Electrical Double Layer at a Liquid Pb–Ga Electrode in Propylene Carbonate Solutions

Differential-capacitance curves and potentials of zero charge are obtained for a liquid Pb–Ga electrode in propylene carbonate (PC) solutions of surface-inactive electrolyte LiBF₄and 0.1 M solutions of LiBr and LiI. In PC and water, double-layer parameters of Pb–Ga differ from those of Ga. The lyophilicity of Pb–Ga in respect to PC is lower than that of Ga and coincides with that of Hg.     

Nature et stabilité des complexes métalliques de cryptands dinucléants en solution II. Polythiamacrotricycles et monocycles apparentés

Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution II. Polythiamacrotricycles and Related Monocyclic Subunits The stability constants of the Cu²⁺ and Ag⁺ complexes of the cylindrical macrotricycle 1a (1,7,13,19-tetraaza 4,16-dioxa 10,22,27,32-tetrathiatricyclo[17.5.5.5]tetratriacontane) have been determined by pH-metry, as well as those of the Cu²⁺, Co²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Ag⁺ complexes of the monocyclic subunit 2a (1,7-dimethyl-1,7-diaza 4,10-dithiacyclododecane), in aqueous solutions (NaClO₄) at 25°. In the Cu(II) systems, equilibria were reached slowly, and the results established by pH-metry were confirmed by UV/VIS spectrophotometric studies. The tricycle 1a forms dinuclear cryptates with copper and silver, with overall stability constants log β₂₁₀ (Cu₂- 1a )⁴⁺ = 18.5, log β_21-2 (Cu₂- 1a (OH)₂)²⁺ = 4.8, log β₂₁₀(Ag₂- 1a )²⁺ = 23.0. Ag⁺ also forms a mononuclear (Ag- 1a )⁺ complex, with log β₁₁₀ = 13.1, but no mononuclear species were detected in the Cu- 1a system. The absorption spectra of the bis-Cu(II) complexes of 1a and 2a in aqueous medium, MeOH and propylene carbonate (PC) are given, as well as those, in MeOH and PC, of the bis-copper complexes of the related monocycles 3 and 4 (1,7-diaza-4,10,13-trithiacyclopentadecane and 1.10-diaza 4,7,13,16-tetrathiacyclooctadecane, respectively), and tricycle 5 with two benzyl groups in the lateral chains. The complexing properties of the polyoxa- and polythia macrotricycles (Parts I and II of this series) are compared to those of other bis-chelating ligands, the bicyclic bis-tren and the monocyclic bis-dien.     

High‐Rate Oxygen Reduction in Mixed Nonaqueous Electrolyte Containing Acetonitrile

A mixed nonaqueous electrolyte that contains acetonitrile and propylene carbonate (PC) was found to be suitable for a Li? O₂ battery with a metallic Li anode. Both the concentration and diffusion coefficient for the dissolved O₂ are significantly higher in the mixed electrolyte than those in the pure PC electrolyte. A powder microelectrode was used to investigate the O₂ solubility and diffusion coefficient. A 10 mA cm^?2 discharge rate on a gas‐diffusion electrode is demonstrated by using the mixed electrolyte in a Li? O₂ cell.     

Electron transfer. 102. Some oxidations by bromite (BrO2−)

Bromite, BrO₂^?, in aqueous carbonate or borate buffers (pH 9–11), reacts rapidly with H₃AsO₃, with the tartrate complex of Sb(III), and with the EDTA complexes of Sn(II) and U(IV). Each reaction yields Br^?, even when BrO₂^? is taken in excess. Reaction rates with Sb(III) and Sn(II) are independent of pH, but the acidity pattern observed with As(III) points to competing bimolecular reductions by H₂AsO₃^? and H₃AsO₃ having specific rates 3.4 and 1.2 M^?1 s^?1 (25°C, μ = 0.5M). Reduction by U(IV) is strongly inhibited by carbonate; data for carbonate buffers are in accord with the operation of two contributing reaction paths (specific rates 0.45 and 6.3 M^?1 s^?1) with the activated complex for the slower featuring one more carbonate than that for the rapid. Reactions of BrO₂^? with single electron reductants, or with reagents that can undergo both 1e and 2e changes, are generally complicated by variable induction periods, inhibition by O₂, catalyzed decomposition of BrO₂^?, or combinations of these. The much smoother reductions by 2e^? reagents must pass through OBr^?, which reacts much more rapidly than BrO₂^? in each case. An inner-sphere path, operating through an oxygen-bridged transition state and culminating in oxygen atom transfer, is proposed for the 2e reductants. Hypophosphite, despite its highly negative formal potential, is not oxidized by BrO₂^? under our conditions. Here it is likely that the substitution-inert character of the coordinatively saturated P(I) center rules out formation of the precursor required for redox.     

Conductometric study of cationic and anionic complexes in propylene carbonate

Conductivity data are used to determine thermodynamic complex formation constants for cases in which both the initial electrolyte and the complexed electrolyte form ion pairs. Using the method described in the text, the complex formation constants of Li⁺, Na⁺ and K⁺ with the crown ether 18-crown-6 and of Li⁺ with the ligand triphenylphosphine oxide in propylene carbonate have been evaluated from conductance data. The complexation of AgBr in propylene carbonate solutions of n-etrabutylammonium bromide has also been studied by the measurement of molar conductivities. The results of these studies indicate that ion pairing should not be neglected, even in high permittivity solvents such as propylene carbonate, and that the ion pair association constants correlate well with structural studies on cation-crown ether molecular conformations.     

Crystal structures,semiempirical PM3 calculations and NMR studies of trimesityllead bromide and dimesityllead dibromide

Trimesityllead bromide has been synthesized by the reaction of mesityllithium with lead(II) chloride in tetrahydrofuran (THF). As a side product, dimesityllead dibromide was formed. The structures of both compounds were determined by single-crystal X-ray diffraction analysis. Both Mes₃PbBr and Mes₂PbBr₂ were characterized by NMR (¹H, ¹³C and ²⁰⁷Pb) and other spectroscopic methods. ²⁰⁷Pb–¹H and ²⁰⁷Pb–¹³C coupling constants were determined. The experimentally obtained X-ray data were compared with those calculated at the semiempirical PM3 level.     

Synthesis and Characterization of Polynuclear Metal Complexes with Bridging Ketoiminato and Thioiminato Schiff Base Ligands

Bimetallic and trimetallic complexes of stoichiometry [M(acacen)M′Y₂], [M(sacacen)M′Y₂], and {[M(acacen)]₂M′Y₂} have been prepared by reaction of the appropriate square-planar Schiff base metal complex with various secondary metal salts in toluene and/or absolute ethanol. Systems which are reported here include those where M = Cu(II); M′ = Cu(II), Ni(II), Co(II), Mn(lI) and Zn(II); Y^? = Cl^?, Br^?, and NO₃ ^?. Trinuclear complexes have been isolated only for {[Cu(acacen)]₂M′(NO₃)₂} where M′ = Cu(lI) or Mn(II); binuclear complexes result from all other combinations. The geometry of the chelated Cu(II) ion is square-planar in the bimetallic complexes and possibly square-pyramidal in the trimetallic compounds, while that of the secondary metal ion depends on the coordination preference of M′, the nature of Y^? and whether the bridging donor atoms are oxygen or sulfur. Probable structures of the new polynuclear complexes have been deduced from spectral, conductivity and magnetic measurements.     

Thermal and Some other Properties of 2,4′-Bipyridyl Complexes with Various Salts of Lead(II)

New complexes of lead(II) with 2,4′-bipyridyl (L), with the general formulae PbL₂X₂ (where X ^?1=Cl, Br, I, NCS) and PbL₃X₂ (where (X]^?1=NO₃, ClO₄), have been prepared. Analysis of the IR spectra indicates that the 2,4′-bipyridyl is bonded to the Pb(II) ion through the least hindering N(4′). The thermal decompositions of the complexes were studied under non-isothermal conditions in air. The intermediates of decomposition at different temperatures were characterized by thermal analysis (TG and DTG), chemical analysis and X-ray diffraction. Upon heating, the complexes undergo full or partial deamination. The complexes PbL₂Cl₂ and PbL₂Br₂ decompose to volatile lead(II) halide. PbO is the final product of decomposition for the other complexes.     

Synthesis and Characterization of Transition Metal Complexes of Potassium 3‐(Pyridine‐4‐Carbonylmethyl)‐Dithiocarbazate

The preparation and characterization of some dipositive metalion complexes de rived from potassium 3‐(pyridine‐4‐carbonylmethyl)‐dithiocarbazate (PCDHK) are reported. The solid complexes of the composition ML·nH₂O (M=Cu(II), Co(II), Mn(II), Zn(II), Cd(II), Ni(II), Pb(II), L = PCD^?2, n = 0, 1, PCD^?2=PCDHK‐K⁺‐H⁺) and ML₂·2H₂O (M=UO₂(IV), L=PCDH^?1, PCDH^?1=PCDHK‐K⁺) have been characterized by elemental analyses, IR, UV, and ¹HNMR spectra. The IR spectral data indicate that PCDHK be haves as either a mononegative or binegative ligand and coordinates in a tridentate or bridging tetradentate manner.     

Kinetics of substitution reactions of transition metal complexes in 1,3-dioxolan-2-one + water and 4-methyl-1,3-dioxolan-2-one + water solvent mixtures

Summary Rate constants are reported and discussed for several substitutions of inorganic complexes in ethylene carbonate (1,3-dioxolan-2-one) + water and in propylene carbonate (4-methyl-1,3-dioxolan-2-one) + water solvent mixtures. The reactions include aquation ofcis- and oftrans-[Co(en)₂Cl₂]⁺, aquation oftrans-[Cr(OH₂)₄Cl₂]⁺, bromide substitution at [Pd(Et₄dien)Cl]⁺, thiourea substitution atcis-[Pt(4-NCpy)₂Cl₂], and aquation and cyanide attack at [Fe(X-phen)₃]²⁺ cations.     

Molar volumes and viscosities of LiClO4 and LiBr in propylene carbonate + 1,2-dimethoxyethane mixed solvents at 298.15 K

The standard partial molar volumes, viscosity B-coefficients and activation free energies of lithium salts (LiClO₄ and LiBr) in propylene carbonate (PC) with 1,2-dimethoxyethane (DME) mixed solvents have been determined as a function of the mole fraction of DME at 298.15 K from precise density and viscosity measurements. The values studied are all positive and decrease monotonously with addition of DME in the PC, which indicates that nature of the solvents plays an important role. The effects are discussed in terms of preferential solvation and packing effect in the solvation shell and electrostriction. The differences between ClO₄⁻ and Br⁻ have also been discussed.     

Solubilization of Peptides in Non-polar Organic Solvents by the Addition of Inorganic Salts: Facts and Implications

The solubility of open-chain peptide derivatives (12 examples) in non-polar, ether-type organic solvents may be greatly increased by addition of salts (LiCl, LiBr, LiI, LiBF₄, LiClO₄, NaI, MgBr₂ CaBr₂, ZnCl₂) or of titanates (Ti(OEt)₄, Ti(OCHMe₂)₄). Examples are reported (Tables 2–6) in which this solubilizing effect leads to peptide concentrations more than one-hundred-fold those in the absence of salt (cf, Boc? Ala? Gly? Gly? Gly? OH in THF from 2g·1^?1 to ≥ 300 g·1^?1 with 6 equiv. of LiCl), ¹H-NMR Spectra of one of these solutions are reported (Fig. 1). There are no indications for epimerizations of stereogenic centres on the peptide backbone. Possible applications of these solutions in peptide chemistry are discussed.     

A Vibrational Spectroscopic Study of Ion Solvation in Lithium Perchlorate/Propylene Carbonate Electrolyte

Abstract

The infrared (IR) and Raman spectra of propylene carbonate (PC) containing various concentrations of LiClO₄ have been measured and analyzed. The difference in spectra of PC with and without LiClO₄ was attributed to the interaction of the PC molecules and lithium ions. This interaction occurs mainly on the carbonyl oxygen atom of the PC molecule. The ring deformation, symmetric ring deformation, carbonyl stretching and stretching of ring oxygens for PC are sensitive to this interaction. The solvation number of Li⁺ is also calculated. On the other hand, the structure of the ClO^? ₄ is also affected by PC molecule, forming the solvent separated ion pairs.     

Cu(II) complexes of N-propyl-2-picolinamine N-oxide

Cu(II) complexes have been prepared with N-propyl-2-picolinamine N-oxide(PA) employing the perchlorate, tetrafluoroborate, nitrate, chloride and bromide salts. The following unique solids have been isolated and characterized: Cu(PA)₂X₂ (X = ClO₄^?, BF₄^? and NO₃^?) and Cu(PA)X₂ (X = Cl^?, Br^?). Characterization has been accomplished primarily by IR, electronic and ESR measurements of the solid state since considerable alteration of the complexes occurs on dissolution. PA bonds as a bidentate ligand via its N-oxide oxygen and amine nitrogen in all of the complexes. Anion coordination occurs in the halogen complexes and the nitrate ions appear to be bound to Cu(II) as monodentate ligands in Cu(PA)₂(NO₃)₂. In addition, there appears to be a rhombic distortion of the CuO₂N₂ chromophore of the perchlorate and tetrafluoroborate solids which is probably due to the steric requirements of the propyl substituents.     

Homogeneous radical polymerization of 2‐hydroxyethyl methacrylate mediated by cyclometalated cationic Ruthenium(II) complexes with PF6− and Cl− in protic media

Cationic coordinatively saturated complexes of ruthenium(II), [Ru(o‐C₆H₄‐2‐py)(phen)(MeCN)₂]⁺, bearing different counterions of PF₆^? and Cl^? have been used in the radical polymerization of 2‐hydroxyethyl methacrylate in protic media and acetone under homogeneous conditions. Exchange of PF₆^? by Cl^? increases the solubility of the complex in water. Both complexes led to the fast polymerization under mild conditions, but control was achieved only in methanol and acetone and was better for the complex with Cl^?. The polymerization accelerated in aqueous media and proceeded to a high conversion even with a monomer/catalyst = 2000/1, but without control. Polymerization mediated by complex bearing Cl^? was slower in protic solvents but faster in acetone and always resulted in lower molecular weight polymers. Thus, the nature of the anion strongly affected the catalytic activity of the complexes and may serve as way of fine‐tuning the catalytic properties. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Electrochemistry of phosphaferrocenes: II. Electrochemical behavior of 3,3′,4,4′-tetramethyl-1,1′- diphosphaferrocene bonded to M(CO)5 (M = Cr,Mo, W) fragments forming heterometallic complexes with multiple redox centers

The redox behaviour of a series of heterometallic phosphaferrocenes (hereafter refered to as I, II and III) has been studied in propylene carbonate containing 0.1 M (C₂H₅)₄N⁺ ClO₄^? both mercury and platinum electrodes.Complex I (DPF) undergoes a reversible one-electron reduction. Complexes II and III exhibit the same reversible reduction step and one (species II) or two (species III) additional irreversible reduction step(s) generating [M(CO)₅]^? anions (M = Cr, Mo, W).Oxidation of the complexes II and III indicates that fragment I is involved in the first, easiest, oxidation step, whereas further step(s) involve the M(CO)₅ moieties. The redox characteristics of the complexes I, II, III, clearly indicate the absence of cooperation between metallic centers in II and III and the very effective barrier provided by the central iron in moiety I towards mutual effects of both phospholyl rings.     

Thermal square planar-to-octahedral transformation of nickel(II) complexes containing butanediamines in a solid phase

Thermal reactions of the nickel(II) complexes, [Ni(m-bn or i-bn)₂]X₂ and [Ni(H₂O)₂(dl-bn)₂]X₂·n H₂O, where m-bn, i-bn, and dl-bn are meso-2,3-butanediamine, 2-methyl-1,2-propanediamine, and dl-2,3-butanediamine, respectively, X is Cl^?, Br^?, I^?, NO^?₃, or ClO^?₄, and n is 2 for bromide, and 0 for the others, were investigated in a solid phase before and after heating using thermal analyses (TG and DSC) and spectral and magnetic measurements. In the case of the chloride and bromide, the square planar bis(dl-bn) complexes obtained by dehydration of the respective diaqua complexes were transformed to the octahedral diacido bis(dl-bn) complexes upon further heating. The same structural transformation was observed in the thermal reactions of [Ni(m-bn)₂](NO₃)₂ and [Ni(i-bn)₂]Cl₂. It was summarily recognized that such square planar-to-octahedral transformation was favored in the order dl-bn > i-bn > m-bn complexes in the respective halides, and it was a reversible thermochromism from yellow to blue. The changes in enthalpy of the reactions were endothermic and fell in the range of about 10–20 kJ mole^?1. The possibility of such configurational change seems to be dependent mainly upon the ionic radius of the X anion, the orientation of two C-substituted methyl groups on butanediamines in the formation of the complexes, and the thermal stability of the complexes themselves.     

Synthesis, spectroscopic, and thermal studies of some Hg(II) and Cd(II) coordination compounds of N,N-bis[(E)-3-(phenylprop)-2-enylidene]propanediamine

Some new coordination compounds of cadmium(II) and mercury(II) with N,N-bis[(E)-3-(phenylprop)-2-enylidene]propanediamine (L) as a new bidentate Schiff base ligand with general formula MLX₂ (X = Cl^?, Br^?, I^?, SCN^?, and N₃ ^?) have been prepared. They were characterized by elemental analysis, FT-infrared (FT-IR) and Ultraviolet–Visible spectra, ¹H- and ¹³C-NMR spectra. The reasonable shifts of FT-IR and NMR spectral signals of the complexes with respect to the free ligand confirm well coordination of ligand and anions(X-) in inner sphere coordination mode. The thermal behavior of the complexes from room temperature to 800 °C shows weight loss by decomposition of the anions and ligand segments in the subsequent steps. The results showed that cadmium complexes have no water molecules (neither as lattice nor as coordinated water) and are decomposed in two temperature steps except about cadmium thiocyanate complex that is decomposed in three steps. Final residual contents of cadmium complexes are suggested to be cadmium oxide or sulfide. Mercury complexes were decomposed in three to four temperature steps. Mercury bromide and azide complexes leave out a little amount of mercury oxide in final, while mercury chloride, iodide, and thiocyanate complexes were found to be completely decomposed without any residual matter.     

Synthesis and X-ray crystal structures of three new terpyridine-based Pb(II) complexes,cytotoxicity studies of {[Pb(ttpy)(μ-AcO)]2}(SCN)2

Synthesis and X-ray crystal structures of three new terpyridine-based Pb(II) complexes, {[Pb(ttpy)(μ-AcO)]₂}(SCN)₂ (1) (ttpy?=?4′-tolyl-2,2′:6′,2″-terpyridine), [Pb(Clphtpy)(AcO)(ClO₄)] (2), and [Pb(Clphtpy)(SCN)₂] (3) (Clphtpy?=?4′-(4-chlorophenyl)-2,2′:6′,2″-terpyridine), are described. The synthesized materials have been characterized, also, by CHN elemental analysis, ¹H NMR, and IR spectroscopy. The structural analyses showed that, in the solid state, the coordination number of Pb(II) in 1, 2, and 3 are six, seven, and five, respectively. In the complexes, the lone-pair electrons of Pb(II) are stereochemically active and the coordination geometry of Pb(II) is hemidirected. The structures of the three complexes were compared and the effect of counter ion is described. The antibacterial activity of 1 and previously reported {[Pb(ttpy)(μ-AcO)]₂}(PF₆)₂ (1A) and {[Pb(ttpy)(μ-AcO)I]₂} (1B) were tested by minimum inhibitory concentration method to investigate the effect of counter ions on biological activity of the compounds. Also, cytotoxicity test was assessed using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay to determine the maximum non-toxic concentration of ttpy, Pb(II), and their complexes to HepG2 cells. Effective lead detoxification was observed for 1, 1A, and 1B.     

Synthesis,structural, spectroscopic,biological and catalytic activity of Co(II), Ni(II) and Cu(II) complexes of benzilic hydrazide (BH)

Co(II), Ni(II) and Cu(II) chloro complexes of benzilic hydrazide (BH) have been synthesized. Also, reaction of the ligand (BH) with several copper(II) salts, including NO₃ ^?, AcO^?, and SO₄ ^? afforded metal complexes of the general formula [CuLX(H₂O) _n ]·nH₂O, where X is the anion and n = 0, 1 or 2. The newly synthesized complexes were characterized by elemental analysis, mass spectra, molar conductance, UV–vis, IR spectra, magnetic moment, and thermal analysis (TG/DTG). The physico-chemical studies support that the ligand acts as monobasic bidentate towards metal ion through the carbonyl and hydroxyl oxygen atoms. The spectral data revealed that the geometrical structure of the complexes is square planar for Cu (II) complexes and tetrahedral for Co(II) and Ni(II) complexes. Structural parameters of the ligand and its complexes have been calculated. The ligand and its metal complexes are screened for their antimicrobial activity. The catalytic activities of the metal chelates have been studied towards the oxidative decolorization of AB25, IC and AB92 dyes using H₂O₂. The catalytic activity is strongly dependent on the type of the metal ion and the anion of Cu(II) complexes.