Dimerization and Coordination Properties of Zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine in Relation to DABCO in <Emphasis Type="Italic">o</Emphasis>-Xylene and Chloroform

For the first time the interactions between zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine (Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc) and 1,4-diazabicyclo[2.2.2]octane (DABCO) in o-xylene and chloroform have been studied by calorimetric titration and NMR and electron absorption spectroscopic methods. It has been found that in o-xylene at concentrations of Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc higher than 6×10⁻⁴ mol⋅L⁻¹ π–π dimers species are formed (λ _max= 685 nm). Additions of DABCO to the solution up to mole ratio 1 : 8 (Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc : DABCO) lead to a shift of the aggregation equilibrium towards monomer species due to formation of monoligand axial complexes. Further increasing the DABCO concentration results in formation of Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc—DABCO—Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc sandwich dimers (λ _max= 675 nm).     

Comparative absorption spectroscopy involving 4f-4f transitions to explore the kinetics of simultaneous coordination of uracil with Nd(III) and Zn(II) and its associated thermodynamics

The interaction of uracil with Nd(III) has been explored in presence and absence of Zn(II) using the comparative absorption spectroscopy involving the 4f-4f transitions in different solvents. The complexation of uracil with Nd(III) is indicated by the change in intensity of 4f-4f bands expressing in terms of significant change in oscillator strength and Judd-Ofelt parameters. Intensification of this bands became more prominent in presence of Zn(II) suggesting the stimulative effect of Zn(II) towards the complexation of Nd(III) with uracil. Other spectral parameters namely Slator-Condon (F(k)'s), nephelauxetic effect (β), bonding (b(1/2)) and percent covalency (δ) parameters are computed to correlate their simultaneous binding of metal ions with uracil. The sensitivities of the observed 4f-4f transitions towards the minor coordination changes around Nd(III) has been used to monitor the simultaneous coordination of uracil with Nd(III) and Zn(II). The variation of intensities (oscillator strengths and Judd-Ofelt parameters) of 4f-4f bands during the complexation has helped in following the heterobimetallic complexation of uracil. Rate of complexation with respect to hypersensitive transition was evaluated. Energy of activation and thermodynamic parameters for the complexation reaction were also determined.     

The outer-sphere association of p-sulfonatothiacalix[4]arene with some Co(III) complexes: the effect on their redox activity in aqueous solutions

The effect of the ion-pairing of Co(III) complexes with p-sulfonatothiacalix[4]arene (STCA) on Fe(II)–Co(III) electron transfer rate was evaluated from the analysis and comparison of kinetic data in double Co(III)–Fe(II) and triple Co(III)–Fe(II)—STCA systems at various concentration conditions. Complexes [Co(en)₃]³⁺(1), [Co(en)₂ox]⁺(2), [Co(dipy)₃]³⁺ (3), [Co(His)₂]⁺(4) and [Fe(CN)₆]⁴⁻ were chosen as Co(III) and Fe(II) compounds. The effect of STCA was found to correlate with the association mode. The outer-sphere association with STCA was found to exhibit the insignificant effect on Fe(II)–Co(III) electron transfer k _et constants for complexes 3 and 4 with bulky and rigid chelate rings, while more sufficient inclusion of flexible ethylendiaminate rings of 1 and 2 into the cavity of STCA results in the unusual increase of k _et.     

A Polyaza Macrocycle Ligand Bearing Anthracenyl Fluorophores for Selective Signaling of Zn(II) in Aqueous Solution

Based on a metal-template synthetic strategy, a new polyaza macrocycle bearing two anthracenyl fluorophores ligand, N,N′-bis[(anthracen-10-yl)methylene]-5,6,8,9,14,15,17,18-octahydrodibenzo[f,m][1,3,5,8,10,12]hexaazacyclotetradecine-7,16-diamine (L), was prepared and fully characterized. In the presence of Zn(II), L displayed remarkable chelation-enhanced fluorescence and can selectively respond to the presence of Zn(II) ion compared with other cations in HEPES-buffered aqueous methanol solutions. Results obtained from UV–Vis and fluorescence titrations indicated that L chelates to Zn(II) by forming a complex with a 1:1 molar ratio.     

Stability of isomerous chelates in M(II)-thiocarbamoylmethanamide-ethandial systems according to the DFT B3LYP method (M = Mn, Fe, Co, Ni, Cu, Zn)

Calculations of the optimal geometry and standard thermodynamic parameters of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) isomerous macrotricyclic complexes with MN₂O₂, MN₂S₂, and MN₄ chelate bonds, which can in principle appear as a result of template processes between gelatine-immobilized hexacyanoferrates (II) of corresponding M(II) metal ions, thiocarbamoylmethaneamide (thiooxamide) H₂N-C(=S)-C(=O)-NH₂, and ethanedial HC(=O)-CH(=O), were performed according to the B3LYP hybrid density functional method using a 6-31G(d) basis set with the Gaussian 98 program. It was found that of all of the considered M(II), the most stable are complexes with MN₄ chelate bonds, where the values of a standard enthalpy Δ_f H ₂₉₈^o and a standard Gibbs energy, Δ_f G ^o for all complexes studied are positive.     

Ultrasonic studies of polysaccharide (pectin) in aqueous media at 298.15 K

The ultrasonic velocity, density and viscosity of pectin in aqueous medium were measured at 298.15 K. The acoustical parameters such as adiabatic compressibility (β), free length (L _f), free volume (V _f), internal pressure (π_i), acoustical impedance (Z), and relative association (R _A), Rao’s constant (R) and Wada’s constant (W) are calculated. The results are interpreted in terms of molecular interaction between the components of the mixtures. Further, some more acoustical parameters such as relaxation time (τ), absorption coefficient (α/f ²) and relaxation strength (r) are calculated with various percentage of pectin has been studied which reveals interaction between the solvent and the polymer (pectin) at various concentration of the polymer. The observed values suggested the solute-solvent interaction is favored.     

Thermal stability of porcine pepsin influenced by Al(III) ion: DSC study

Differential scanning calorimetry (DCS) has been used to determine thermodynamic profile of pepsin and the in vitro effect of Al(III) ions. Thermograms of pepsin unfolding in the presence and absence of aluminum were used to determine the binding constant, K _L, in the pepsin-aluminium model system. The thermodynamic parameters were derived from DSC profiles at different ligand concentrations (1, 5 and 10 mM). The temperatures of thermal transitions (T _m), calorimetric (ΔH ^cal) and van’t Hoff enthalpy (ΔH ^VH), Gibbs free energy, Δ(ΔG), of Al(III) binding to pepsin, as well as an average number of ligands bound to the native protein, were obtained from DSC profiles too. Temperature-dependent changes in the protein structure were also monitored by native PAGE electrophoresis. Increasing the temperature causes the decrease in electrophoretic mobility. Increase in concentration of Al(III) decelerate the migration of pepsin samples on concentration dependent manner. Analysis showed that ligand binding increases thermal stability of protein.     

Calculation of electric dipole intensity parameters of 4f-4f transitions of Pr(III) and glutathione reduced (GSH) complex in presence and absence of Zn(II)

Comparative absorption and spectral analysis of 4f-4f transitions of Pr(III) and glutathione reduced (GSH) complex in presence and absence of Zn(II) is carried out in different aquated organic solvents of CH3OH, CH3CN, DMF and dioxane and their equimolar mixtures at different pH (3.0, 4.0, 5.0 and 6.0). The values of experimentally calculated oscillator strengths (P) and computed values of Judd-Ofelt electric dipole intensity parameters, Tlambda (lambda=2, 4, 6) are discussed for different 4f-4f transitions in different experimental conditions. The changes in the values of oscillator strengths (P) and Tlambda parameters suggest the specific correlation between relative intensities, ligand structures and nature of interaction of Pr(III) with GSH in the presence and absence of Zn(II).     

Complexation and Electronic Spectra of Neodymium(III)–Amino Acid–1,10-Phenanthroline Systems in Aqueous Solution

Complexation of neodymium(III)-glutamate(glu)-phenanthroline(phen), neodymium(III)-aspartate(asp)-phenanthroline(phen) ternary systems and the corresponding binary systems in aqueous solution are discussed at various values of pH. Based on change regularity of hypersensitive transition intensities, the neodymium(III)-aspartate-phenanthroline ternary complex has a general formula of Nd(asp)₃phen, but the composition of the complex of Nd(III) with glutamate and phenanthroline is complicated and has not been determined. The electronic spectra of these complexes were studied, Slater-Condon parametersF _k ^s and the Lande parameter ξ_4f were obtained. The rms deviation between calculated and observed energy levels is less than 43 cm⁻¹. Bonding in these complexes are also investigated and bonding parameters calculated. The results show that Nd(III) and amino acids form complexes by ionic linkage with carboxylic oxygens, but with some weak covalency. Besides, the degrees of covalency in ternary complexes are larger than those in binary complexes.     

Regularities of complexation in the series of sorbents on the polystyrene matrix and their complexes with chromium(III) and manganese(II)

The physicochemical properties of polymeric complexing sorbents with the o,o′-dihydroxy-(1-azo-1′)-functional complexing group were studied. Optimal sorption parameters for chromium(III) and manganese(II) (medium acidity, temperature, time), the sorption capacity of the sorbents, and the stability constants (pK _a′)of the complexes were determined. Correlation relations were established between the dissociation constants (pK _a′) of the sorbent functional group and pH₅₀ of the complexation of the considered elements; between and the stability of the formed complexes (logβ); and between pK _a′ and the deprotonation energy (E _depr) of the sorbent hydroxy group located in the para-position to the introduced substituent. The established correlation relations are useful for targeted prediction of the physicochemical parameters of the sorbents, their complexes, and the sorption of manganese(II) and chromium(III) aimed at recovery and pre-concentration of these ions from objects with various chemical composition.     

Effect of Temperature and Solvent on the Ultrasonic Velocity and Allied Acoustical Parameters of the Epoxy Oleate of 9,9′-Bis(4-hydroxyphenyl) Anthrone-10 Solutions

Density (ρ), viscosity (η) and ultrasonic velocity (U) (2 MHz) of the pure solvents (chloroform, THF and 1,4-dioxane) and solutions of the epoxy oleate of 9,9′-bis(4-hydroxyphenyl) anthrone-10 (EBANO) have been investigated at 303, 308 and 313 K. Acoustical parameters such as specific acoustical impedance (Z), adiabatic compressibility (κ _a ), intermolecular free path length (L _f ), classical absorption coefficient (α/f ²)_cl and viscous relaxation time (τ) have been determined from the ρ, η and U data and are correlated with concentration. A fairly good to excellent correlation between a given parameter and concentration is observed at all temperatures and solvent systems studied. Linear or nonlinear increases or decreases of acoustical parameters with concentration and temperature indicated the existence of strong molecular interactions.     

Zinc(II) complex of the edta bis(tyrosine) chelating agent

The synthesis and results of X-ray structural analysis for a novel zinc(II) compound, Zn(O₁₂N₄C₂₈H₃₂)·₆H₂O, are reported. The compound is triclinic, P1, with unit cell parameters a = 11.0906(3) Å, b = 13.1404(3) Å, c = 14.0725(3) Å; β = 89.910(1)°. In contrast to the analogous Cu(II) complex, the unit cell contains two independent molecules of the Zn(II) complex and twelve independent molecules of water. The text was submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 48, No. 4, pp. 760–763, July–August, 2007.     

Thermodynamic characteristics of triphenylantimony bis(acetophenoneoximate)

The temperature dependence of heat capacity C _p ^° = f(T) of triphenylantimony bis(acetophenoneoximate) Ph₃Sb(ONCPhMe)₂ was measured for the first time in an adiabatic vacuum calorimeter in the range of 6.5–370 K and a differential scanning calorimeter in the range of 350–463 K. The temperature, enthalpy, and entropy of fusion were determined. Treatment of low-temperature (20 K ≤ T ≤ 50 K) heat capacity was performed on the basis of Debye’s theory of the heat capacity of solids and its multifractal model and, as a consequence, a conclusion was drawn on the type of structure topology. Standard thermodynamic functions C _p ^°(T), H°(T) — H°(0), S°(T), and G°(T) — H°(0) were calculated according to the experimental data obtained for the compound mentioned in the crystalline and liquid states for the range of T → 0–460 K. The standard entropy of the formation of crystalline Ph₃Sb(ONCPhMe)₂ was determined at T = 298.15 K.     

Fluorescent ion-imprinted polymers for selective Cu(II) optosensing

This paper describes the synthesis and characterization of a fluorescent ion-imprinted polymer (IIP) for selective determination of copper ions in aqueous samples. The IIP has been prepared using a novel functional monomer, 4-[(E)-2-(4′-methyl-2,2′-bipyridin-4-yl)vinyl]phenyl methacrylate (abbreviated as BSOMe) that has been spectroscopically characterized in methanolic solution, in the absence and in the presence of several metal ions, including Cd(II), Cu(II), Hg(II), Ni(II), Pb(II), and Zn(II). The stability constant (2.04 × 10⁸ mol⁻² l²) and stoichiometry (L₂M) of the BSOMe complex with Cu(II) were extracted thereof. Cu(II)-IIPs were prepared by radical polymerization using stoichiometric amounts of the fluorescent monomer and the template metal ion. The resulting cross-linked network did not show any leaching of the immobilized ligand allowing determination of Cu(II) in aqueous samples by fluorescence quenching measurements. Several parameters affecting optosensor performance have been optimized, including sample pH, ionic strength, or polymer regeneration for online analysis of water samples. The synthesized Cu(II)-IIP exhibits a detection limit of 0.04 μmol l⁻¹ for the determination of Cu(II) in water samples with a reproducibility of 3%, exhibiting an excellent selectivity towards the template ion over other metal ions with the same charge and close ionic radius. The IIP-based optosensor has been repeatedly used and regenerated for more than 50 cycles without a significant decrease in the luminescent properties and binding affinity of the sensing phase.     

Coordination chemistry of perfluoroalkylated phosphorus(III) ligands

Palladium(II), platinum(II), rhodium(I), rhodium(III) and iridium(III) complexes of the tridecafluorohexyl-derivatised diphenylethylphosphinite (PPh₂OC₂H₄R_f), phenyldiethylphosphonite {PPh(OC₂H₄R_f)₂}, triethylphosphite {P(OC₂H₄R_f)₃}, triphenylphosphinite (PPh₂OC₆H₄-4-R_f), triphenylphosphonite {PPh(OC₆H₄-4-R_f)₂}, ethyldiphenylphosphine (PPh₂C₂H₄R_f), diethylphenylphosphine {PPh(C₂H₄R_f)₂} and triethylphosphine {P(C₂H₄R_f)₃} ligands are synthesized by conventional ligand displacement and/or halide-bridge cleaved reactions, and their spectroscopic parameters are compared with those for the related ligands lacking the tridecafluorohexyl ponytails.     

The relative stability of macrotricyclic metal complexes in M(II)-thiocarbohydrazide-acetone (M = Mn, Fe, Co, Ni, Cu, Zn) ternary systems according to the data of quantum-chemical calculations

The B3LYP hybrid method of density functional theory with the 6–31G(d) basis set was used to calculate the optimum geometry and standard thermodynamic parameters of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) macrotricyclic complexes with MN₂S₂ and MN₄ chelate nodes. The calculations were performed using the Gaussian 98 package. Such complexes could in principle appear because of temperature processes between gelatin-immobilized hexacyanoferrates(II) of the corresponding M(II) metal ions, thiocarbohydrazide, and acetone. For all the M(II) metals considered, complexes with MN₂S₂ chelate nodes were stablest. The standard Gibbs energies Δ_f G ₂₉₈^° values were positive for all the complexes specified.     

Studies on the Synthesis and Potentiometric Properties of Three Novel Tripodal Ligands and their Complexes

Three novel tripodal ligands, N,N′,N′′-tri-(3′-phenylpropionic acid-2′-yl-)-1,3,5-triaminomethylbenzene (Ll), N,N′,N′′-tri-(4′-methylvaleric acid-2′-y1-)-1,3,5-triaminomethylbenzene (L2) and N,N′,N′′-tri-(3′methylvaleric acid-2′-yl-)-1,3,5-triaminomethylbenzene (L3), have been synthesized and fully characterized. The stabilizing ability of complexes of the three ligands with transition metal ions Cu(II), Ni(II), Zn(II) and Co(II) and rare earth metal ions La(III), Nd(III), Sm(III), Eu(III) and Gd(III) has been investigated by the pontentiometric method in water and in aqueous KNO₃ (0.1 mol dm⁻³) at 25.0±0.1 °C, respectively. The results show that there is a great deal of difference between two series of complexes’ stabilities. An explanation of the difference has been given.     

Synthesis and characterization of Pr(III), Nd(III) and Er(III) complexes with 2,6-pyridinedimethanol

The reactions of Ln(NO₃)₃?6H₂O (Ln=Pr, Nd or Er) with the potentially tridentate O,N,O chelating ligand 2,6-pyridinedimethanol (H₂pydm) in a 1:2 M ratio were investigated, and complexes with the formula [Ln(H₂pydm)₂(NO₃)₂](NO₃) (Ln=Pr or Nd) (1 and 2) and [Er(H₂pydm)₃](NO₃)₃ (3) were isolated. The compounds contain 10-coordinate Pr(III) and Nd(III) ions that crystallize in the triclinic space group P-1 while the 9-coordinate Er(III) complex crystallizes in the monoclinic system (P2₁/n). A new lanthanide complex, [Pr(H₂pydm)₃](Cl)₃?DMF (4), has been synthesized by reaction of PrCl₃?6H₂O and H₂pydm. The nine-coordinate Pr(III) is bound to three H₂pydm ligands. X-ray crystal structures of 1–4 reveal that the ligand coordinates tridentate via the pyridyl nitrogen and the two hydroxyl oxygens. The electronic absorption spectra of 1–4 show 4f–4f transitions.     

Tetrad effect in mixed-ligand lanthanide chelates. Part II: Lanthanide. CDTA/DTPA. orcinol/resorcinol/phloroglucinol ternary systems

The variation profiles of certain properties of the lanthanide [Ln(III)] series show discontinuities at or around Gd(III) (4f⁷ stage), Nd (IH)-Pm(III) (4f³−4f⁴ stage) and Ho (III)-Er (III) (4f¹⁰−4f¹¹ stage) due to the presence of a tetrad effect. In the present work the occurrence of the tetradic phenomenon has been studied for the formation constants, log K _MAL ^MA of the mixed-ligand Ln (III) chelates of the type [Ln(III).A.L], where Ln(III) = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb (III) or Dy(III); A = CDTA or DTPA; L = orcinol, resorcinol or phloroglucinol. The presence of the tetrad effect in log K _MAL ^MA values has been tested with the help of the straight line approximation method, differential plot method and inclined-W hypothesis. The magnitude of the effect has been found to lie in the sequence f⁷ > f³ −f⁴.     

Coordination Reaction of Alanine with Neodymium(III) and Erbium(III) Nitrate. Thermochemical study

The solid-state coordination reaction: Nd(NO₃)₃·6H₂O(s)+4Ala(s) → Nd(Ala)₄(NO₃)₃·H₂O(s)+5H₂O(_l) and Er(NO₃)₃·6H₂O(s)+4Ala(s) → Er(Ala)₄(NO₃)₃·H₂O(s)+5H₂O(l) have been studied by classical solution calorimetry. The molar dissolution enthalpies of the reactants and the products in 2 mol L^–1 HCl solvent of these two solid-solid coordination reactions have been measured using a calorimeter. From the results and other auxiliary quantities, the standard molar formation enthalpies of [Nd(Ala)₄(NO₃)₃·H₂O, s, 298.2 K] and[Er(Ala)₄(NO₃)₃·H₂O, s,298.2 K] at 298.2 K have been determined to be Δ_f H _m ⁰ [Nd(Ala)₄(NO₃)₃·H₂O,s, 298.2 K]=–3867.2 kJ mol^–1, and Δ_f H _m ⁰ [Er(Ala)₄(NO₃)₃·H₂O, s, 298.2 K]=–3821.5 kJ mol^–1. This revised version was published online in August 2006 with corrections to the Cover Date.