Small-angle neutron scattering study of sodium cholate and sodium deoxycholate interacting micelles in aqueous medium

Small angle neutron scattering (SANS) measurements of D₂O solutions (0.1 M) of sodium cholate (NaC) and sodium deoxycholate (NaDC) were carried out atT= 298 K. Under compositions very much above the critical micelle concentration (CMC), the bile salt micelle size growths were monitored by adopting Hayter-Penfold type analysis of the scattering data. NaC and NaDC solutions show presence of correlation peaks atQ = 0.12 and 0.1 ?_-1 respectively. Monodisperse ellipsoids of the micelles produce best fits. For NaC and NaDC systems, aggregation number (9.0, 16.0), fraction of the free counterions per micelle (0.79, 0.62), semi-minor (8.0 ?) and semi-major axes (18.4, 31.7 ?) values for the micelles were deduced. Extent of micellar growth was studied using ESR correlation time measurements on a suitable probe incorporating NaC and NaDC micelles. The growth parameter (axial ratio) values were found to be 2.3 and 4.0 for NaC and NaDC systems respectively. The values agree with those of SANS.     

Partition coefficients of ω-phenylalkanols between water and sodium deoxycholate micelles

The partition coefficient of -phenylalkanols [C₆H₅(CH₂)_mpOH, m _p =3–6] between water and micelles of sodium deoxycholate (NaDC) has been determined by a differential spectroscopic method at 25°C. The linear dependence of thestandard free energy change of transfer calculated from the partition coefficient on the alkyl chain length of the alkanols (m _p 4) yields the standard free energy change per methylene group [G^o(CH₂)]. G^o(CH₂) value for the present system, –3.21 kJ-mol ^–1 is larger in magnitude than that for sodium dodecylsulfate (SDS)--phenylalkanol system, –2.40 kJ-mol ^–1 . The result indicates that the alkyl chain of -phenylalkanols has higher affinity to NaDC micelles than to SDS micelles although the molecular structure of NaDC is more rigid and bulkier than that of SDS and the aggregation number of micelles of the former is much smaller than that of micelles of the latter. On the basis of the linear relation between the effect of added -phenylalkanols on the critical micelle concentration of NaDC (–dC_cmc/dC_a) and the partition coefficient, it is found that the degree of ionization of NaDC micelles is not influenced by solubilization of -phenylalkanols into the micelles.     

Electron transfer. 153. Internal electron transfer to bound cobalt(III) induced by hydroxyl radical

Hydroxyl radicals, generated in aqueous solution from Fe²⁺ and H₂O₂, react with the formato, glycolato, lactato and mandelato complexes of (NH₃)₅Co^III, extracting H·, releasing CO₂ and inducing the internal reduction of Co^III to Co²⁺; decomposition of peroxynitrous acid (O=N—OOH) in the presence of these complexes also yields Co²⁺, indicating partial utilization (15% at 22°C and pH 1) of a path involving OH·.     

Preparation and structural characterization of nickel(II), cobalt(II), zinc(II) and tin(IV) complexes of the isatin Schiff bases of S-methyl and S-benzyldithiocarbazates

The molecular structures of the isatin Schiff bases of S-methyldithiocarbazate (Hisasme) and S-benzyldithiocarbazate (Hisasbz) have been determined by X-ray diffraction and their complexes of general formula [ML₂]·n(solvate) [M = Co²⁺, Ni²⁺, Zn²⁺; L = anionic forms of Hisasme or Hisasbz; solvate = DMF, DMSO; n = 1, 2] and [Sn(L)Ph₂Cl]·nMeOH (n = 0, 1) have been synthesized and characterized by a variety of physicochemical techniques and X-ray diffraction. The bis-ligand complexes, [Ni(isasbz)₂]·2DMSO and [Co(isasme)₂]·DMF have a six-coordinate, distorted octahedral geometry with the two uninegatively charged tridentate ONS ligands coordinated to the metal ions meridionally via the amide O-atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. By contrast, the crystal structure of [Zn(isasbz)₂]·2DMF shows a four-coordinate distorted tetrahedral geometry with the two Schiff bases coordinated as NS bidentate ligands via the azomethine nitrogen atoms and the thiolate sulfur atoms. Steric constraints of the rigid tridentate ligands lead to unusual ‘pseudo-coordination’ of the O-donors which occupy sites close to the metal but too distant to be considered as true coordinate bonds.The crystal structures of the tin(IV) complexes [SnLPh₂Cl]·nMeOH (L = isasme and isasbz; n = 0, 1) also show that the Schiff bases act as monoanionic bidentate NS chelating agents coordinating the tin(IV) ion via the azomethine nitrogen atoms and the thiolate sulfur atoms, the tin atom in each complex is five-coordinate with a highly distorted geometry intermediate of square pyramidal and trigonal bipyramidal. Again Sn?O contacts are weak and do not qualify as coordinate bonds.     

The interaction of Cu2 + ions and NaDC micelles

By mixing an aqueous solution of CuCl2 with an NaDC aqueous solution of various concentration and initial molar ratio, seven coordinated samples with distinct appearances and characters were obtained. Their structures and components were investigated by FT-IR spectroscopy, EXAFS (the extended X-ray absorption fine structure), thermal analysis, X-ray diffraction, laser light scattering, TEM (transmission electron micrograph), element analysis and ICP (inductively coupled plasma) analysis. The following conclusions were given: (1) The complexes of Cu2+-NaDC with distinct appearances and properties were synthesized. (2) After Cu(DC)2 dissolved in NaDC aqueous solution, larger micelles (30-90 nm diameter) formed in the supernate, it is a mixed micelle with Cu(DC)2 and NaDC. So these micelles are a new kind of micelle containing two kinds of metal ions. This is a new result using metal ions as bridges to form micelle. (3) According to the different concentration of Cu2+ to NaDC, the complexes formed as gel or poly-crystals. Both the composition of gel complexes and the coordination structure of carboxyl groups with metal ions varied with the initial molar ratio of Cu2+ to Na+. The gel complexes exhibits the non-stoichiometric character. (4) These results are in agreement with physiological condition. All the different states such as gel, precipitate, micelles of various structures are present in bile of gallbladder. We can suggest an ideal model of the interaction between Cu2+ and bile salts in vivo.     

Extraction of heterometallic complexes of ruthenium and nonprecious metals by phosphorylmethylated calix[4]arenes from nitrate solutions

Synergetic extraction of [RuNO(NO₂)₄OH]^2? by calix[4]arene phosphine oxides (L) in the form of Ru/M heterometallic complexes was studied in the presence of nonprecious metals (M²⁺). The main extraction laws were recognized for [M(NO₃)₂L _n ] and [RuNO(NO₂)₄OH])ML _m ], where M²⁺ = Zn²⁺, Cu²⁺, Co²⁺, or Ni²⁺ and n, m = 1 or 2; extraction constants were determined for these metals. The variation row of the extraction constants with varying metal (Zn²⁺ > Cu²⁺ > Co²⁺ > Ni²⁺) coincides with the Irving-Williams row. Two or three PO groups of extractant L and the OH and NO₂ groups of the ruthenium anion are coordinated to the M²⁺ atom in Ru/M complexes. The conditions for generation of the Ru/Zn complex and its complete extraction were optimized as applied to the extraction of fission ruthenium from nitrated nitric acid and imitation solutions.     

A physicochemical study of Schiff base metal complexes derived from α-benzylmonoxime

Summary Metal complexes of general formula [M(DDE)·nH₂O]· nH₂O and [M(DDB)·nH₂O] [where M = Co^II, Ni^II, Cu^II, Pd^II and UO ₂ ²⁺ ; n = 0–4; DDE and DDB are the anion of bis(1,2-diphenyl-1-hydroxyimino-2-ethylidine)-1,2-diaminoethane and bis(l,2-diphenyl-l-hydroxy-imino-2-ethylidine)-1,4-diaminobenzene, respectively] were prepared and characterized by i.r. electromagnetic and n.m.r. spectroscopy and magnetic measurements.     

H＋对水溶液中脱氧胆酸钠聚集体的影响

运用pH滴定、傅立叶变换红外光谱、紫外可见光谱、激光光散射谱、ICP和元素分析等方法研究了H＋的加入对水溶液中脱氧胆酸钠（NaDC）聚集体的影响.结果表明,浓度大于cmc的NaDC水溶液具有一定的缓冲能力,NaDC浓度越高,缓冲能力越大;随溶液中H＋浓度的增加,首先形成质子化胶团,质子化胶团通过酸盐结构的氢键作用使NaDC初级胶团长大,形成较大的高级胶团,甚至形成凝胶体,最终形成HnNam(DC)n＋m沉淀.     

Electronic structure,geometry, and stability of organic cations,dications, and donor-acceptor complexes

Geometric, electronic, and energy characteristics of the complexes formed in the CF₄ ·nAIF₃ (n = I or 2) and CBr₄ ·nAIBr₃ (n = 1, 2, or 4) systems have been determined by the semiempirical AM I method. Besides the donor-acceptor complexes, the CBr₃ ⁺...AIBr₄ ^–, CBr₃ ⁺...Al₂Br₇ ^–, CBr2²⁺...(AlBr₄ ^–)₂, and CBr₂ ²⁺...(Al₂Br₇ ^–)₂ ionic complexes can be formed in the CBr₄ ·nAlBr₃ systems. In the cations and dications of polyhalomethanes (when Hal = Cl, Br, or l) in both the free and bound (included in ionic complexes) states, carbon atoms carry negative charges, the C-Hal bonds are substantially shortened, and the positive charges are located on one-coordinate halogen atoms. These cations and dications can be considered as halenium ions that differ from halenium salts with dicoordinate halogen atoms. In the cationic and dicationic complexes of the CBr₄ ·nAlBr₃ systems, the maximum positive charges on the Br atoms are 0.39 and 0.94, respectively. Fluorine-containing cations and dications have structures similar to those of carbenium ions, whereas in the CF₄ ·nAIF₃ systems (n = l or 2), only donor-acceptor complexes are formed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 3, pp. 554–560, March, 1996.     

The modifications of copper work function by layer-by-layer deposition of [W(CN)8] – Co bimetallic nanolayers

In the reaction of K₄[W(CN)₈] · 2H₂O and Co²⁺(aq) cations on the polycrystalline or monocrystalline [3 1 1] copper using layer-by-layer deposition, a thin film of the coordination polymer {[{Co(H₂O)₂(μ-CN)₄}₂W] · 4H₂O}_n was formed. The work function of copper and deposited on it bi-layers depended on a number of layers and the concentrations of the deposited precursors. At high complex concentrations work function reached the plateau after several deposition processes, while at low concentrations oscillations in the work function were observed when K⁺ or Co²⁺ cations were present in the outside layer. The changes of the work function were also dependent on Co²⁺ salt used (CoCl₂ · 6H₂O or Co(NO₃)₂ · 6H₂O). This was interpreted in terms of a layer structure resulting from various coordination of external anions to cobalt cations.     

Metallomesogens derived from benzoxazoles-salicylaldimine conjugates

The synthesis, characterization, and mesomorphic properties of a new series of Schiff bases 2a-h and metal complexes 1a-h-M are prepared and their mesomorphic properties studied. Two single crystallographic structures of 2d (n=12, m=1) and 1g-Pd (n=m=12) were determined by X-ray analysis. Both compounds crystallize in a triclinic space group P−1. A dimeric structure formed by intermolecular H-bonds in 2d was observed, giving nematic phase due to a better aspect ratio. The central geometry at Pd²⁺ ion is nearly perfect square plane. All Schiff bases 2a-h formed N or/and SmC phases. The formation of mesophases of complexes 1a-h-M was strongly dependent on metal ions incorporated. All Cu²⁺, Ni²⁺ and Pd²⁺ complexes exhibited N or/and SmC phase, respectively. However, Zn²⁺ and Co²⁺ complexes were not mesogenic. The lack of mesomorphism was probably attributed to a preferred tetrahedral geometry at Zn²⁺ and Co²⁺ over a square-planar geometry at Cu²⁺ and Pd²⁺.     

Layer-by-layer assembly of multilayer films of polyoxometalates and tris(phenanthrolinedione) complexes of transition metals

A series of organic-inorganic composite films were prepared by the layer-by-layer self-assembly method containing the phendione complexes of transition metals [M(phendione)₃]²⁺ (M=Fe²⁺, Co²⁺, phendione=1,10-phenanthroline-5,6-dione) and the polyoxometalates (POMs). UV-vis spectroscopy was used to follow the fabrication process of (BW₁₂/[M(phendione)₃]²⁺)_n (BW₁₂=BW₁₂O₄₀⁵⁻, M=Fe²⁺, Co²⁺) and (Co₄(PW₉)₂/[M(phendione)₃]²⁺)_n (Co₄(PW₉)₂=Co₄(H₂O)₂(PW₉O₃₄)₂¹⁰⁻, M=Fe²⁺, Co²⁺) multilayer films. Electrochemical studies on the films illustrate that the POM species exhibit well-defined redox peaks and the phendione species show pH-dependent electrochemical behavior. The photoluminescent properties were investigated to show the (BW₁₂/[Fe(phendione)₃]²⁺)_n film with low-energey red photoluminescence at 672 nm.     

pH- and metal-dependent structural diversity from mononuclear to two-dimensional polymers based on a flexible tricarboxylate ligand

Six complexes based on a flexible tripodal ligand H₃TTTA (2,2′,2″-[1,3,5-triazine-2,4,6-triyltris(thio)]tris-acetic acid) have been hydrothermally synthesized and structurally characterized. X-ray single-crystal diffractions reveal that they have rich structural chemistry: mononuclear, [Zn(HTTTA)(2,2′-bpy)(H₂O)₃]_n (1); dimeric metallamacrocycle, [Zn(HTTTA)(2,2′-bipy)(H₂O)]_n (2) and [Cd(HTTTA)(2,2′-bipy)(H₂O)·H₂O]_n (3); two-dimensional networks with binodal (3,6)-connected CdI₂ topology based on linear trinuclear M₃(μ²-CO²)₄(μ₂-CO₂)₂ SBUs (Secondary Building Units), [M₃(TTTA)₂(2,2′-bipy)₂(H₂O)_m·nH₂O]_n (M=Zn·4, m=0, n=4; Cd·5 and Mn·6, m=2; n=2). The value of pH and the metal ions has large influences on the resulting structures. The flexible tricarboxylic acid exhibits four coordination modes from monodentate to μ⁶-bridge. Fluorescence and magnetic properties of the complexes have also been investigated in details.     

Synthesis,spectroscopy and cyclic voltammetry of cobalt(III) complexes with 5-methyl-3-formylpyrazole N(4)-cyclohexylthiosemicarbazone (HMPz4Cy): X-ray crystal structure of [Co(MPz4Cy)2]Cl · 2.75H2O

The coordination behaviour of the novel ligand, HMPz4Cy, is reported, together with solid state isolation of its diamagnetic cobalt(III) complexes, [Co(MPz4Cy)₂]X · nH₂O (X = Cl, Br, NO₃, ClO₄ and BF₄). I.r. and ¹H-n.m.r. data for the free ligand and its Co^III complexes confirm that the ligand, HMPz4Cy, acts as a uninegative anion with NNS tridentate function via the pyrazolyl nitrogen (tertiary), azomethine nitrogen and thiol sulphur. Electronic spectra (both solid and solution) are commensurate with a distorted octahedral environment for the reported Co^III species. Cyclic voltammograms of Co^III complexes indicate a quasireversible Co⁺³/Co⁺² couple. X-ray crystallography of a representative species, [Co(MPz4Cy)₂]Cl · 2.75H₂O (C2, monoclinic), has shown unambiguously that the two ligands are orthogonally coordinated to the central Co^III ion with both the thiolato sulphurs and both pyrazolyl nitrogen atoms in cis positions.     

Conductivity and fluorescence studies on the micellization properties of sodium cholate and sodium deoxycholate in aqueous medium at different temperatures: Effect of selected amino acids

In order to add to the existing knowledge of aqueous solution behavior of bile salts in presence of amino acids, the micellization properties of sodium cholate (NaC) (1 to 20) mmol · kg⁻¹, and sodium deoxycholate (NaDC) (0.5 to 10) mmol · kg⁻¹ in 0.1 mol · kg⁻¹ aqueous solution of glycine, leucine, methionine, and histidine have been investigated at different temperatures (293.15 to 318.15) K at intervals of T = 5 K by using conductivity and fluorescence probe studies. The critical micelle concentration (CMC) values have been determined and elucidated in terms of hydrophobicity as well as hydrophilicity of NaC and NaDC in aqueous solution of these additives. Thermodynamic parameters of micellization viz. standard Gibbs free energy (Δ_micG^o), standard enthalpy (Δ_micH^o), and standard entropy (Δ_micS^o) have also been calculated to extract information regarding the nature of micellization of bile salts in aqueous solutions. The (enthalpy + entropy) compensation plots have been interpreted to the contribution of chemical part towards micellization or stability of the micelle formed.     

Stability constants for some divalent metal ion/crown ether complexes in methanol determined by polarography and conductometry

Stability constants in methanol at 25.0°C were evaluated for the complexes of the divalent cations Ca²⁺, Ni²⁺, Zn²⁺, Pb²⁺, Mg²⁺, Co²⁺ and Cu²⁺ with the macrocyclic polyethers 15-crown-5 (15C5), 18-crown-6 (18C6), dicyclohexyl-18-crown-6 (DC18C6) and dibenzo-24-crown-8 (DB24C8). The log K values of the 1:1 complexes were generally in the range 2.1–4.2, which is low in comparison to the values of the corresponding crown ether/alkali metal ion complexes. M₂L complexes were observed for the systems Pb²⁺/18C6, Pb²⁺/DC18C6, Ca²⁺/DC18C6 and Cu²⁺/D18C6, whereas ML₂ complexes were found for Ca²⁺/18C6 and Cu²⁺/18C6. Within the series of complexes studied, there was no clear relationship between cation diameter and hole size.     

Complexation and extraction of non-ferrous metals by calix[n]arene phosphine oxides

The extraction of non-ferrous metal (M²⁺) nitrates by the calix[4,6]arenes (L), bearing four or six phosphine oxide donor groups at the upper or at the lower rim, was quantitatively described in the form of [M_n(NO₃)_2nL] (n = 1, 2) complexes. The extraction constants (Zn²⁺ > Cu²⁺ > Co²⁺ > Ni²⁺) for the both types of L coincide with Irving-Williams sequence. Calix[4]arenes, phosphorylated at the lower (narrow) rim, provide better stability of ML complexes because of the best spatial fitting of M²⁺ by the donor groups. For the upper (wide) rim phosphorylated calix[4]arenes M₂L and ML₂ complexes are more stable. Unusual zwitterionic [Co₂(NO₃)₄L] complex of the lower rim tetraphosphorylated calix[4]arene 1 was determined by X-ray structural analysis.     

Lanthanide Complexes with N,N′-Bis(2- hydroxybenzylidene)-2-hydroxyphenylmethanediamine

Complexes of lanthanides with N,N-bis(2-hydroxybenzylidene)-2-hydroxyphenylmethanediamine (H₃L) were synthesized and investigated by the elemental, IR, magnetochemical, and thermogravimetric methods. Using the data obtained, they were found to have compositions Ln₂L₂ · nH₂O and La₂L₂ · MCl₂ · 4H₂O (Ln = La³⁺, Pr³⁺, Nd³⁺, Dy³⁺, Er³⁺; M = Cu²⁺, Co²⁺, Ni²⁺; n = 4, 6). Suggestions on their structures were made. In the interval of 20–140°C, these complexes were shown to be high-resistance semiconductors.     

Rational synthesis of hexanuclear metallacycles by alkylation reactions of an S-bridged CoIIIPdIICoIII trinuclear complex containing non-binding thiolato groups

The reaction of an S-bridged Co^IIIPd^IICo^III trinuclear complex containing two non-bridging thiolato groups, [Pd{Co(aet)₃}₂]²⁺ (aet = 2-aminoethanethiolate), with o-dibromoxylene (o-xylBr₂) in water produced a cyclic Co^III₄Pd^II₂ hexanuclear complex, [{Co₂Pd(aet)₄}₂(o-L)₂]⁸⁺ ([1]⁸⁺; o-L = o-bis(2-aminoethylthiomethyl)benzene), in which two Co^IIIPd^IICo^III trinuclear units are linked by two o-xyl²⁺ moieties through C–S bonds. A similar cyclic Co^III₄Pd^II₂ complex, [{Co₂Pd(aet)₄}₂(m-L)₂]⁸⁺ ([2]⁸⁺; m-L = m-bis(2-aminoethylthiomethyl)benzene), bearing a relatively large cavity that accommodates water molecule(s), was synthesized by the reaction of [Pd{Co(aet)₃}₂]²⁺ with m-dibromoxylene (m-xylBr₂) in water. While [1]⁸⁺ afforded only the racemic (Δ₄/Λ₄) isomer, both the racemic ([2a]⁸⁺; Δ₄/Λ₄) and the meso ([2b]⁸⁺; Δ₂Λ₂) isomers were formed for [2]⁸⁺. In addition, the meso [2b]⁸⁺ was found to exist as a mixture of two diastereomers, (Δ_S)₂(Λ_R)₂ and (Δ_SΔ_R)(Λ_RΛ_S), which arise from the difference in chiral configurations (R and S) of asymmetric sulfide S atoms, while the racemic [1]⁸⁺ and [2a]⁸⁺ existed as a pair of enantiomers, (Δ_S)₄ and(Λ_R)₄, which were optically resolved. The complexes obtained were characterized on the basis of electronic absorption, CD, and NMR spectroscopies, along with single crystal X-ray analyses.     

Metallkomplexe der Phosphinsäuren. XVII. Untersuchungen zur Oligomerisation von NiII- und CoII-Komplexen bifunktioneller Dithiophosphinsäuren HS(S)P(R)-R′-(R)P(S)SH [2]

Metal Complexes of Phosphinic Acids. XVII. Investigations on the Oligomerisation of Ni^II and Co^II Complexes of Bifunctional Dithiophosphinic Acids Alkali or ammonium salts of bifunctional dithiophosphinic acids react with Ni²⁺ or Co²⁺ to give complexes [S₂P(R)? (CH₂)_n? (R)PS₂M]_m or _x (R = 4-methoxyphenyl; M = Ni²⁺, Co²⁺; n = 4? 10) some of which are soluble in organic solvents and of low molecular weight (m), while others are insoluble (x). According to magnetic and spectroscopic measurements all of them contain planar NiS₄ or tetrahedral CoS₄ chromophors. While the insoluble compounds are regarded as coordination polymers, it is shown by osmometric measurements and by ³¹P{¹H} spectroscopy, that there exists the equilibrium monomers (ansa type) ? oligomers in solutions of the soluble complexes. The influence of n on the solubility and the equilibrium is discussed. The association can be explained by simple statistic considerations.