Sulfate Oxygen Atoms Research Articles

Solvent-dependent hypsochromic shift in the imidazole based complex [Cu(µ2-SO4)(Im)4] and ameliorative effects on breast cancer-induced bone metastases associated oxidative injury in rats

A sulfate-bridged complex [Cu(µ2-SO4)(Im)4] (1) was prepared and structurally characterized, where Im: imidazole. The X-ray structure analysis reveals that 1 crystallizes in the monoclinic system with space group C2/c. The octahedral coordination around the metal center is made up of four distinct imine nitrogen atoms in the equatorial plane, and two sulfate oxygen atoms occupying the axial sites. The covalent linkage between metals via the sulfate group, forming infinite 1D zigzag chains, ensures the entanglement of the structure. These chains, in turn, are further assembled into a 2D network through NH⋯O hydrogen bonding. Thermal analyses underline the high thermal stability of our complex, which starts to decompose at 200 °C. The infrared spectrum confirms the results obtained from the crystallographic analysis. Optical studies reveal the presence of a hypsochromic effect noticed in the absorption and photoluminescence spectra. The synthesized compound was found to reduce both oxidative injury and histopathological features, which are associated with skeletal metastases as a result of malignant Walker 256/B breast cancer cells.

Crystal structure of a cadmium sulfate coordination polymer based on the 3,6-bis-(pyrimidin-2-yl)-1,4-di-hydro-1,2,4,5-tetra-zine ligand.

The polymeric title compound, poly[aqua-hemi[μ2-3,6-bis-(pyrimidin-2-yl)-1,4-di-hydro-1,2,4,5-tetra-zine](μ3-sulfato)-cadmium(II)], [Cd(SO4)(C10H8N8)0.5(H2O)] n , (I), represents an example of a three-dimensional coordination polymer resulting from the reaction of CdSO4·8/3H2O with 3,6-bis-(pyrimidin-2-yl)-1,4-di-hydro-1,2,4,5-tetra-zine (H2bmtz, C10H8N8) under hydro-thermal conditions. The CdII atom has a distorted octa-hedral coordination environment defined by two nitro-gen atoms from one H2bmtz ligand, three oxygen atoms from three different sulfate anions, and one oxygen atom from a coordinating water mol-ecule. The 1,4-di-hydro-1,2,4,5-tetra-zine ring of the H2bmtz ligand is located about an inversion center, with the NH group being equally disordered over two sites. The sulfate anion acts as a μ3-bridging ligand to connect three CdII atoms, resulting in the formation of [Cd(SO4)(H2O)] sheets propagating parallel to the bc plane. Adjacent sheets are inter-connected across the H2bmtz ligands, which coordinate the CdII atoms in a bis-bidentate coordination mode, to form a three-dimensional framework structure. The framework is further stabilized by classical O-H⋯O hydrogen bonds involving the coordinating water mol-ecules and the sulfate groups, and by N-H⋯O hydrogen bonds between the disordered tetra-zine NH groups and sulfate oxygen atom, along with C-H⋯π and π-π stacking [centroid-to-centroid separation = 3.5954 (15) Å] inter-actions between parallel pyrimidine rings of the H2bmtz ligand.

Complexes formed by the siderophore-based monosulfactam antibiotic BAL30072 and their interaction with the outer membrane receptor PiuA of P. aeruginosa.

Nuclear magnetic resonance and infrared spectroscopy have been used to investigate the formation of complexes of BAL30072 with Fe3+ and Ga3+ in solution and to collect geometrical parameters supporting reliable 3D structure models. Structural models for the ligand-metal complexes with different stoichiometries have been characterized using density functional theory calculations. Blind ensemble docking to the PiuA receptor from P. aeruginosa was performed for the different complexes to compare binding affinities and statistics of the residues most frequently contacted. When compared to analogues, BAL30072 was found to have an intrinsic propensity to form complexes with low ligand-to-metal stoichiometry. By using one of the sulfate oxygen atoms as a third donor in addition to the bidentate pyridinone moiety, BAL30072 can form a L2M complex, which was predicted to be the one with the best binding affinity to PiuA. The example of BAL30072 strongly suggests that a lower stoichiometry might be the one recognized by the receptor, so that to focus only on the highest stoichiometry might be misleading for siderophores with less than six donors.

Synthesis, Crystal Structure, Physical Properties and Theoretical Calculations of a New One-Dimensional Ni(II) Coordination Polymer Constructed by 1,10-Phenanthroline Derivative Ligand and Sulfate

A new Ni(II) coordination polymer constructed by 1,10-phenanthroline derivative 2-(2-chloro-6-fluorophenyl)-1H-imidazo[4,5-f][1, 10]phenanthroline (L) and inorganic sulfate anion, namely, [Ni(L)(SO4)(H2O)2]n (1), has been successfully synthesized under hydrothermal condition. In compound 1, each sulfate functions in bidentate bridging coordination mode and links two Ni(II) atoms to generate a one-dimensional chain structure. The adjacent chains are joined together by aromatic π–π interactions between L ligands to yield a two-dimensional supramolecular layer. The O–H···O and N–H···O hydrogen bonding interactions between sulfate oxygen atoms, coordination water molecules and nitrogen atoms of L ligands further stabilize the two-dimensional supramolecular architecture of 1. Moreover, the magnetic property of 1 was investigated. In addition, natural bond orbital analysis was performed by the B3LYP/LANL2DZ method in Gaussian 09 Program. The calculation results show the obvious covalent interaction between the coordinated atoms and Ni(II) ion.

Synthesis and Crystal Structures of Copper(II) Complexes with Schiff Base Ligands

Schiff bases containing N, O/S donor atoms and their metal complexes have received considerable attention owing to their intriguing structural motifs and industrial, antifungal, and biological applications. Recently, dinuclear copper(II) complexes, [Cu2(L)2(CH3COO)](ClO4) (L = 2benzoylpyridine S-methyldithiocarbazate) and [Cu2L2(SO4)] (L = di-2-pyridyl ketone N(4),N(4)-(butane-1,4-diyl)thiosemicarbazone) in which sulfur atom from Schiff bases ligand together with acetate or sulfate oxygen atoms bridges the two copper(II) ions, respectively, were reported. Although many metal(II)-Schiff base complexes have been reported, dinuclear Cu(II) complexes consist of Schiff base and other the second ligand, especially, dinuclear complexes linked through the other second ligand except the solvent molecule or the counter anion of metal salt as starting material have been little published. In this context, we reported dinuclear Cu(II) complexes of an acetyl pyridine based dithiocarbamate or 4-phenyl-3-thiosemicarbazide with benzilic acid (H2BA) as second ligand. For metal ions, benzilic acid can provide a variety of chelating and/or bridging coordination modes displayed by the carboxylic or hydroxy groups. Many frameworks constructed by BA or HBA with transition metal ions or rare earth ions have been reported, mainly using hydrothermal synthetic method. In this study, we extended these systems to a dinuclear compound of copper(II)-benzilate with 2-acetylpyridine/2-benzoylpyridine based benzhydrazide (Scheme 1) in order to study the crystal structure as part of our longstanding interest in synthesizing and extending the dimensionality of coordination compounds with mixed N,O/S coordination spheres. The molecular structures of 1 and 2 were determined using single crystal X-ray diffraction techniques. The crystallographic data and refinement parameters are listed in Table 1. Selected bond parameters are listed in Table 2. The molecular structure of complex 1 contains dinuclear [Cu2 (apb)2(HBA)(ClO4)] in which two enolate oxygen atoms and bidentate bridging HBA anion bridge the two copper(II) centers and lattice water molecule (Fig. 1a). Each of the two copper atoms in [Cu2(apb)2(HBA)(ClO4)] has different coordination environments. Cu1 adopts a five-coordinate square-pyramidal (τ = 0.27, the geometric parameter τ = |β − α|/60, where β and α are the two largest angles around the central atom; τ = 0 and 1 for the perfect square pyramidal and trigonal bipyramidal geometries, respectively.) with a N2O3 donor. The pyridine nitrogen (N1), the azomethine nitrogen atom (N2) and the enolate oxygen atom (O1) together with the carboxyl oxygen atom (O(3)) from HBA ligand comprise the basal plane of the square-pyramid whereas the enolate oxygen atom (O2) of another ligand occupies the apical position. The maximum displacement of them from the coordination plane is 0.005 (4) A (N2). Cu1 atom displaces 0.022(1) A out of the plane. The behavior of apb results in the formation of two five-membered rings around Cu1 atom. Two planes [Cu1−N1−C5−C6−N2 and Cu1−N2−N3−C8−O1] are nearly planar with mean deviation of 0.048(5) and 0.018(4) A, respectively, the dihedral angle between them being 2.3(1)°. The environment around Cu2 atom can be best described as a distorted octahedral geometry in a N2O4 manner. One

Location of hydrogen atoms in hydronium jarosite

Various models for the crystal structure of hydronium jarosite were determined from Rietveld refinements against neutron powder diffraction patterns collected at ambient temperature and also single-crystal X-ray diffraction data. The possibility of a lower symmetry space group for hydronium jarosite that has been suggested by the literature was investigated. It was found the space group is best described as \(R\bar{3}m\), the same for other jarosite minerals. The hydronium oxygen atom was found to occupy the \(\overline{3} m\) site (3a Wyckoff site). Inadequately refined hydronium bond angles and bond distances without the use of restraints are due to thermal motion and disorder of the hydronium hydrogen atoms across numerous orientations. However, the acquired data do not permit a precise determination of these orientations; the main feature up/down disorder of hydronium is clear. Thus, the highest symmetry model with the least disorder necessary to explain all data was chosen: The hydronium hydrogen atoms were modeled to occupy an m (18 h Wyckoff site) with 50 % fractional occupancy, leading to disorder across two orientations. A rigid body description of the hydronium ion rotated by 60° with H–O–H bond angles of 112° and O–H distances of 0.96 Å was optimal. This rigid body refinement suggests that hydrogen bonds between hydronium hydrogen atoms and basal sulfate oxygen atoms are not predominant. Instead, hydrogen bonds are formed between hydronium hydrogen atoms and hydroxyl oxygen atoms. The structure of hydronium alunite is expected to be similar given that alunite supergroup minerals are isostructural.

Binding of α-thrombin to surface-anchored platelet glycoprotein Ibα sulfotyrosines through a two-site mechanism involving exosite I

The involvement of exosite I in α-thrombin (FIIa) binding to platelet glycoprotein Ibα (GPIbα), which could influence interactions with other substrates, remains undefined. To address the problem, we generated the GPIbα amino terminal domain (GPIbα-N) fully sulfated on three tyrosine residues and solved the structure of its complex with FIIa. We found that sulfotyrosine (Tys) 278 enhances the interaction mainly by establishing contacts with exosite I. We then evaluated how substituting tyrosine with phenylalanine, which cannot be sulfated, affects FIIa binding to soluble or surface-immobilized GPIbα-N. Mutating Tyr(276), which mostly contacts exosite II residues, markedly reduced FIIa interaction with both soluble and immobilized GPIbα-N; mutating Tyr(278) or Tyr(279), which mostly contact exosite I residues, reduced FIIa complexing in solution by 0-20% but affinity for immobilized GPIbα-N 2 to 6-fold, respectively. Moreover, three exosite I ligands--aptamer HD1, hirugen, and lepirudin--did not interfere with soluble FIIa complexing to GPIbα-N, excluding that their binding caused allosteric effects influencing the interaction; nonetheless, all impaired FIIa binding to immobilized GPIbα-N and platelet GPIb nearly as much as aptamer HD22 and heparin, both exosite II ligands. Bound HD1 and hirugen alter Trp(148) orientation in a loop near exosite I preventing contacts with the sulfate oxygen atoms of Tys(279). These results support a mechanism in which binding occurs when the two exosites of one FIIa molecule independently interact with two immobilized GPIbα molecules. Through exosite engagement, GPIbα may influence FIIa-dependent processes relevant to hemostasis and thrombosis.

Novel complexes of silver(i) sulfate with 1-methylimidazole-2-thione: structures and vibrational spectroscopy

Crystallization of silver(I) sulfate with the ligand 1-methylimidazole-2-thione ('Hmimt') from aqueous solution, instead of yielding the expected 1:6 Ag(2)SO(4):Hmimt complex analogous to numerous other Ag(2)SO(4):thiourea-based ligand (1:6) complexes, has resulted in novel polymeric forms, one of unusual stoichiometry. Ag(2)SO(4):Hmimt (1:4) (x H(2)O) is of the form [...(mu-Hmimt)(2)Ag(mu-Hmimt)(2)Ag...](infinity|infinity)(SO(4)), with a one-dimensional polymeric cation. Ag(2)SO(4):Hmimt (3:8) (x 9 1/2 H(2)O) is a polymeric sheet structure containing Ag(12)(SO(4))(6)(Hmimt)(15) kernels linked by Hmimt ligands. The IR spectra of these compounds show unusually large shifts of the nu(NH) band due to the presence of N-H...O hydrogen bonding involving the N-H group of the ligand and the sulfate oxygen atoms. The complexes were also readily prepared by the solvent-assisted mechanochemical method, and the utility of this method for the preparation of deuterium-exchanged products for assistance in the assignment of the IR spectra is illustrated.

Hydrogen bond strength in some beryllium salts, BeXO 4·4H 2O and Me 2Be(XO 4) 2·2H 2O (X = S, Se; Me = K, Rb): Correlation of structural data and infrared spectra

Infrared spectra of the title compounds are presented and discussed in the regions of the uncoupled O–D stretches of matrix-isolated HDO molecules (isotopically dilute samples). The strengths of the hydrogen bonds are analyzed in terms of the respective O w⋯O bond distances, the Be–OH 2 interactions (synergetic effect), the proton acceptor capabilities of the sulfate and selenate oxygen atoms as deduced from Brown's bond valence sums of the oxygen atoms, the anti-cooperative effect (proton acceptor and proton donor competitive effect). The infrared spectroscopic experiments reveal that comparatively strong hydrogen bonds are formed in the compounds under study, analogical to other hydrated beryllium salts owing to the large ionic potential of the small Be 2+ ions. The wavenumbers of ν OD show that the water molecules in BeSO 4·4H 2O and in the double salts are strongly energetically distorted, i.e. their local symmetries deviate remarkably from the C 2 v molecular symmetry (for example, Δ ν have values of 74 and 36 cm −1 for H 2O(1) and H 2O(2) in K 2Be(SO 4) 2·2H 2O, and 119 cm −1 in BeSO 4·4H 2O). The hydrogen bonds in K 2Be(SeO 4) 2·2H 2O are stronger than those in K 2Be(SO 4) 2·2H 2O due to the stronger proton acceptor capability of the SeO 4 2− ions. The proton donor strengths of the water molecules in K 2Be(SO 4) 2·2H 2O and K 2Be(SeO 4) 2·2H 2O are greater than those of the water molecules in BeSO 4·4H 2O and BeSeO 4·4H 2O (i.e. larger deviations from Mikenda's curve) due to the different compositions of the respective beryllium tetrahedra-Be(XO 4) 2(H 2O) 2 in the double salts and Be(H 2O) 4 in the simple ones (proton donor competitive effect). The intramolecular O–H bond lengths are derived from the ν OD vs. r OH correlation curve [H.D. Lutz, C. Jung, J. Mol. Struct. 404 (1997) 63].

Surface tension reduction (STR) in aqueous solutions of anionic surfactants with cobalt(III) complexes

It has been observed that, at 25.0 ± 0.1 ° C , [Co(NH 3) 6](ClO 4) 3, [Co(en) 3](ClO 4) 3, [Co(bpy) 3](ClO 4) 3, and [Co(phen) 3](ClO 4) 3 in the regions of 1.25–5.00 mM aqueous solutions cause a significant surface tension reduction (STR) of water by the surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SBS), suggesting the formation of the 1:1 and 1:2 association complexes, {[complex] 3+(S −)} 2+ and {[complex] 3+(S −) 2} + where [complex] 3+ = [Co(NH 3) 6] 3+, [Co(en) 3] 3+, [Co(bpy) 3] 3+, or [Co(phen) 3] 3+, S − = DS − or BS −. The effect of [Co(en) 3] 3+ on STR in SDS–water system is the largest due to a strong hydrophilic interaction between amino protons of [Co(en) 3] 3+ and sulfate oxygen atoms of DS −. The effects of [Co(en) 3] 3+, [Co(bpy) 3] 3+, and [Co(phen) 3] 3+ on STR in SBS–water system are significant and almost same, meaning that the hydrophilic interaction between [Co(en) 3] 3+ and the sulfonate group is comparable to the hydrophobic interaction between [Co(bpy) 3] 3+ or [Co(phen) 3] 3+ and the phenyl group of BS −. The Co(III) complexes of 1.25–5.00 mM are precipitated as {[complex] 3+(S −) 3} at 0.0295–0.173 mM of S −. The precipitates, {[Co(bpy) 3] 3+(S −) 3} and {[Co(phen) 3] 3+(S −) 3} can be dissolved at higher molar ratio of [S −]/[complex 3+] than 3.5 for SDS and 4.0 for SBS. This observation suggests that the aggregated premicelle [Co(bpy or phen) 3] 2(DS) − 7 or aggregated premicelle [Co(bpy or phen) 3](BS) − 4 is formed.

Syntheses and Crystal Structures of Hydrated Ternary Cerium Sulfates: Mixed‐Valence K5Ce2(SO4)6×H2O and K2Ce(SO4)3×H2O.

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Syntheses and Crystal Structures of Hydrated Ternary Cerium Sulfates: Mixed‐valence K5Ce2(SO4)6·H2O and K2Ce(SO4)3·H2O

AbstractA new chemical and structural interpretation of K5Ce2(SO4)6·H2O (I) and a redetermination of the structure of K2Ce(SO4)3·H2O (II) is presented. The mixed‐valent compound I crystallizes in the space group C2/c with a = 17.7321(3), b = 7.0599(1), c = 19.4628(4) Å, β = 112.373(1)° and Z = 4. Compound I has been discussed earlier with space group Cc. In the structure of I, there are pairs of edge sharing cerium polyhedra connected by sulfate oxygen atoms in the μ3 bonding mode. These cerium dimers are linked through edge and corner sharing sulfate bridges, forming layers. The layers are joined by potassium ions which together with the water molecules are placed between the layers. No irregularity in the distribution of the CeIII and CeIV to cause the lost of a crystallographic center of symmetry was detected. We suggest that the charge exerted by the extra f1 electron for every cerium dimer is delocalized over the Ce1–O2–Ce2 moiety in a non‐bonding mode. As a result, the oxidations state of each cerium ion is a mean value between III and IV at each atomic position. Compound II crystallizes in the space group C2 with a = 20.6149(2), b = 7.0742(1), c = 17.8570(1) Å, β = 122.720(1)° and Z = 8. The hydrogen atoms have been located and the absolute structure has been established. Neither hydrogen atom positions nor anisotropic displacement parameters were given in the previous reports. In compound II, the cerium polyhedra are connected by edge and corner sharing sulfate groups forming a three‐dimensional network. This network contains Z‐shaped channels hosting the charge compensating potassium ions.

Preparation, crystal structure and infrared spectroscopy of the new compound rubidium beryllium sulfate dihydrate, Rb 2Be(SO 4) 2·2H 2O

The solubility in the three-component system Rb 2SO 4–BeSO 4–H 2O at 25 °C was studied by the method of isothermal decrease of supersaturation. A new compound, Rb 2Be(SO 4) 2·2H 2O, is formed in a wide concentration range (from solutions containing 27.49 mass% beryllium sulfate and 20.16 mass% rubidium sulfate up to solutions containing 15.08 mass% beryllium sulfate and 39.07 mass% rubidium sulfate). Rb 2Be(SO 4) 2·2H 2O crystallizes in the monoclinic space group P2 1/ c ( a = 11.371(2) Å, b = 11.858(2) Å, c = 7.431(1) Å, β = 96.33(1), V = 996.0 Å 3, Z = 4, R1 = 0.039 for 2672 F o > 4 σ( F o) and 153 variables). The crystal structure is characterized by three-membered chain fragments, composed of a central BeO 2(H 2O) 2 polyhedron sharing corners with two SO 4 tetrahedra. These bent [Be(SO 4) 2(H 2O) 2] 2− units are linked by rubidium ions and hydrogen bonds to double layers and further to a three-dimensional framework structure. Rb 2Be(SO 4) 2·2H 2O is isotypic to the respective potassium sulfate and selenate compounds. The strengths of the hydrogen bonds in the title compound as deduced from the infrared wavenumbers of the uncoupled OD stretches of matrix-isolated HDO molecules (isotopically dilute sample) are discussed in terms of the O w⋯O hydrogen bond distances, the different hydrogen bond acceptor capabilities of the sulfate oxygen atoms and the strong Be OH 2 interactions (synergetic effect). The intramolecular O H bond lengths are derived from the ν OD versus r OH correlation curve [H.D. Lutz, C. Jung, J. Mol. Struct. 404 (1997) 63].

Hydrothermal synthesis, crystal structure and thermal behaviour of the first lanthanide sulfato-squarate, La 2(H 2O) 4(SO 4) 2(C 4O 4)

A new three-dimensional lanthanum(III) sulfate squarate, La 2(H 2O) 4(SO 4) 2(C 4O 4), has been synthesized hydrothermally with squaric acid at 180 °C and its structure has been solved by single-crystal X-ray diffraction methods. A relevant feature of this new material is that it constitutes the first member of a family of hybrids based on this composition. It crystallizes in the monoclinic space group P 2 1 / n , with a = 6.5965 ( 1 ) Å , b = 10.9595 ( 3 ) Å , c = 9.6633 ( 2 ) Å , β = 96.457 ( 1 ) ° , V = 694.17 ( 3 ) Å 3 , Z = 2 . Its framework is built up from dimers of O O edged-sharing nine-coordinated LaO 7(H 2O) 2 polyhedra described as monocapped square antiprisms. The linking of the binuclear La species by sulfate groups occurs in planes parallel to ( 10 1 ¯ ) and subsequently generates inorganic layers showing cavities. The stacking of them along the a-axis generates tunnels filled with bonded water molecules and squarate moieties. The three-dimensionality is ensured by one sulfate oxygen atom and the C 4-cycles. Thus, according to this structural description, the material presents a novel 3D-type structure in the field of the mixed anionic lanthanide compounds. The thermal behavior of La 2(H 2O) 4(SO 4) 2(C 4O 4) has been investigated using TG-DTA and X-ray thermodiffractometry showing that this precursor of crystallized lanthanum oxide at 900 °C is stable up to 150 °C.

Synthesis, X-ray crystal structure and properties of a novel tetranuclear unsymmetrical (μ-SO 4) copper(II) complex: relevance to SO 2 fixation

The synthesis, by fixation of SO 2, the unusual crystal structure, and the spectral and redox properties of the new μ - SO 4 2 - compound [Cu 4(TPPNOL) 2(μ-SO 4) 2](ClO 4) 2 ( 1) [HTPPNOL ( N, N, N′-tris-(2-pyridylmethyl)-1,3-diaminopropan-2-ol)] are reported. In 1, the copper(II) ions are bridged by the alkoxo oxygen atoms of the HTPPNOL ligand and by exogenous sulfate bridges. The structure of 1 consists of a centro-symmetric tetranuclear core or a “Dimer of Dimers” complex, in which a μ-O,O′ sulfate oxygen atom is further coordinated to the copper centre of another similar dinuclear unit through a μ-O,O, sulfate bridge resulting in a tetranuclear arrangement. Thus, the dinuclear units are linked by two μ-O,O sulfate bridges. The simultaneous presence of two distinct coordination modes for the sulfate group in this structure is rare and 1 represents the first coordination compound presenting μ-O,O′ and μ-O,O type structures. The SO 2 fixation was monitored by changes in the electronic spectra which indicated the formation of the intermediate hydroxo complex [Cu 2(TPPNOL)(OH) 2] +, in basic medium, which, we propose, acts as the nucleophile in the SO 2 fixation mechanism.

Influence of the crystal field stabilization energy of metal(II) ions on the structural distortion of matrix-isolated SO 42− guest ions in selenate matrices

Infrared spectra of metal(II) selenate hydrates (MeSeO 4· nH 2O and Na 2Me(SeO 4) 2·2H 2O; n=6, 5, 4, 1; Me=Mg, Mn, Co, Ni, Cu, Zn, Cd) containing matrix-isolated SO 4 2− guest ions are reported and discussed with respect to the SO stretching modes ν 3 and ν 1. An adequate measure for the SO 4 2− guest ion distortion is the site group splitting Δ ν as (Δ ν ab and Δ ν ac in the case of a doublet and a triplet for ν 3, respectively; a, being the highest wavenumbered component of ν 3) and Δ ν max (the difference between the highest and the lowest wavenumbered SO stretching modes). It has been shown that the SO 4 2− guest ion distortion depends on both the number of the sulfate oxygen atoms involved in coordinative bonds with the metal(II) ions and the electronic configuration of the metal(II) ions, i.e. their crystal field stabilization energy (CFSE) additionally to the site symmetry and the local potential at the lattice site of the host lattice. The SO 4 2− guest ions matrix-isolated in MeSeO 4·H 2O (Me=Mn, Co, Zn) and in Na 2Me(SeO 4) 2·2H 2O (Me=Mn, Cu, Cd) exhibit three bands corresponding to the ν 3 modes as deduced from the site group analysis and Δ ν ab≅Δ ν bc. When SO 4 2− guest ions are incorporated in the triclinic Na 2Me(SeO 4) 2·2H 2O host lattices (Me=Co, Ni, Zn) the ν 3 stretching region resembles a higher local symmetry of the SO 4 2− guest ions (an approximate (A 1⊕E) splitting) than the crystallographic one (i.e. Δ ν ab>Δ ν bc instead of Δ ν ab≅Δ ν bc) and, hence, the ratio Δ ν ab/Δ ν bc has to be taken into account (the higher value of the ratio Δ ν ab/Δ ν bc, the weaker is the distortion of the SO 4 2− guest ions). The SO 4 2− guest ions incorporated in MeSeO 4· nH 2O ( n=6, 5, 4) exhibit a higher local symmetry of the guest ions than that deduced from the site group analysis (D 2d for the SO 4 2− guest ions in MeSeO 4·5H 2O, MeSeO 4·4H 2O and in the monoclinic MeSeO 4·6H 2O host lattices and close to T d in the tetragonal MeSeO 4·6H 2O host lattices). The analysis of the infrared spectra of selenate host lattices containing SO 4 2− guest ions reveals that the guest ions are stronger distorted when the adjacent metal(II) ions have CFSE≠0. These ions are more resistant to angular deformations of the MeO 6-octahedra (i.e. changes in the OMeO bond angles), thus facilitating the SO 4 2− guest ion distortion as compared to those having CFSE=0 which allow stronger angular deformations of the respective metal octahedra. Infrared spectra of kieserite-type compounds MeSeO 4·H 2O (Me=Mn, Co, Zn) containing matrix-isolated SO 4 2− guest ions and Me′ 2+ guest ions different from those of the host ions (i.e. Me′SO 4·H 2O in MeSeO 4·H 2O) are also presented and discussed (double matrix-spectroscopy).

Synthesis, crystal structures and properties of two new metal complexes of syn-2pyridinealdoxime with a “metallocrown” unit and a 1D double chain structure

Reactions of syn-2pyridinealdoxime (HL) with divalent metal salts in a mixed ethanol/acetonitrile solution resulted in two new metal complexes with different structures. The structure of the zinc complex, Zn 4(L) 4Cl 2(μ 3-OH) 2 · 4CH 3CN ( 1) features a 12-metallocrown-4 unit. The syn-2pyridinealdoxime ligand adopts a tridentate chelating and bridging coordination mode. The structure of Mn(HL)(SO 4)(H 2O) (2) contains a double chain along the b-axis, in which the Mn(II) cations are bridged by μ 3-SO 4 2− anions. The syn-2pyridinealdoxime ligand chelates with a Mn(II) ion using its two nitrogen atoms. These double chains are further interconnected into a 2D layer parallel to the ab-plane via hydrogen bonds between aqua ligands and the non-coordinated sulfate oxygen atoms. Results of magnetic measurements of complex 2 indicate that there is weak Curie–Weiss behavior with θ=−10(1) K indicating predominant antiferromagnetic interaction between the Mn(II) ions. Indication for magnetic low-dimensional magnetism could not be detected.

Structure determination from powder diffraction data of a new layered ammonium lanthanum sulfate, β-(NH4)La(SO4)2

A new variety of ammonium lanthanum sulfate, β-(NH4)La(SO4)2, was synthesized hydrothermally. The crystal structure was solved ab initio from powder diffraction data collected using a conventional X-ray source. The powder diffraction pattern was indexed by the successive dichotomy method: The symmetry is monoclinic, space group Pn, cell dimensions a=6.9365(4) Å, b=9.0055(5) Å, c=5.4541(4) Å, β=90.672(8)°, V=340.68(3) Å3 and Z=2 [M20=65, F30=124(0.0071,34)]. Direct methods were used for structure solution, and refinement of the atomic coordinates was carried out by the Rietveld method (RF=0.061, Rwp=0.099). The structure contains anionic layers built from lanthanum atoms ninefold coordinated to monodentate and bidentate sulfate oxygen atoms. Ammonium groups, which provide hydrogen bonds, are located between the layers. The crystal structure contrasts with that of the α phase, which is less dense by a factor of 4.4%.

Syntheses, crystal structures and magnetic properties of dinuclear copper(II) complexes with pyrazino[2,3-f ][4,7]phenanthroline (pap) as bridging ligand

Three dinuclear copper(II) complexes with pyrazino[2,3-f][4,7]phenanthroline (pap) as bridging ligand have been prepared; [Cu2(pap)(C2O4)2]·5H2O 1, [Cu2(pap)(H2O)7(SO4)]SO4·3H2O 2 and [Cu2(pap)(H2O)3(NO3)3]NO33. These are the first metal complexes of pap which have been characterized by X-ray crystallography and magnetic susceptibility measurements. In 1 the dinuclear complex is intercepted by a mirror plane; the bridging pap and the terminal oxalate ligands are bidentate in the equatorial plane of copper. In addition copper has weak axial interactions to oxygen atoms of oxalate in two neighbouring molecules. In 2 the two crystallograpically independent copper atoms are both six-co-ordinated with bridging pap and water molecules in equatorial positions, the axial positions being occupied by two water molecules or one water molecule and one sulfate oxygen atom, respectively. In 3 the co-ordination geometry of one copper is close to square pyramidal with pap, one nitrate oxygen atom and one water in equatorial positions; another water occupies the apical position. The description of the co-ordination sphere of the other copper is complicated by the presence of disorder in one of the co-ordinated nitrate groups. When considering only the major site of the disordered nitrate, the co-ordination geometry may in a first approximation be described as square pyramidal with a significant trigonal bipyramidal distortion. In the square pyramidal description the two pap nitrogen atoms, one water and one nitrate oxygen constitute the equatorial plane and a nitrate oxygen is situated in apical position. All the co-ordinated nitrate ions have a second weak Cu⋯O interaction. The Cu⋯Cu separations across bridging pap are 6.740 (1), 6.834 (2) and 6.808 A (3). Variable-temperature susceptibility measurements reveal Curie law behaviour with very weak intramolecular antiferromagnetic coupling in all three compounds, the relevant parameters being J = −1.4 cm−1, g = 2.06 for 1, J = −1.5 cm−1, g = 2.10 for 2, and J = −1.3 cm−1, g = 2.08 for 3 (the Hamiltonian being H = −J SA·SB).

Sulfate adsorption on a Au(111) electrode studied by AES, CEELS, LEED and cyclic voltammetry

We have studied interactions of sulfate anions with a Au(111) electrode using Auger electron spectroscopy (AES), low energy electron diffraction (LEED), core electron energy loss spectroscopy ( CEELS ), and electrochemistry, and have employed a nonstandard method of quantitative analysis by AES in which the anion coverage is determined using a thick Na 2SO 4 film as a reference. A favorable comparison of surface coverage results obtained in this manner with the radiochemical, in situ, data shows that the sulfate adsorbate formed in solution does not desorb upon exposure to ultra-high vacuum (UHV). Since the AES ratio of oxygen-to-sulfur in the sulfate adlattice is 4, and the S(LMM) Auger electron transitions and S(L 2, 3) core electron energy loss spectra show a characteristic S 6+ surface valency, our results indicate that no decomposition, e.g., dehydration, of the anion occurs in UHV. In a narrow potential range around E = 1.12 V on the potential scale in use, the adsorbate forms an ordered Au(111)( 3 × 3 ) R30° adlattice that gives rise to a clear, but diffuse LEED pattern. This structure is discussed vis-á-vis recent scanning tunneling microscopy results with the same Au(111)/solution interface. In addition to the structural considerations, our companion spectroscopic analyses suggest that surface gold electrons participate in the anion chemisorption. Namely, below 1.12 V, the down-shift in the core electron loss energy is indicative of increasing electron density on sulfur with increasing sulfate-surface bonding via a back-donation into empty electronic orbitals. Above 1.12 V, the electron loss spectra are dominated by the final state effect induced by the decrease in the number of sulfate oxygen atoms that coordinate the electrode surface.