Ba Complex Research Articles

Synthesis, Crystal Structure and Catalytic Activity of a Novel Ba(II) Complex with Pyridine-2-Carboxaldehyde-2-Phenylacetic Acid Hydrazone Ligand

A novel Ba(II) complex, [BaL2Cl2] (1) (L = pyridine-2-carboxaldehyde-2-phenylacetic acid hydrazone), has been synthesized using BaCl2, pyridine-2-carboxaldehyde and 2-phenylacetohydrazide as raw materials. The structure of 1 has been determined by elemental analysis and X-ray single-crystal diffraction technique. X-ray structural analysis showed that the Ba(II) complex (1) crystallizes in monoclinic, space group P21/c with cell parameters: a = 12.464(3) Å, b = 13.531(3) Å, c = 8.8035(18) Å, β = 95.06(3)°. In 1, the Ba(II) atom is eight-coordinated in a distorted doubly-capped octahedral geometry through four N atoms and two O atoms from two different pyridine-2-carboxaldehyde-2-phenylacetic acid hydrazone ligands and two Cl−. The complex (1) forms a 3D network structure by the interaction of intermolecular N-H···Cl hydrogen bonds and π···π stacking of neighboring pyridine rings and benzene rings. The optimum conditions for the benzyl alcohol oxidation reaction using the Ba(II) complex as catalyst was investigated.

Ca(II), Sr(II) and Ba(II) ion interaction with the rheumatoid arthritis drug tenoxicam: Structural, thermal, and biological characterization

Recently, one of the most common conditions that manifests as joint and muscle inflammation is rheumatoid arthritis. One of the treatments for this arthritis includes non‐steroidal anti‐inflammatory drugs (NSAIDs) of the oxicam family, and the widest used drug in this family is tenoxicam (Tenox). In this study, the complexation properties of the drug Tenox with Ca(II), Sr(II) and Ba(II) ions in a (dichloromethane + water) binary solvent system are reported. The formed metal complexes were characterized structurally, thermally, and biologically. Tenox was found to act as a chelate monoanionic ligand towards all metal ions with complexation stoichiometry of 1:2 (Metal: Tenox) for Ca(II) and Sr(II) ions, and 1:1 for Ba(II) ions. The Tenox ligand behaves as a bidentate ligand when coordinated with Sr(II) or Ba(II) ions and as a tridentate ligand when coordinated with Ca(II) ions. The Sr(II) and Ba(II) complex of the Tenox ligand exhibited marked inhibitory effect on the cell growth of the C. albicans species.

Alkaline-Earth-Metal-Induced Liberation of Rare Allotropes of Elemental Silicon and Germanium from N-Heterocyclic Metallylenes.

The synthesis and striking reactivity of the unprecedented N-heterocyclic silylene and germylene ("metallylene") alkaline-earth metal (Ae) complexes of the type [(η(5)-C5Me5)2Ae←:E(N(t)BuCH)2] (3, 4, and 7-9; Ae = Ca, E = Ge 3; Ae = Sr, E = Ge 4; Ae = Sr, E = Si 7; Ae = Ba, E = Si 8; Ae = Ba, E = Ge 9) are reported. All complexes have been characterized by spectroscopic means, and their bonding situations investigated by density functional theory (DFT) methods. Single-crystal X-ray diffraction analyses of examples revealed relatively long Si-Ae and Ge-Ae distances, respectively, indicative of weak E:→Ae (E = Si, Ge) dative bonds, further supported by the calculated Wiberg bond indices , which are rather low in all cases (∼0.5). Unexpectedly, the complexes undergo facile transformation to 1,4-diazabuta-1,3-diene Ae metal complexes of the type [(η(5)-C5Me5)2Ae(κ(2)-{N(t)Bu═CHCH═N(t)Bu})] (Ae = Sr 10, Ae = Ba 11) or in the case of calcium to the dinuclear complex [(η(5)-C5Me5)2Ca←:N((t)Bu)═CHCH═((t)Bu)N:→Ca(η(5)-C5Me5)2] (12) under concomitant liberation of elemental silicon and germanium. The formation of elemental silicon and germanium is proven by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray spectroscopy. Notably, the decomposition of the Si(II)→Ba complex 8 produces allo-silicon, a rare allotropic form of elemental silicon. Similarly, the analogous Ge(II)→Ba complex 9, upon decomposition, forms tetragonal germanium, a dense and rare allotrope of elemental germanium. The energetics of this unprecedented alkaline-earth-metal-induced liberation of elemental silicon and germanium was additionally studied by DFT methods, revealing that the transformations are pronouncedly exergonic and considerably larger for the N-heterocyclic germylene complexes than those of the corresponding silicon analogues.

The aerobic respiratory chain of the acidophilic archaeon Ferroplasma acidiphilum: A membrane-bound complex oxidizing ferrous iron

The extremely acidophilic archaeon Ferroplasma acidiphilum is found in iron-rich biomining environments and is an important micro-organism in naturally occurring microbial communities in acid mine drainage. F. acidiphilum is an iron oxidizer that belongs to the order Thermoplasmatales (Euryarchaeota), which harbors the most extremely acidophilic micro-organisms known so far. At present, little is known about the nature or the structural and functional organization of the proteins in F. acidiphilum that impact the iron biogeochemical cycle. We combine here biochemical and biophysical techniques such as enzyme purification, activity measurements, proteomics and spectroscopy to characterize the iron oxidation pathway(s) in F. acidiphilum. We isolated two respiratory membrane protein complexes: a 850kDa complex containing an aa3-type cytochrome oxidase and a blue copper protein, which directly oxidizes ferrous iron and reduces molecular oxygen, and a 150kDa cytochrome ba complex likely composed of a di-heme cytochrome and a Rieske protein. We tentatively propose that both of these complexes are involved in iron oxidation respiratory chains, functioning in the so-called uphill and downhill electron flow pathways, consistent with autotrophic life. The cytochrome ba complex could possibly play a role in regenerating reducing equivalents by a reverse (‘uphill’) electron flow. This study constitutes the first detailed biochemical investigation of the metalloproteins that are potentially directly involved in iron-mediated energy conservation in a member of the acidophilic archaea of the genus Ferroplasma.

A novel BA complex network model on color template matching.

A novel BA complex network model of color space is proposed based on two fundamental rules of BA scale-free network model: growth and preferential attachment. The scale-free characteristic of color space is discovered by analyzing evolving process of template's color distribution. And then the template's BA complex network model can be used to select important color pixels which have much larger effects than other color pixels in matching process. The proposed BA complex network model of color space can be easily integrated into many traditional template matching algorithms, such as SSD based matching and SAD based matching. Experiments show the performance of color template matching results can be improved based on the proposed algorithm. To the best of our knowledge, this is the first study about how to model the color space of images using a proper complex network model and apply the complex network model to template matching.

Structural mechanisms of heavy-metal extrusion by the Cus efflux system

Resistance-nodulation-cell division (RND) superfamily efflux systems are responsible for the active transport of toxic compounds from the Gram-negative bacterial cell. These pumps typically assemble as tripartite complexes, spanning the inner and outer membranes of the cell envelope. In Escherichia coli, the CusC(F)BA complex, which exports copper(I) and silver(I) and mediates resistance to these two metal ions, is the only known RND transporter with a specificity for heavy metals. We have determined the crystal structures of both the inner membrane pump CusA and membrane fusion protein CusB, as well as the adaptor-transporter CusBA complex formed by these two efflux proteins. In addition, the crystal structures of the outer membrane channel CusC and the periplasmic metallochaperone CusF have been resolved. Based on these structures, the entire assembled model of the tripartite efflux system has been developed, and this efflux complex should be in the form of CusC3-CusB6-CusA3. It has been shown that CusA utilizes methionine clusters to bind and export Cu(I) and Ag(I). This pump is likely to undergo a conformational change, and utilize a relay network of methionine clusters as well as conserved charged residues to extrude the metal ions from the bacterial cell.

Conformations and vibrational spectroscopy of metal-ion/polylalanine complexes

The thermochemistry and structures of complexes of dialanine and trialanine with a series of singly and doubly charged metal ions have been examined by spectroscopic and computational approaches. Complexes with Li +, K +, Cs +, Ca 2+, Sr 2+ and Ba 2+ were formed by electrospray ionization, and studied by infrared multiple photon dissociation spectroscopy (IRMPD) in a Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer using irradiation in the 1000–1900 cm −1 infrared (IR) region from the FELIX free electron laser. Spectra were correlated with computed thermochemistry and simulated IR spectra from density functional (DFT) calculations of likely candidate conformations to make conformational assignments and characterize the variation of characteristic normal mode frequencies as a function of metal-ion identity. All trialanine complexes were found to have the charge-solvated (CS) form of the ligand with all three carbonyl oxygens chelating the metal. Dialanine was more varied: the Ba complex had largely the salt-bridge (SB) form, the Sr and Ca complexes showed a mixture of CS and SB, the Cs complex was CS with (OO) chelation, and the K, Na and Li complexes were CS in an undetermined mixture of (OO) and (NOO) chelation. Binding of the metal ion to the carboxyl carbonyl and to the amide carbonyl(s) (Amide I band) gave a red shift of the C O stretches, and a blue shift to the Amide II band. The frequency shifts were greater for more strongly interacting metal ions (smaller size, larger charge), and were found to be linearly proportional to the metal–ligand binding energy.

Peculiarities of cyanide binding to the ba 3-type cytochrome oxidase from the thermophilic bacterium Thermus thermophilus

Cytochrome c oxidase of the ba(3)-type from Thermus thermophilus does not interact with cyanide in the oxidized state and acquires the ability to bind heme iron ligands only upon reduction. Cyanide complexes of the reduced heme a(3) in cytochrome ba(3) and in mitochondrial aa(3)-type cytochrome oxidase are similar spectroscopically, but the a(3)(2+)-CN complex of cytochrome ba(3) is strikingly tight. Experiments have shown that the K(d) value of the cytochrome ba(3) complex with cyanide in the presence of reductants of the enzyme binuclear center does not exceed 10(-8) M, which is four to five orders of magnitude less than the K(d) of the cyanide complex of the reduced heme a(3) of mitochondrial cytochrome oxidase. The tightness of the cytochrome ba(3) complex with cyanide is mainly associated with an extremely slow rate of the ligand dissociation (k(off) < or = 10(-7) sec(-1)), while the rate of binding (k(on) ~ 10(2) M(-1).sec(-1)) is similar to the rate observed for the mitochondrial cytochrome oxidase. It is proposed that cyanide dissociation from the cytochrome ba(3) binuclear center might be hindered sterically by the presence of the second ligand molecule in the coordination sphere of Cu(B)(2+). The rate of cyanide binding with the reduced heme a(3) does not depend on pH in the neutral area, but it approaches linear dependence on H+ activity in the alkaline region. Cyanide binding appears to be controlled by protonation of an enzyme group with pK(a) = 8.75.

Cationized phenylalanine conformations characterized by IRMPD and computation for singly and doubly charged ions

Electrospray ionization produces phenylalanine (Phe) complexes of the alkali metal ion series, plus Ag(+) and Ba(2+). Infrared multiple photon dissociation (IRMPD) spectroscopy using the FELIX free electron laser light source is used to characterize the conformations of the ions, in conjunction with density functional theory (DFT) calculations giving thermochemical information and computed infrared spectra for likely candidate conformations. For complexes of small, singly charged ions (Li(+), Na(+), K(+) and Ag(+)) a single tridentate, charge-solvated conformational theme (N/O/Ring) binding amino nitrogen, carbonyl oxygen and the aromatic ring to the metal ion accounts for all the observations. The larger alkalis Rb(+) and Cs(+) show clear spectroscopic evidence of mixed populations, containing substantial fractions of both tridentate and also bidentate chelation. For Rb(+) the bidentate fraction is assigned as the (O/Ring) chelation pattern, while for Cs(+) a mixture of (O/Ring) and (O/O) chelation patterns seems likely. All of the smaller ions with high positive charge density have a clear preference for cation-π interaction with the side-chain aromatic ring, but for the larger ions Rb(+) and particularly Cs(+) this interaction becomes sufficiently weak to allow conformations having the metal ion remote from the π system. The Ba(2+) complex is unique in showing clear evidence of a major fraction of salt-bridge (zwitterionic) ions along with charge-solvated conformations. Plots of the frequency shifts of the two highly perturbed ligand vibrational modes (C[double bond, length as m-dash]O stretch and NH(2) frustrated inversion) give good linear correlations with the binding energy of the metal to the ligand.

Synthesis and Characterization of Double Hydrogen Bonded Ferroelectric Liquid Crystals Exhibiting Reentrant Smectic Ordering

A novel series of chiral hydrogen bonded liquid crystals have been isolated. Hydrogen bond was formed between chiral non mesogen ingredient levo tartaric acid and mesogenic p-n alkoxy benzoic acids. Phase diagram was constructed from the transition temperatures obtained by DSC and polarizing optical microscopic (POM) studies. Thermal and electrical properties exhibited by three complexes namely LTA+8BA, LTA+7BA and LTA+5BA were discussed. Salient feature of the present work was observation of a reentrant smectic C* ordering in LTA+8BA complex. This reentrant phenomenon was confirmed by DSC thermograms, optical textures of POM and temperature variation of capacitance and dielectric loss studies. Tilt angle was measured in Smectic C* and reentrant smectic Cr* phases. Goldstone mode which is manifestation of ferroelectric ordering was detected in smectic C* phase of these hydrogen bonded complexes. Two types of relaxation named as type I and type II were observed in smectic C* and smectic G phases of the present hydrogen bonded complexes respectively and a theoretical modeling was presented towards the origination of various types of relaxation mechanisms.

Electrodeposition of BaCO3 coatings on stainless steel substrates: Oriented growth in the presence of complexing agents

Electrodeposition of BaCO3 from aminecarboxylate stabilized-Ba(HCO3)2 baths, results in oriented crystallization when the bath conditions promote the decomposition of the Ba complex. Crystal growth is predominant along the c-crystallographic axis. The crystallites orient themselves with their c-axis normal to the substrate. The crystallites exhibit three-fold twinning (trilling) consequent to the evolution of the {110} planes as planes of reflection. Pairs of trillings are seen to grow about a four-sided polygon formed by the {010} crystal faces whose centre is a point of inversion.

Double hydrogen bonded ferroelectric liquid crystals: A study of field induced transition (FiT)

A novel series of chiral hydrogen bonded liquid crystals have been isolated. Hydrogen bond was formed between chiral nonmesogen ingredient levo tartaric acid and mesogenic p-n-alkoxybenzoic acids. Phase diagram was constructed from the transition temperatures obtained by DSC and polarizing optical microscopic (POM) studies. Thermal and electrical properties exhibited by three complexes namely LTA+8BA, LTA+7BA and LTA+5BA were discussed. Salient feature of the present work was the observation of a reentrant smectic ordering in LTA+8BA complex designated as C r ∗ phase. This reentrant phenomenon was confirmed by DSC thermograms, optical textures of POM and temperature variation of capacitance and dielectric loss studies. Tilt angle was measured in smectic C ∗ and reentrant smectic C r ∗ phases. Another interesting feature of the present investigation was the observation of a field induced transition (FiT) in the LTA+ nBA homologous series. Three threshold field values were noticed which give rise to two new phases (E 1 and E 2) induced by electric field and on further enhancement of the applied field the mesogen behaves like an optical shutter. FiT is reversible in the sense that when applied field is removed the original texture was restored.

Nickel(II)–baicalein complex modified multiwall carbon nanotube paste electrode and its electrocatalytic oxidation toward glycine

A modified electrode, nickel(II)–baicalein complex modified multiwall carbon nanotube paste electrode (Ni(II)–BA–MWCNT–PE), has been fabricated by electrodepositing Ni(II)–BA complex on the surface of MWCNT–PE in alkaline solution. The Ni(II)–BA–MWCNT–PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)–BA–carbon paste electrode (CPE). It also shows better electrocatalytic activity toward the oxidation of glycine than Ni(II)–MWCNT–PE. Kinetic parameters such as the electron transfer coefficient α, rate constant k s of the electrode reaction, the diffusion coefficient D of glycine, and the catalytic rate constant k cat of the catalytic reaction are determined. Moreover, the catalytic currents present linear dependence on the concentration of glycine from 20 μM to 1.0 mM by amperometry. The detection limit and sensitivity are 9.2 μM and 3.92 μA mM −1, respectively. The modified electrode for glycine determination is of the property of simple preparation, fast response, and good stability.

N10 deca-coordinated environment for a Ba(II) complex with tetrapyridyl pendant-armed azamacrocyclic ligand

An interesting Ba(II) complex with a tetrapyridyl pendant-armed azamacrocyclic is reported. The X-ray crystal structure shows the metal ion coordinated by the 10 nitrogen donor atoms from the ligand, six of them from the macrocyclic framework and the remaining four nitrogen atoms from the pyridinic pendant-arms. The coordination geometry around the metal can be considered as a distorted bicapped cube. To the best of our knowledge, only two N10-coordinated Ba(II) complexes have been previously reported, and only one of them is a macrocyclic Ba(II) complex.

Poly[[aqua(μ-2,2-dimethylmalonato)barium(II)] 2,2-dimethylmalonic acid solvate

In the title complex, {[Ba(C(5)H(6)O(4))(H(2)O)] x C(5)H(8)O(4)}(n), the neutral dimethylmalonic acid molecules and the dianionic (dimethylmalonato)barium metal-organic framework are linked by cocrystallization. The Ba atom, in a distorted monocapped square-antiprismatic geometry, is nine-coordinated by seven O atoms of four different dimethylmalonate groups and by two water molecules. This arrangement generates a two-dimensional layer parallel to the bc plane. Two such layers sandwich another layer composed of neutral dimethylmalonic acid molecules that are involved in intermolecular hydrogen bonds within this layer and to neighboring layers. This complex is different from the dimethylmalonate-Ba complex reported previously. The title compound displays a novel structure type and represents a new member of the substituted malonate series of alkaline earth complexes.

The cytochrome ba complex from the thermoacidophilic crenarchaeote Acidianus ambivalens is an analog of bc1 complexes

A novel cytochrome ba complex was isolated from aerobically grown cells of the thermoacidophilic archaeon Acidianus ambivalens. The complex was purified with two subunits, which are encoded by the cbsA and soxN genes. These genes are part of the pentacistronic cbsAB–soxLN–odsN locus. The spectroscopic characterization revealed the presence of three low-spin hemes, two of the b and one of the a s-type with reduction potentials of + 200, + 400 and + 160 mV, respectively. The SoxN protein is proposed to harbor the heme b of lower reduction potential and the heme a s, and CbsA the other heme b. The soxL gene encodes a Rieske protein, which was expressed in E. coli; its reduction potential was determined to be + 320 mV. Topology predictions showed that SoxN, CbsB and CbsA should contain 12, 9 and one transmembrane α-helices, respectively, with SoxN having a predicted fold very similar to those of the cytochromes b in bc 1 complexes. The presence of two quinol binding motifs was also predicted in SoxN. Based on these findings, we propose that the A. ambivalens cytochrome ba complex is analogous to the bc 1 complexes of bacteria and mitochondria, however with distinct subunits and heme types.

Superconducting properties of ErBCO films with BaMO 3 nanorods (M = Zr and Sn) by pulsed laser deposition

Ba complex oxides such as BaMO 3 (BMO, M = Zr and Sn) were incorporated into ErBa 2Cu 3O 7−δ (ErBCO) films on SrTiO 3 (STO) substrates for realizing higher critical current densities ( J c) in magnetic fields. Nanorods of BMO were formed in the ErBCO films with the rod diameter of about 10–20 nm. Crystal grain alignment of both ErBCO films with BZO and BSO were found to be worse with increasing the doping concentration of BMO into the films, resulting in critical temperature ( T c) degradation for the ErBCO films. J c of the ErBCO films were enhanced by the corporation of these BMO nanorods in the magnetic fields ( B) applied particularly parallel to the c-axis ( B// c). Additionally, it was observed that the J c values of the ErBCO films with BSO were higher than those of ErBCO films with BZO in the all measured magnetic fields ( B// c), which indicated that the BSO nanorods acted as more effective pinning centers in ErBCO films. Extremely high J c of 0.41 MA/cm 2 was performed for the ErBCO film with BSO of 4.9 mol% in the magnetic field ( B// c) of 3 T. We concluded that not only the decision of pinning materials, but also optimization of the three factors of crystallinity of the superconducting film, T c of the superconducting film, and doping concentration of the pinning materials into the superconducting film were important to realize higher J c in a magnetic field.

Supramolecular photochemical synthesis of an unsymmetrical cyclobutane

2-styrylbenzothiazole (1) and cinnamic acid (2) derivatives containing 15-crown-5 ether moieties form a supramolecular assembly in the presence of Ba(2+) cations in acetonitrile. The assembly is stabilized by hydrogen bonding between the heterocyclic N atom of 1 and the proton of the carboxylic group of 2, by sandwich Ba(2+) complex formation between the crown ether moieties of 1 and 2, and by pi-pi stacking interactions. Irradiation of solutions containing these supramolecular complexes leads to highly specific formation of an unsymmetrical cycloadduct. This investigation provides an interesting example of supramolecular control of [2 + 2]-photocyclization in solution.

Molecular sheets in the crystal structure of a Ba(II) complex with imidazole-4,5-dicarboxylate and water ligands

The structure of poly-tetraaquabis(μ-Himidazole-4,5-dicarboxylato-N,O;-O′)barium(II) dihydrate, Ba(C5H3N2O4)2(H2O)4·2H2O is built of molecular sheets in which singly-deprotonated imidazole-4,5-dicarboxylate [H(4,5-IDA)] bridges metal ions using its N, O bonding moiety and one oxygen atom of its second carboxylate group. Each barium(II) is coordinated by N, O bonding moieties of two ligands, two carboxylate oxygen atoms of two other ligands and four waters. The coordination number of Ba(II) is ten, and the coordination polyhedron contains fourteen faces. A network of hydrogen bonds is responsible for the stability of the crystal.

A National Review of Health Services for People with Intellectual Disabilities in Scotland

*Dr Martin Campbell, BA, TFQE, PhD Senior Teaching Fellow, School of Psychology, University of St. Andrews, St Andrews KY16 9JP, UK Tel: +44 (0)1334 462084 Fax: +44 (0)1334 463042 Email: mc1@st-andrews.ac.uk Dr Margaret Whoriskey, MBE, BA, M.Phil., C.Psychol., PhD Asst. Director, Joint Improvement Team, Scottish Executive, Edinburgh, UK Dr Ros Lyall MBChB, MPhil, MBA, MRCPsych. Consultant Psychiatrist, NHS Lothian, Edinburgh, UK Mr Alex Davidson BA Head of Adult Services, Social Work Resources, South Lanarkshire Council, UK Mr Michael McCue BA Complex Needs Services Manager Glasgow Learning Disability Partnership, Glasgow, UK * For Correspondence Introduction