H2O溶度盐份图由9支共饱线、4个四元无变点组成．四元体系的水量图、性质-组成图有类似的变化．后一体系中有2个异成份溶解化合物MgSO4·CO（NH2）2·2H2O和K2SO4·MgSO4·6H2O形成，溶度等温图由7支双饱溶度线、3个四元无变点组成．对两个体系相图的相似性和差异点进行了讨论．     

Tetra- to dodecanuclear oxomolybdate complexes with functionalized bisphosphonate ligands: activity in killing tumor cells

We report the synthesis and characterization of five novel Mo-containing polyoxometalate (POM) bisphosphonate complexes with nuclearities ranging from 4 to 12 and with fully reduced, fully oxidized, or mixed-valent (Mo(V), Mo(VI)) molybdenum, in which the bisphosphonates bind to the POM cluster through their two phosphonate groups and a deprotonated 1-OH group. The compounds were synthesized in water by treating [Mo(V)(2)O(4)(H(2)O)(6)](2+) or [Mo(VI)O(4)](2-) with H(2)O(3)PC(C(3)H(6)NH(2))OPO(3)H(2) (alendronic acid) or its aminophenol derivative, and were characterized by single-crystal X-ray diffraction and (31)P NMR spectroscopy. (NH(4))(6)[(Mo(V)(2)O(4))(Mo(VI)(2)O(6))(2)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·12H(2)O (1) is an insoluble mixed-valent species. [(C(2)H(5))(2)NH(2)](4)[Mo(V)(4)O(8)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·6H(2)O (2) and [(C(2)H(5))(2)NH(2)](6)[Mo(V)(4)O(8)(O(3)PC(C(10)H(14)NO)OPO(3))(2)]·18H(2)O (4) contain similar tetranuclear reduced frameworks. Li(8)[(Mo(V)(2)O(4)(H(2)O))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·45H(2)O (3) and Na(2)Rb(6)[(Mo(VI)(3)O(8))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·26H(2)O (5) are alkali metal salts of fully reduced octanuclear and fully oxidized dodecanuclear POMs, respectively. The activities of 2-5 (which are water-soluble) against three human tumor cell lines were investigated in vitro. Although 2-4 have weak but measurable activity, 5 has IC(50) values of about 10 μM, which is about four times the activity of the parent alendronate molecule on a per-alendronate basis, which opens up the possibility of developing novel drug leads based on Mo bisphosphonate clusters.     

The effect of basis set superposition error on the convergence of intermolecular interaction energies for deprotonated complexes

The intermolecular interaction energies of the deprotonated hydrogen-bonded complexes F(-)(HF), F(-)(H(2)O), F(-)(NH(3)), Cl(-)(HF), SH(-)(HF), H(2)P(-)(HF), OH(-)(H(2)O), OH(-)(H(2)O)(2), OH(-)(NH(3)), Cl(-)(H(2)O), SH(-)(H(2)O), H(2)P(-)(H(2)O), Cl(-)(NH(3)), SH(-)(NH(3)), H(2)P(-)(NH(3)), Cl(-)(HCl), Cl(-)(H(2)S), Cl(-)(PH(3)), SH(-)(H(2)S), SH(-)(PH(3)), and H(2)P(-)(PH(3)) were calculated with correlation consistent basis sets at the MP2, MP4, QCISD(T), and CCSD(T) levels. When the basis set is smaller, the counterpoise-uncorrected intermolecular interaction energies are closer to the complete basis set limit than the counterpoise-corrected intermolecular interaction energies. The counterpoise-uncorrected intermolecular interaction energies obtained at the MP2/aug-cc-pVDZ level of theory are close to the interaction energies obtained at the extrapolated complete basis set limit in most of the complexes. Also, we investigate the accuracy of the other levels.     

Isotope exchange and structural rearrangements in reactions between size-selected ionic water clusters, H3O(+)(H2O)(n) and NH4(+)(H2O)(n), and D2O

Hydrogen/deuterium exchange in reactions of H3O(+)(H2O)n and NH4(+)(H2O)n (1 < or = n < or = 30) with D2O has been studied experimentally at center-of-mass collisions energies of < or = 0.2 eV. For a given cluster size, the cross-sections for H3O(+)(H2O)n and NH4(+)(H2O)n are similar, indicating a structural resemblance and energetics of binding. For protonated pure water clusters, H3O(+)(H2O)n, reacting with D2O the main H/D exchange mechanism is found to be proton catalyzed. In addition the H/D scrambling becomes close to statistically randomized for the larger clusters. For NH4(+)(H2O)n clusters reacting with D2O, the main mechanism is a D2O/H2O swap reaction. The lifetimes of H3O(+)(H2O)n clusters have been estimated using RRKM theory and a plateau in lifetime vs. cluster size is found already at n = 10.     

Infrared and polarized Raman spectra of (CH3)2NH2Al(SO4)2 x 6H2O

FTIR and single crystal Raman spectra of (CH3)2NH2Al(SO4)2 x 6H2O have been recorded at 300 and 90 K and analysed. The shifting of nu1 mode to higher wavenumber and its appearance in Bg species contributing to the alpha(xz) and alpha(yz) polarizability tensor components indicate the distortion of SO4 tetrahedra. The presence of nu1 and nu2 modes in the IR spectrum and the lifting of degeneracies of nu2, nu3, and nu4 modes are attributed to the lowering of the symmetry of the SO4(2-) ion. Coincidence of the IR and Raman bands for different modes suggest that DMA+ ion is orientationally disordered. One of the H atoms of the NH2 group of the DMA+ ion forms moderate hydrogen bonds with the SO4(2-) anion. Al(H2O)6(3+) ion is also distorted in the crystal. The shifting of the stretching modes to lower wavenumbers and the bending mode to higher wavenumber suggest that H2O molecules form strong hydrogen bonds with SO4(2-) anion. The intensity enhancement and the narrowing of nu1SO4, deltaC2N and Al(H2O)6(3+) modes at 90 K confirm the settling down of the protons in the hydrogen bonds formed with H2O molecules and NH2 groups. This may be one of the reasons for the phase transition observed in the crystal.     

The double H‐atom acceptability of the P=O group in new XP(O)(NHCH2C6H4‐2‐Cl)2 phosphoramidates [X = C6H5O– and CF3C(O)NH–]: a database analysis of compounds having a P(O)(NHR) group

In the hydrogen‐bond patterns of phenyl bis(2‐chlorobenzylamido)phosphinate, C₂₀H₁₉Cl₂N₂O₂P, (I), and N,N′‐bis(2‐chlorobenzyl)‐N′′‐(2,2,2‐trifluoroacetyl)phosphoric triamide, C₁₆H₁₅Cl₂F₃N₃O₂P, (II), the O atoms of the related phosphoryl groups act as double H‐atom acceptors, so that the P=O...(H—N)₂ hydrogen bond in (I) and the P=O...(H—N_amide)₂ and C=O...H—N_C(O)NHP(O) hydrogen bonds in (II) are responsible for the aggregation of the molecules in the crystal packing. The presence of a double H‐atom acceptor centre is a result of the involvement of a greater number of H‐atom donor sites with a smaller number of H‐atom acceptor sites in the hydrogen‐bonding interactions. This article also reviews structures having a P(O)NH group, with the aim of finding similar three‐centre hydrogen bonds in the packing of phosphoramidate compounds. This analysis shows that the factors affecting the preference of the above‐mentioned O atom to act as a double H‐atom acceptor are: (i) a higher number of H‐atom donor sites relative to H‐atom acceptor centres in molecules with P(=O)(NH)₃, (N)P(=O)(NH)₂, C(=O)NHP(=O)(NH)₂ and (NH)₂P(=O)OP(=O)(NH)₂ groups, and (ii) the remarkable H‐atom acceptability of this atom relative to the other acceptor centre(s) in molecules containing an OP(=O)(NH)₂ group, with the explanation that the N atom bound to the P atom in almost all of the structures found does not take part in hydrogen bonding as an acceptor. Moreover, the differences in the H‐atom acceptability of the phosphoryl O atom relative to the O atom of the alkoxy or phenoxy groups in amidophosphoric acid esters may be illustrated by considering the molecular packing of compounds having (O)₂P(=O)(NH) and (O)P(=O)(NH)(N)groups, in which the unique N—H unit in the above‐mentioned molecules almost always selects the phosphoryl O atom as a partner in forming hydrogen‐bond interactions. The P atoms in (I) and (II) are in tetrahedral coordination environments, and the phosphoryl and carbonyl groups in (II) are anti with respect to each other (the P and C groups are separated by one N atom). In the crystal structures of (I) and (II), adjacent molecules are linked via the above‐mentioned hydrogen bonds into a linear arrangement parallel to [100] in both cases, in (I) by forming R₂²(8) rings and in (II) through a combination of R₂²(10) and R₂¹(6) rings.     

Reduction and oxidation of hydroperoxo rhodium(III) complexes by halides and hypobromous acid

Oxygen atom transfer from trans-L(H(2)O)RhOOH(2+) [L = [14]aneN(4) (L(1)), meso-Me(6)[14]aneN(4) (L(2)), and (NH(3))(4)] to iodide takes place according to the rate law -d[L(H(2)O)RhOOH(2+)]/dt = k(I)[L(H(2)O)RhOOH(2+)][I(-)][H(+)]. At 0.10 M ionic strength and 25 degrees C, the rate constant k(I)/M(-)(2) s(-)(1) has values of 8.8 x 10(3) [L = (NH(3))(4)], 536 (L(1)), and 530 (L(2)). The final products are LRh(H(2)O)(2)(3+) and I(2)/I(3)(-). The (NH(3))(4)(H(2)O)RhOOH(2+)/Br(-) reaction also exhibits mixed third-order kinetics with k(Br) approximately 1.8 M(-)(2) s(-)(1) at high concentrations of acid (close to 1 M) and bromide (close to 0.1 M) and an ionic strength of 1.0 M. Under these conditions, Br(2)/Br(3)(-) is produced in stoichiometric amounts. As the concentrations of acid and bromide decrease, the reaction begins to generate O(2) at the expense of Br(2), until the limit at which [H(+)] 2(NH(3))(4)(H(2)O)RhOH(2+) + O(2); i.e., the reaction has turned into the bromide-catalyzed disproportionation of coordinated hydroperoxide. In the proposed mechanism, the hydrolysis of the initially formed Br(2) produces HOBr, the active oxidant for the second equivalent of (NH(3))(4)(H(2)O)RhOOH(2+). The rate constant k(HOBr) for the HOBr/(NH(3))(4)(H(2)O)RhOOH(2+) reaction is 2.9 x 10(8) M(-)(1) s(-)(1).     

Stabilization of calcium- and terbium-carboxylate bonds by NH...O hydrogen bonds in a mononuclear complex: a functional model of the active site of calcium-binding proteins

Novel benzoic acid ligands with bulky amide groups at the ortho position, 2,6-(MeCONH)(2)C(6)H(3)CO(2)H (1) and 2,6-(t-BuCONH)(2)C(6)H(3)CO(2)H (2), and their tris- and tetrakis(carboxylate) complexes with Ca(II) and Tb(III) ions, (NEt(4))(2)[Ca(II)[O(2)C-2,6-(t-BuCONH)(2)C(6)H(3)](4)] (4), [Tb[O(2)C-2,6-(t-BuNHCO)(2)C(6)H(3)](3)(H(2)O)(3)]] (5), and (NMe)(4)[Tb[O(2)C-2,6-(t-BuNHCO)(2)C(6)H(3)](4)(thf)] (6), were synthesized. The formation of the NH...O hydrogen bonds between the amide NH and carboxylate for 2, (NEt(4))[2,6-(t-BuCONH)(2)C(6)H(3)CO(2)] (3), and 4 was determined by (1)H NMR spectroscopy in solution and in the solid state (CRAMPS, IR). The ligand exchange reactions were attempted between 4 and a large excess of 2,4,6- Me(3)C(6)H(3)CO(2)H in chloroform-d solution; however, exchange reaction did not take place, indicating that the Ca(II) ions bound strongly to the carboxylate in 4. The Ca(II) ion binding properties with the benzoate derivatives were also examined using Tb(III) ion as a fluorescence probe. These results indicate that the NH...O hydrogen bonding between the amide NH and the oxygen atom of the carboxylate contributes to strong Ca(II) binding and prevents the dissociation of the calcium-carboxylate bond. The X-ray structural analyses of these complexes revealed that the NH.O hydrogen-bonded carboxylate ligands prefer the chelate-type coordination and create a mononuclear [Ca(O(2)CR)(4)](2)(-) or [Tb(O(2)CR)(4)](-) core with anionic charge, which is known only in the active site of calcium-binding proteins.     

Determination of the constants of affinity of FeCl3, CuCl2, and ZnCl2 for a nitrogen-containing organosilane bonded on Al2O3-cellulose acetate hybrid material surface from ethanol solution

This work describes the preparation and characterization of a cellulose acetate fiber coated with Al(2)O(3), resulting in the organic-inorganic hybrid Cel/Al(2)O(3). Furthermore, the hybrid was modified by attaching organofunctional groups by reaction with the precursor reagents (RO)(3)Si(CH(2))(3)L (L=NH(2), NH(CH(2))(2)NH(2), NH(CH(2))(2)NH(CH(2))(2)NH(2), and N(2)C(3)H(3) (imidazole)), resulting in Cel/Al(2)O(3)/Si(CH(2))(3)NH(2) (1), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(2) (2), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(CH(2))(2)NH(2) (3), and Cel/Al(2)O(3)/Si(CH(2))(3)N(2)C(3)H(3) (4). The amounts of attached organofunctional groups were (in mmol per gram of the material) 1=1.90, 2=1.89, 3=1.66, and 4=1.35. The isotherms of adsorption of FeCl(3), CuCl(2), and ZnCl(2) by Cel/Al(2)O(3)/Si(CH(2))(3)L from ethanol solutions were obtained at 298 K. Accurate estimates of the specific sorption capacities and the heteregeneous stability constants of the immobilized metal complexes were determined with the aid of several computational procedures. It is shown that the sorptional capacities are much less than the concentrations of the attached organofunctional groups. As all sorption isotherms are fitted properly with the Langmuir isotherm equation, the effects of the energetic heterogeneity and the lateral interactions do not affect the chemisorption equilibria. The heterogeneous stability constants of the immobilized complexes are fairly high, which provides efficient removal of the metal ions from solutions by the hybrid materials.     

Infrared spectrum of NH4+(H2O): evidence for mode specific fragmentation

The gas phase infrared spectrum (3250-3810 cm-1) of the singly hydrated ammonium ion, NH4+(H2O), has been recorded by action spectroscopy of mass selected and isolated ions. The four bands obtained are assigned to N-H stretching modes and to O-H stretching modes. The N-H stretching modes observed are blueshifted with respect to the corresponding modes of the free NH4+ ion, whereas a redshift is observed with respect to the modes of the free NH3 molecule. The O-H stretching modes observed are redshifted when compared to the free H2O molecule. The asymmetric stretching modes give rise to rotationally resolved perpendicular transitions. The K-type equidistant rotational spacings of 11.1(2) cm-1 (NH4+) and 29(3) cm-1 (H2O) deviate systematically from the corresponding values of the free molecules, a fact which is rationalized in terms of a symmetric top analysis. The relative band intensities recorded compare favorably with predictions of high level ab initio calculations, except on the nu3(H2O) band for which the observed value is about 20 times weaker than the calculated one. The nu3(H2O)/nu1(H2O) intensity ratios from other published action spectra in other cationic complexes vary such that the nu3(H2O) intensities become smaller the stronger the complexes are bound. The recorded ratios vary, in particular, among the data collected from action spectra that were recorded with and without rare gas tagging. The calculated anharmonic coupling constants in NH4+(H2O) further suggest that the coupling of the nu3(H2O) and nu1(H2O) modes to other cluster modes indeed varies by orders of magnitude. These findings together render a picture of a mode specific fragmentation dynamic that modulates band intensities in action spectra with respect to absorption spectra. Additional high level electronic structure calculations at the coupled-cluster singles and doubles with a perturbative treatment of triple excitations [CCSD(T)] level of theory with large basis sets allow for the determination of an accurate binding energy and enthalpy of the NH4+(H2O) cluster. The authors' extrapolated values at the CCSD(T) complete basis set limit are De [NH4+-(H2O)]=-85.40(+/-0.24) kJ/mol and DeltaH(298 K) [NH4+-(H2O)]=-78.3(+/-0.3) kJ/mol (CC2), in which double standard deviations are indicated in parentheses.