The effect of carbonyl carbon atom replacement in acetone molecule (ACN) by sulfur atom (DMSO): Part II. Thermodynamic functions of complex formation of crown ethers with Na<Superscript>+</Superscript> in mixed solvents

The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na⁺) in acetone–water mixtures at 298.15 K have been calculated. The equilibrium constants of B15C5/Na⁺ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by the calorimetric method. The complexes are enthalpy-stabilized but entropy-destabilized in acetone–water mixtures. The effects of hydrophobic hydration, preferential solvation of B15C5 by a molecule of water and acetone, respectively and the solvation of Na⁺ on the complex formation processes have been discussed. The calculated thermodynamic functions of B15C5/Na⁺ complex formation and the effect of benzene ring on the complex formation have been compared with analogous data obtained in dimethylsulfoxide–water mixtures. The effect of carbonyl atom replacement in acetone molecule by sulphur atom (DMSO molecule) on the thermodynamic functions of complex formation has been analysed.     

Quantitative study of the quasiequilibrium in the system (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)-molybdenum(V)-piperidine in toluene medium

The quasiequilibrium interaction of (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)molybdenum(V) and piperidine in the toluene medium has been studied by means of chemical kinetics and spectrophotometric titration. It has been revealed that the molecular complex formation proceeds as slow irreversible salt formation reaction. It is preceded by the stages of equilibrium substitution of the hydroxo group OH-with piperidine, the outer sphere cationic complex formation [K ₁ (2.03±0.28)×10³ M^?1]; and by the coordination of the second piperidine molecule to the cationic complex (K ₂ 1.76±0.39 M^?1). The complex formation has been completely kinetically described: the rate equations and rate constants have been derived, and the rate limiting stage has been identified. In addition, the physicochemical data on the intermediates and products are presented. The prospects of application of the mixed porphyrin-containing complex as piperidine receptor, alkaloids and pharmaceuticals building block, have been justified.     

Solvent extraction of some divalent metal cations into nitrobenzene by using a synergistic mixture of strontium dicarbollylcobaltate and hexaethyl calix[6]arene hexaacetate

Extraction of microamounts of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of polypropylene glycol PPG 425 (L) has been investigated. The equilibrium data have been explained assuming that the complex species HL⁺ and CsL⁺ (L = PPG 425) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species in nitrobenzene saturated with water have been determined.     

Solvent extraction of cesium into nitrobenzene by using a synergistic mixture of hydrogen dicarbollylcobaltate and polypropylene glycol PPG 425

Extraction of microamounts of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of polypropylene glycol PPG 425 (L) has been investigated. The equilibrium data have been explained assuming that the complex species HL⁺ and CsL⁺ (L = PPG 425) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species in nitrobenzene saturated with water have been determined.     

The synthesis,crystal structures and SOD activities of a new ligand (Lse) and Co(Lse)2(SCN)2 complex [Lse = selenium ether bis‐(N‐1‐methyl‐ benzotriazole)]

A new ligand containing selenium, Se (CH₂‐N‐Btrzole)₂ (L^se) (Btrzole = benzotriazole) and its cobalt(II) complex, Co(L^se)₂(SCN)₂, have been synthesized and the molecular structures of the title compounds have been determined by X‐ray techniques. The L^se is a meso‐configuration with a symmetric plane through the Se center, the intermolecular weak interactions of Se? Se, Se? N and π? π stacking between benzotriazole rings to extend the molecular structure to two‐dimensional network configuration. In the Co(II) complex, the metal center is in a six‐coordinated octahedral environment. Two Co(II) atoms are linked by two ligands to form a 20‐membered macrocycle; the adjacent macrocycles are linked by coordinated bond of Co? N_bentrozole to extend an infinite double strained chain. The SOD activity of the ligand and Co(II) complex have been studied by using the pyrogallol autoxidation method; thermal properties and luminescent properties of Co(II) complex have been tested, and the details of those properties have been discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Complex Formation of Crown Ethers and Cations in Water–Organic Solvent Mixtures: Part XI. Effects of the Preferential Solvation of Benzo-15-Crown-5 and Acid-Base Properties of the Mixtures on the Thermodynamic Functions for Complex Formation of Benzo-15-Crown-5 with Na+ in Propan-1-ol–Water Mixtures at 298.15 K

The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na⁺) in the mixtures of propan-1-ol (PrOH) with water at 298.15 K have been calculated from experimental measurements. The equilibrium constants of B15C5/Na⁺ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by a calorimetric method. The complexes are enthalpy stabilized but entropy destabilized in the PrOH–H₂O mixtures. The effects of preferential solvation of B15C5 by molecules of the organic solvent, solvation of the sodium cation, as well as the acid-base properties of propan-1-ol–water mixtures on the complex formation processes are discussed.     

Synthesis,structure, and properties of a new multiredox-active Sn(IV) complex based on 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzoquinone and ferrocenylaldimine phenol

A new mixed-ligand tin(IV) complex 2 derived from 3,6-di-tert-butyl-o-benzoquinone and ferrocenylaldimine phenol 1 has been prepared and characterized by different physicochemical methods (IR, ¹HNMR, and ¹¹⁹Sn NMR spectroscopies). Electrochemical transformations of complex 2 have been studied by cyclic voltammetry. Catecholate and ferrocenyl groups have been found to take part in the redox transformations. Chemical oxidation of complex 2 with silver triflate in a dichloromethane solution has been studied. Formation of monocationic complex 2 ⁺ has been detected by EPR spectroscopy. The catecholate ligand has been found to be the primary redox center subjected to oxidation.     

Dual Catalysis with an IrIII–AuI Heterodimetallic Complex: Reduction of Nitroarenes by Transfer Hydrogenation using Primary Alcohols

A triazolyl‐di‐ylidene ligand has been used for the preparation of a homodimetallic complex of gold, and a heterodimetallic compound of gold and iridium. Both complexes have been fully characterized and their molecular structures have been determined by means of X‐ray diffraction. The catalytic properties of these two complexes have been evaluated in the reduction of nitroarenes by transfer hydrogenation using primary alcohols. The two complexes afford different reaction products; whereas the Au^I–Au^I catalyst yields a hydroxylamine, the Ir^III–Au^I complex facilitates the formation of an imine.     

Transition metal complexes with thiosemicarbazide-based ligands. Part LVI: Nickel(II) complex with 1,3-diphenylpyrazole-4-carboxaldehyde thiosemicarbazone and unusually deformed coordination geometry

Synthesis of a new nickel(II) complex, [Ni(Ph₂PzTSC-H)₂] with 1,3-diphenylpyrazole-4-carboxaldehyde thiosemicarbazone (Ph₂PzTSC), is described. The compounds have been characterized by elemental and thermal analysis, molar conductivity and spectral (UV–Vis, IR, ¹H NMR, and ¹³C NMR) measurements. In the case of complex the magnetic measurement has been also performed. Crystal and molecular structures of both the free ligand and the complex have been determined by single crystal X-ray analysis. It was found that the ligand coordinates in a bidentate NS fashion, in its deprotonated thioenolato form. The cis-square-planar geometry of the complex is significantly distorted tetrahedrally. The Cambridge Structural Database (CSD) study has been performed to obtain geometrical and structural informations on similar nickel(II) complexes in order to compare structural data.     

Kinetik und Mechanismus der Substitionsreaktionen von Komplexverbindungen. XXVI. Solvatation des [Cr(NCS)4(p-Anisidin)2]-Ions in Äthanol–Wasser-Mischungen

13 new complex salts of the [Cr(NCS)₄(p-anisidine)₂]^? have been synthesized and the solvation kinetics of this anion has been studied in ethanol-water mixtures. The first two NCS^? ions are exchanged for water molecules. In acid solutions the rate of this reaction is not influenced by the solvent composition. In parallel with this reaction, p-anisidine molecules are substituted, too, by ethanol molecules. (Acceleration by hydrogen ions.) In the resulting complex ion the first two NCS^? ions are substituted, too, by water molecules. The rate constants of this reaction are rather close to those of the reaction which leads to the exchange of the first two NCS^? ions in the initial complex. The third and fourth NCS^? ions are substituted only in neutral solutions by water molecules. Kinetic parameters have been derived for the substitution of the first two NCS^? ions and for the substitution of the p-anisidine molecules.     

Ligational,thermal, corrosion inhibition and antimicrobial properties of salicylidinebenzenesulphonylhydrazone

Summary Complexes of Cu^II, Co^II, Ni^II, Cd^II, Zn^II and Hg^II with salicylidinebenzenesulphonylhydrazone (HSBS) have been prepared and characterized by elemental analyses, molar conductivities, magnetic moments, spectral (visible, i.r., n.m.r.) and thermal (d.t.a., t.g., d.t.g.) measurements. The magnetic and spectral studies confirm that the Ni^II complex is square, whereas the Co^II complex is tetrahedral. The molar conductivities for the complexes lie in the non-electrolyte range. The corrosion inhibition of aluminium using HSBS was studied by chemical and electrochemical methods. Also, the antimicrobial activities of HSBS and its complexes have been investigated.     

Die Komplexbildung der neutralen Amidgruppe mit Cu2+ in wässeriger Lösung

The interaction between Cu²⁺ and the terdentate ligands N-picolinoyl-ethylenediamine, glycine-2-pyridylmethylamide, N^α-(2-pyridylmethyl)-glycinamide and N^α-(2-pyridylmethyl)-glycine-ethylamide, respectively, has been studied by spectrophotometry and potentiometry. At high pH values the ionised amide group undergoes complex formation and the resulting chelates have similar structures and stabilities. In slightly acidic solution however, each ligand gives rise to a different species. These facts are explained by assuming that the neutral amide group coordinates through its carbonyl oxygen atom. The stability constant and the absorption spectrum of each complex have been calculated by computer programmes.     

Cobalt(II), nickel(II), and copper(II) complexes with Schiff bases, derivatives of 1-amino-8-hydroxynaphthalene-2,4-disulfonic acid

Five new cobalt(II), nickel(II), and copper(II) complexes with Schiff bases have been synthesized. The Schiff bases have been prepared by the condensation of monopotassium 1-amino-8-hydroxynaphthalene-2,4-disulfonate with benzoin (L¹) or 2-hydroxy-1-naphthaldehyde (L²). The compounds have been identified and studied by elemental analysis, X-ray diffraction, thermogravimetry, measurements of magnetic susceptibility and electrical conductivity, and IR, ESR, and diffuse reflectance spectroscopy. The dimeric (with oxo bridges) structure of the Co(II) complex with L¹ has been additionally confirmed by the EXAFS method.     

Radium isotopes in suspended matter in an estuarine system in the southwest of Spain

The presence of²²⁶Ra and²²⁴Ra in suspended matter from an estuarine system which surrounds a phosphate fertilizer complex has been investigated. The results have confirmed an important radioactive impact from the industrial complex, since up to 2.5 Bq²²⁶Ra/g suspended matter (dry) has been measured. The influence of tides and seasonal conditions, through changes in salinity, has been found to be relevant. The distribution coefficients for²²⁶Ra between the suspended matter and the river water have been calculated. The values are in agreement by order of magnitude with those found in the literature, but they clearly depend on tidal state and seasonal conditions.     

Polymerized mixed aggregates containing gadolinium complex and CCK8 peptide

Two novel amphiphilic unimers containing an aliphatic hydrophobic chain (PDA) with two C≡C triple bonds and hydrophilic heads presenting the chelating agent DTPAGlu and the CCK8 bioactive peptide, respectively, have been prepared by solid phase synthesis. Aggregates obtained by mixing together PDA-DTPAGlu, or its Gd(III) complex, and PDA-L2-CCK8 in 70/30 molar ratio before and after a polymerization process carried out by UV irradiation have been structurally characterized by means of small angle neutron scattering. The relaxivity properties of aggregates containing Gadolinium complexes have also been investigated. Elongated mixed micelles have been observed, in which the relaxivity value r _1p for each Gadolinium complex, measured at 20 MHz and 298 K, is around 12 mM^–1 s^–1.     

Synthesis, characterisation and theoretical studies on some piano-stool ruthenium and rhodium complexes containing substituted phenyl imidazole ligands

Reactions of the chloro-bridged arene ruthenium complexes [{(η⁶-arene)RuCl(μ-Cl}₂] (η⁶-arene = benzene, p-cymene) and structurally analogous rhodium complex [{(η⁵-C₅Me₅)RhCl(μ-Cl}₂] with imidazole based ligands viz., 1-(4-nitro-phenyl)-imidazole (NOPI), 1-(4-formylphenyl)-imidazole (FPI) and 1-(4-hydroxyphenyl)-imidazole (HPI) have been investigated. The resulting complexes have been characterised by elemental analyses, IR, ¹H and ¹³C NMR, electronic absorption and emission spectral studies. Crystal structure of the representative complex [(η⁵-C₅Me₅)RhCl₂(NOPI)] has been determined crystallographically. Geometrical optimisation on the complexes have been performed using exchange correlation functional B3LYP. Optimised bond lengths and angles of the complexes have been found to be in good agreement with our earlier reports and single crystal X-ray data of the complex [(η⁵-C₅Me₅)RhCl₂(NOPI)].     

Determination and comparison of stability constants of tungsten(VI) and molybdenum(VI) with nitrilotriacetic acid and glutamic acid at different ionic strengths

The formation constants of species formed in the systems H⁺?+?W(VI)?+?nitrilotriacetic acid (NTA) and H⁺?+?NTA have been determined in aqueous solution for pH?=?4–9 at 25°C and different ionic strengths ranging from 0.1 to 1.0?mol?dm^?3 NaClO₄, using potentiometric and spectrophotometric techniques. It was shown that tungsten(VI) forms a mononuclear 1?:?1 complex with NTA of the type WO₃L^3? at pH?=?7.5. The composition of the complex was determined by the continuous variations method. The complexation of molybdenum(VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum(VI) forms a mononuclear 1?:?1 complex with glutamic acid of the type MoO₃L^2? at pH?=?6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25°C and at ionic strengths ranging from 0.1 to 1.0?mol?dm^?3 sodium perchlorate. In both complex formation reactions the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported.     

Spectrophotometric determination of molybdenum with Alizarin Red S in the presence of poly(sulfonylpiperidinylmethylene hydroxide)

The present work describes a selective and rapid method for the determination of molybdenum with Alizarin Red S (ARS) in the presence of a water soluble polymer, poly(sulfonylpiperidinylmethylene hydroxide) (PSPMH). The ARS modified by PSPMH reacts with molybdenum(VI) in the solutions of pH 3.4-4.0 to produce a red complex. The composition of the complex is 1:4:1 mol ratio of Mo(VI): ARS:PSPMH. The complex obeys Beer's law from 0.05 to 5.50 μg ml⁻¹ with an optimum range. The molar absorptivity is 2.1×10⁴ l mol⁻¹ cm⁻¹ at 500 nm. The interference effects of the foreign cations have been examined and it has been determined that only Cu(II), Al(III) and Fe(III) have to be masked by EDTA and tungsten can be tolerated till 4-fold of molybdenum in case of masking by citrate. The method has been applied to the determination of geological samples without solvent extraction or separation steps.     

Extraction of microamounts of calcium in the two-phase water-HCl-18-crown-6-nitrobenzene-hydrogen dicarbollylcobaltate system

Summary Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of 18-crown-6 (18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, CaL²⁺and CaL are extracted into the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water have been determined.     

Crystal structure and biological activities of water-soluble nickel(II) and copper(II) complexes of a Schiff-base derived from paeonol

Water-soluble Ni(II) and Cu(II) complexes of a flexible Schiff-base ligand have been synthesized, and the Ni(II) complex was characterized by X-ray crystallography. The interactions of the two complexes with calf thymus DNA were investigated by spectroscopic and viscosity measurements in water. The results suggest that the two complexes bind to DNA within the groove. Antioxidant experiments against OH^• and O₂^−• show that these two complexes have excellent ability to scavenge O₂^−•, and the Cu(II) complex exhibits better activity than the Ni(II) complex.