Ternary Complexes in Solution: Mixed Ligand Pb(II) Complexes with 2,2′-Bipyridyl or 1,10-Phenanthroline and Some Bivalent Mercapto Acid Amides

Abstract

The stability constants of ternary Pb(II) complexes containing 2,2′-bipyridyl (Bipy) or 1,10-phenanthroline (phen) as the first ligand and N-phenyl-2-mercapto acid amide, N-(p-chloro)phenyl-2-mercapto acid amide, N-(p-tolyl)-2-mercapto acid amide, N-(p-anisyl)-2-mercapto acid amide, or N-phenyl-2-mercapto-propionamide as the second ligand were determined in 70% v/v dioxane-water medium at 30 ± 1°C and constant ionic strength (0.1 M NaClO₄) in a nitrogen atmosphere. The results give evidence that all these complexes have the same structure and therefore the binding sites of the ligands have to be the imino nitrogen and sulfur of the sulfhydryl group. The stability difference between the ternary and the binary complexes are in good agreement with this interpretation. It is of interest to note that these ternary complexes are significantly more stable than expected from statistical reasons, i.e., the difference; Δ log K_M = log K^MA _MAL - log K^M _ML is positive (except for PMP) (where A = Bipy or phen and L is the second ligand). In addition, the enhanced stability of the ternary complexes is suggested on the basis of the π-accepting qualities of the hetero aromatic N-base. The effect of the chelate ring size is discussed.     

Mixed Ligand Complex Formation Reactions and Equilibrium Studies of Cu(II) with Bidentate Heterocyclic Alcohol (N,O) and Some Bio-Relevant Ligands

The formation equilibria of copper(II) complexes and the ternary complexes Cu(HMI)L (HMI=4-Hydroxymethyl-imidazole, L=amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(HMI)L and Cu(HMI,H₋₁)(L) complexes. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters Δlog ₁₀ K and log ₁₀ X. The effect of the side chains of amino acid ligands (Δ_R) on complex formation was discussed. The concentration distributions of various species formed in solution were also evaluated as a function of pH. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants are investigated. The effects of dioxane as a solvent, on the protonation constant of HMI and the formation constants of Cu^II–HMI complexes, were discussed.     

Complexes of Cu(II) with 2,2′-dipyridyl and some malonic acids

The stability constants of ternary complexes containing copper(II), 2,2′-dipyridyl and a set of mono- and di-substituted malonic acids, were obtained by potentiometric titrations. The results are discussed in terms of substituent influences upon the chelation of the malonic dianions to the system Cu(dip). It is suggested that the electronic and geometric characteristics of the strongest ligand, govern the coordination of the second one.     

A Novel Cu(II) Complex with 2,2′-Bipyridyl and L-Methioninate──Synthesis, Characterization, Molecular Structure and Stability

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Mixed Ligand Complexes of 5-arylazo-8-hydroxyquinoline and α-amino Acids with Co(II), Ni(II) and Cu(II)

Ten mixed ligand complexes of the type [M(X-QA)(aa)] and [Ni(X-QA)₂(Haa)(H₂O)],where X-HQA=5-arylazo-8-hydroxyquinoline derivatives, M=Co(II) orCu(II) and Haa=glycine (gly), alanine (ala) or methionine (met), have been prepared. The complexes have been characterized by elemental analysis, IR and electron spectra and thermal analysis. A tetrahedral structure has been proposed for the cobalt(II) and copper(II) complexes with bidentate coordination of amino acids. The nickel(II) complexes have been assigned an octahedral structure with the amino acids acting as monodentate ligands. The thermal behaviour of the complexes has been studied before and after γ-irradiation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and Structural Studies of Some β-Diketone Phenylhydrazones and their Complexes with Co(II), Ni(II), and Cu(II)

Summary.  New β-diketone phenylhydrazones prepared by condensation of substituted 3-arylidene-2,4-pentanediones with phenylhydrazine, have been characterized by their elemental analyses, IR, ¹H NMR, and mass spectra. Some complexes of these Schiff bases with Co(II), Ni(II), and Cu(II) ions have been synthesized; in addition to the above methods, their structures were studied by magnetic susceptibility and thermogravimetry measurements. Received January 26, 2000. Accepted (revised) April 14, 2000     

A Novel Cu(Ⅱ） Complex with 2,2′-Bipyridyl and L-Methioninate -synthesis,Characterization,Molecular Structure and Stability

The ternary Cu(II) complex with 2,2′‐bipyridyl (bipy) and L‐methioninate (L‐Met) has been synthesized and characterized by elemental analysis, molar conductivity, UV‐Vis spectra, IR spectra and pH‐potentiometric titration methods. The structure of the complex [Cu(L‐Met) (bipy) (H₂O)]ClO₄ · 3/8H₂O was characterized by the X‐ray diffraction analysis. It crystallizes in the triclinic system, space group P1 with four molecules in a unit cell of dimensions, a = 0.7656(2) nm, b = 1.3142(3) nm, c = 2.0596(4) nm, α = 97.70(3)°, β = 97.96(3)°, γ = 94.33(3)°, V= 2.0244(8) nm³, R₁, = 0.0441 and wR₂ = 0.0678. The crystal contains four crystllographically independent [Cu(L‐Met) (bipy) (H₂O)]⁺ complexes (Cu1—Cu4), having a distorted square‐pyramidal geometry with the same coordinated atoms around each copper center. The base plane is occupied by two nitrogen atoms of one bipy, the amino nitrogen atom and one carboxylate oxygen atom from each independent L‐Met moiety, and one water oxygen at an axial position. Cu1 and Cu3 are essentially enantiomers of Cu2 and Cu4. The four molecules are packed with each other by intermolecular hydrogen‐bonding and aromatic‐ring stacking interactions.     

Thermodynamics of Formation of Molecular Complexes of Aromatic Nitro Derivatives with Lincomycin and β-Glycyrrhizic Acid

It was found that lincomycin and -glycyrrhizic acid form 1:2 molecular complexes with aromatic nitro derivatives. Quantum-chemical calculations of lincomycin and -glycyrrhizic acid were performed. These compounds form a cavity and, like podands, are capable of accommodating guest molecules. The formation constants and the thermodynamic characteristics of the complexes were calculated. A linear correlation was found between the formation constants of the molecular complexes of -glycyrrhizic acid and the Hammett constants of the substituents in the nitro derivatives. The complexes of lincomycin and -glycyrrhizic acid with aromatic nitro derivatives are formed by a common mechanism involving related bonds.     

Complexes of Te(IV), Te(II) and Se(II) with 2,2′-iminodiethanoldithiocarbamate

Novel complexes of 2,2′-iminodiethanoldithiocarbamate (DEADTC⁻) with Te(IV), Te(II) and Se(II) having the composition Te(DEADTC)₄, Te(DEADTC)₂I₂, Te(DEADTC)₃I, Te(DEADTC)₂ and Se(DEADTC)₂ were isolated and characterised by X-ray, magnetic, spectral (UV, IR) and conductance and molecular weight measurements. 2,2′-Iminodiethanoldithiocarbamate is shown to be weaker in its ligation behaviour than diethyldithiocarbamate.     

Physico‐Chemical Studies on Cu(II) Complexes of Acrylate Chelating Polymers

Abstract

Metal chelating polymers containing amide and carboxylic groups were prepared by gamma‐radiation polymerization of acrylic acid (AA) monomers in the presence of polyacrylamide (PAM). The resins obtained were loaded by copper ions and characterized by FT‐IR spectroscopy, electron spin resonance (ESR), thermogravimetric analysis (TGA), and differential scanning calorimetery (DSC). The IR spectra indicated a lower frequencies shift in the carbonyl bands due to copper ion chelation with carbonyl groups in the polymer resins. Also, the IR spectra reveal a splitting in the band at 3600–3200?cm^?1 that due to the coordination of the NH and OH groups with copper ions. The ESR spectrum was anisotropic with hyperfine structure having the following values 2.3808 and 2.07218 for g _∥ and g _⊥, respectively. These spectra for copper ions have square planar coordination with two nitrogen and two oxygen atoms. TGA and DSC studies show that radiation crosslinking and complexation with copper ion increase the thermal stability of PAM–AA resins. Meanwhile, resin complexes with copper ion showed a higher thermal stability than pure resin. The increase in thermal stability may be correlated with the metal ions coordination with NH and OH groups; this coordination prevents the splitting of ammonia and water molecules. Also, the metal ions providing a coordination crosslink between polymer chains could increase thermal stability.     

Synthesis,characterization, and interaction with DNA of Cu(II) and Zn(II) complexes with 2,2′-bipyridyl-6,6′-dicarboxylic acid

Two transition metal complexes, [Cu₂(bpdc)₂H₂O]·2H₂O (1) and Zn(bpdc)(H₂O)₂ (2) (H₂bpdc?=?2,2′-bipyridine-6,6′-dicarboxylic acid), were synthesized and characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Complex 1 is dinuclear with two five-coordinate cupric ions and 2 is mononuclear with one six-coordinate zinc. Interactions of 1 and 2 with DNA have been investigated using UV–Vis absorption spectra. The cleavage reaction on DNA has been monitored by agarose gel electrophoresis.     

Synthesis and Crystal Structure of Bis(2,2′-Bipyridine-N,N′)Dichloromanganese(II) Complex with Free 2,2′-Bipyridine

The title complex [Mn(bipy)₂Cl₂]·0.5bipy·2.5H₂O, where bipy = 2,2'-bipyridine, has been prepared and its crystal structure has been determined by X-ray diffraction methods. The complex crystallizes in the triclinic space group P-1, with a = 8.814(2), b = 11.335(2), c = 13.347(3) Å, α = 76.85(2), β = 89.55(2), γ = 86.52(2)°. Two chloride and two bipy ligands cis-coordinate to a Mn(II) atom with a distorted octahedral geometry. The crystal consists of Mn(II) complex, free bipy and crystalline water. The complex crystalline water link to each other by H-bonding to form supra-molecular chains, and free bipy molecules locate between parallel chains with a van der Waals contact distance of 3.58(1) Å. A π-π interaction is also observed between adjacent bipy rings. The chelating bipy and free bipy showed different IR absorptions.     

2,4′-Bipyridyl complexes with cobalt(II) and nickel(II)

Summary Complexes of empirical formulae [ML₂Cl₂(OH₂)₂], [CoL₂Br₂(OH₂)₂]L·4H₂O, [NiL₂Br₂(OH₂)₂]L₂·2H₂O, [ML₂(OH₂)₄]L₂(NO₃)₂ and [ML₄(OH₂)₂](ClO₄)₂·2H₂O (M = Co^II, Ni^II, L = 2,4-bipyridyl) were synthesized and characterized by elemental and spectral analyses. The thermal decomposition of the complexes was also investigated.Author to whom all correspondence should be directed.     

Speciation of the Vanadium(III) Complexes with 1,10-Phenanthroline, 2,2′-Bipyridine,and 8-Hydroxyquinoline

The complex species formed between vanadium(III) and 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy), and 8-hydroxyquinoline (8hq) were studied in aqueous solution by means of electromotive forces measurements, emf(H), at 25 °C with 3.0 mol⋅dm⁻³ KCl as the ionic medium. The potentiometric data were analyzed using the least-squares computational program LETAGROP, taking into account the hydrolytic vanadium(III) species formed in solution. Analysis of the vanadium(III)–phen system data shows the formation of [VHL]⁴⁺, [V(OH)L]²⁺, [V₂OL₂]⁴⁺ and [V₂OL₄]⁴⁺ complexes. In the vanadium(III)–bipy system the [VHL]⁴⁺, [V(OH)L]²⁺, [V₂OL₂]⁴⁺ and [V₂OL₄]⁴⁺ complexes were observed, and in the vanadium(III)–8hq system the complexes [V(OH)L]⁺, [V(OH)₂L], [VL₂]⁺ and [VL₃] were detected.     

Photochemical Behavior of Platinum(II) and Palladium(II) Complexes of 4,4′-Dimethyl-2,2′-Bipyridine

Several mixed-ligand complexes of formula [MX 2 (MBPY)] {where M is Pd(II) or Pt(II); X is Cl m , I m , N 3 m or NO 2 m and MBPY is 4,4'-dimethyl-2,2'-bipyridine} have been prepared. The UV-Vis spectra of these complexes were found to show a low-lying MLCT band and on irradiation at the MLCT band these complexes sensitize the oxidation of 2,2,6,6-tetramethyl-4-piperidinol (XH) in N , N -dimethylformamide (DMF) to 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinoloxy free radical (XO). This photo-oxidation reaction involves singlet molecular oxygen ( 1 O 2 ) as an intermediate and its presence was confirmed by quenching studies using bis(diethyldithiocarbamato)nickel(II) [Ni(DDTC) 2 ], a well-known 1 O 2 quencher. The ability of the complexes to photosensitize the above photo-oxidation reaction follows the order: [Pt ( N 3 ) 2 ( MBPY ) ] ( 2 ) ～ [Pt ( NO 2 ) 2 ( MBPY ) ] ( 3 ) > [PtCl 2 ( MBPY ) ] ( 4 ) > [PtI 2 ( MBPY ) ] ( 1 ) > [Pd ( NO 2 ) 2 ( MBPY ) ] ( 7 ) ～ [Pd ( N 3 ) 2 ( MBPY ) ] ( 6 ) > [PdCl 2 ( MBPY ) ] ( 8 ) > [PdI 2 ( MBPY ) ] ( 5 ), which reflects the nature of the metal ion and the nature of the ligands present in the complexes.     

Equilibrium Studies of Schiff Bases and Their Complexes with Ni(II), Cu(II) and Zn(II) derived from Salicylaldehyde and Some α-Amino Acids

The acid-base equilibria of Schiff bases derived from salicylaldehyde, glycine, alanine, serine, tyrosine, and phenylalanine, and their Ni(II), Cu(II) and Zn(II) complex formation equilibria were investigated by a potentiometric method in aqueous solution (t = 25^∘C, μ = 0.1 M, KCl). The data from the potentiometric titrations were evaluated by means of the BEST computer program. The order of the formation constant values of the Schiff bases was Sal-Ala > Sal-Gly > Sal-Ser > Sal-Phe > Sal-Tyr, which is the same order as the increasing log K₁ values of amino acids (and the log K₂ values of tyrosine) with the exception of an inversion between serine and phenylalanine. Also, it was seen that the stability constants, log β₁ and log β₂, of Schiff base–metal complexes vary for all the metal ions investigated, viz., Sal-Gly > Sal-Ala > Sal-Ser > Sal-Tyr > Sal-Phe with the exception of Sal-Gly in the copper complex. The effect of the nature of the amino acids on their formation, protonation and stability constants was also discussed.     

β-Cyclodextrin Inclusion Complexes of Aromatic Amines and Nitrocompounds and their Photoinduced Electron Transfer Reaction with the Tris(2,2'-bipyridine)ruthenium(II) Complex

The formation of -cyclodextrin (-CD) inclusioncomplexes of aromatic amines and nitrocompounds have been studied by absorptionand emission spectral methods. Among the different compounds studied, p-nitrobenzoic acid showed the smallest K_f value. 3,5-dinitrobenzoic acid showed the highest K_f value due to the formation of a hydrogenbond between the nitro group and the hydrogen in the hydroxyl groupof CD, and this is not possible with p-nitrobenzoic acid. The lower K_f values in the range 60–70 observed for ortho substituted compounds indicate the steric effect imposed by the ortho substitution of the compound. The para substituted compounds showed higher K_f values in the range 110–130 due to the hydrophobic effect and also due tothe absence of a steric effect. The lifetime of the Ru(II) complex is not affected by the presence of -CD. When the aromatic amines and nitrocompounds are used as quenchers for the excited state [Ru(bpy)₃]²⁺, the quenching rate constant (k_q) values are not significantly affected by the presence of -CD. This indicates that the electron donor or electronacceptor groups are not included into the cavity of -CD.     

2,4′-Bipyridyl complexes with silver(I) and copper(II)

Summary Ag^I and Cu^II complexes with 2,4-bipyridyl (2,4-bipy or L) with the general formulae AgL₂X (where X = NO _inf3 ^sup– or ClO₄ ^-), CuL₂X₂·2H₂O (X = Cl^- or Br^-), CuL₄SO₄·4H₂O, CuL₄(NO₃)₂·2H₂O and CuL₄(ClO₄)₂·H₂O have been isolated pure and characterized by analytical, spectral and magnetic measurements. The thermal decomposition of these complexes was studied under non-isothermal conditions in air.     

Syntheses and Crystal Structures of Three Palladium(II) Complexes with Isonitrosobenzoylacetoneimine Ligand

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