Studies on copper(II) complexes of some polyaza macrocycles derived from 1,2-diaminoethane

Syntheses of copper(II) complexes of 20-membered and 15-membered aza macrocycles 1,3,6,8,11,13,16,18-octaaza-2,7,12,17-tetrachlorocycloeicosane (OTCE, [20]-N₈) and 1,3,6,8, 11,13-hexaazacyclopentadecane (HCPD, [15]-N₆) involving metal template condensation between 1,2-diaminoethane, trichloromethane and dichloromethane, respectively, are reported. Formulation of [Cu₄(OTCE)(H₂O)₈]Cl₈ and [Cu₃(HCPD)(H₂O)₆]Cl₆ · 2H₂O and the ligand hydrochlorides OTCE · 8HCl and HCPD · 6HCl are supported by elemental analyses, conductivity measurements, and spectral studies. For a comparative cavity size effect on the stability constant, potentiometric measurements on the copper complexes of the generated macrocycles [15]-N₆ and [20]-N₈ and the structurally related larger macrocycle 1,3,6,8,11,13,16,18,21,23-decaaza-2,2,7,7,12,12,17,17,22,22-decachlorocyclopentacosane (DDCP, [25]-N₁₀, prepared recently) have been performed in aqueous solution at 25°C (μ = 0.1 M KNO₃). Very high stability constants obtained for reaction Cu²⁺ + A ? CuA²⁺ (A = ligand, log K = 20.51 and 25.87, respectively, for OTCE and DDCP systems) are a reflection on the folding of the ligand to provide a small cavity suitable for fitting of the copper ion. Further, a high equilibrium constant value for CuA²⁺ + Cu²⁺ ? Cu₂A⁴⁺ (OTCE system, log K = 14.59) or Cu₂A⁴⁺ + Cu²⁺ ? Cu₃A⁶⁺ (DDCP system, log K = 16.69) is due to suitable fitting of two and three copper ions in the 20-membered and 25-membered ring cavity of OTCE and DDCP, respectively.     

Effect of Temperature on Oxide Formation in Ligand-Deficient Cu|Cu(II), Ethylenediamine System

The influence of temperature on formation of oxide layers on copper electrode in solutions containing 0.01 M Cu(II), 0.005 M ethylenediamine, and 0.3 M K₂SO₄ as a supporting electrolyte at pH 5.3 is investigated. The rate of net process Cu + Cu²⁺ + H₂O Cu₂O + 2H⁺ proceeding under open-circuit conditions is supposedly controlled by interaction between copper electrode and Cu²⁺ aqua-ions. Well-defined voltammetric peak is observed at –0.75 V (SHE), the height of which may serve as a measure of Cu₂O formation rate. An activation energy and a formal rate constant of the process are found to equal 30 kJ mol^–1 and 0.17 s^–1.     

Protolytic properties of <Emphasis Type="Italic">DL</Emphasis>-alanyl-<Emphasis Type="Italic">DL</Emphasis>-methionine and its complexation in aqueous solutions and micellar solutions

Dissociation constants of DL-alanyl-DL-methionine have been determined in water and micellar solutions of surfactants (anionic sodium n-dodecyl sulfate, cationic cetylpyridinium chloride, and nonionic Brij 35). It has been established that CuA⁺ and CuH_–1A complexes are formed in water and micellar solutions of sodium n-dodecyl sulfate, while CuA⁺, CuH_–1A, and Cu_–2A^– complexes are formed in micellar solutions of cetylpyridinium chloride and Brij 35. Stability of the complexes depends on micelle surface charge and degrees of binding of individual chemical forms by a micellar pseudophase.     

Copper(II)–1,2-bis(thiocarbamoyl)hydrazine and copper(II)–(1-carbamoyl-2-thiocarbamoyl)hydrazine complexing in copper(II)hexacyanoferrate(II) gelatin-immobilized matrix systems

The complex formation that occurs in gelatin-immobilized copper(II)hexacyanoferrate(II) matrices upon contact with aqueous alkaline (pH 12.0) solutions of 1,2-bis(thiocarbamoyl)hydrazine, H₂NC(S)NHNHC(S)NH₂ and 1-carbamoyl-2-(thiocarbamoyl)hydrazine, H₂NC(O)NHNHC(S)NH₂ has been studied. The reaction of each of these ligands with copper(II) is preceded by the destruction of copper(II)hexacyanoferrate(II) in an alkaline medium to form a polymeric copper(II) hydroxide, which is involved in the subsequent copper(II)–ligand complex formation. In both Cu^II–N ligand systems, two complex compounds are formed; the water-insoluble Cu₂B₂(H₂O)₂ dimer and a water-soluble product of tentative composition [CuB(HB)]^– (H₂B=ligand).     

Study of some trinuclear copper(II) complexes involving catechol aldehyde and heteroaromatic nitrogen bases

Trinuclear copper(II) complexes of types [A¹CuL(CuCl₂)L · CuA¹] and [A¹Cu · L{Cu(A-A)}L · Cu · A¹](ClO₄)₂ have been studied, where L = 3,4-dihydroxybenzaldehyde and A-A = 2,2′-bipyridyl (A¹), 1,10-phenanthroline (A²) or 2-(2′-pyriyl)-benzimidazole (A³).     

Coordination behavior of 3,4-bis(2-pyridylmethylthio)toluene with copper(II) ions: Synthesis,structural characterization and reactivity,and DNA binding study of the dinuclear copper(II) complex

On reaction of different copper(II) salts with 3,4-bis(2-pyridylmethylthio)toluene (L) having neutral tetradentate NSSN donor set in different chemical environments, two mononuclear copper(II), one dinuclear copper(I) and one dinuclear copper(II) complexes, formulated as [Cu^II(L)(H₂O)₂](NO₃)₂ (1), [Cu^II(pic)₂] (2), [Cu^I₂(L)₂](ClO₄)₂ (3) and [Cu^II₂(L)₂Cl₂](ClO₄)₂ (4), respectively, were isolated in pure form [where pic = picolinate]. All the complexes were characterized by physicochemical and spectroscopic methods. The product of the reactions are dependent on the counter anion of copper(II) salts used as reactant and on the reaction medium. Complexes 1 and 4 were obtained with nitrate and perchlorate copper(II) salts, respectively. On the other hand, C–S bond cleavage was observed in the reaction of L with copper(II) chloride to form in situ picolinic acid and complex 2. Dinuclear complexes 3 and 4 were separated out when copper(II) perchlorate was allowed to react with L in methanol and in acetonitrile, respectively, under aerobic condition. The X-ray diffraction analysis of the dinuclear complex 3 shows a highly distorted tetrahedral geometry about each copper ion. Complex 4 is converted to 3 in acetonitrile in presence of catechol. The spectral study of complex 4 with calf thymus DNA is indicative of a groove binding mode interaction.     

Novel trinuclear copper(II) complexes with α,β-unsaturated carboxylates and imidazole

A MeOH solution of imidazole reacts with Cu₂A₄(H₂O)₂ [A = CH₂=CHCO^– ₂, CH₂=C(Me)CO^– ₂] to yield novel trinuclear copper(II) carboxylate complexes of general formula: Cu₃A₅(OH)(imH)₃ [(1) A=CH₂=CHCO^– ₂; (2) A = CH₂=C(Me)CO^– ₂; imH = imidazole]. The crystal structure of (2) has been determined. The geometry of one copper(II) atom is distorted trigonal bipyramidal, and the other two copper(II) atoms are distorted square-planar. The i.r. spectra show the presence of the absorption bands of both bidentate ₂-O,O and monodentate carboxylate ligands. The electronic reflectance spectra in the solid state suggest that the d–d transitions of complexes are in a trigonal bipyramidal ligand field and a square-planar ligand field. Room temperature X-band e.s.r. spectra of powdered samples with g _av = 2.140 for (1) and g _av = 2.092 for (2), indicate that there is no spin coupling between the copper(II) atoms.     

ESR and pH-potentiometric study of the mixed-ligand complex formation in the copper(II)-4-fluorosalicylic acid-N,N-diethylnicotinamide system: Structure and spectral properties of [Cu(4-fluorosalicylate)2(N,N-diethylnicotinamide)2(H2O)2] complex

EPR simulation method together with pH-potentiometry combined with UV-Vis spectrophotometry were used for the study of the ternary system 4-fuorosalicylic acid (HA)-N,N-diethylnicotinamide (B)-copper(II) in aqueous solution. The N,N-diethylnicotinamide ligand is a weak donor, its mixed-ligand complexes with 4-fluorosalicylate anions are more favoured. The number of coordinated N,N-diethylnicotinamide molecules increases with decreasing temperature: up to four ones were detected in the coordination sphere of copper(II) in frozen solutions. The formation of [CuH₋₁AB₂] and [CuH₋₁A] was detected by all methods at neutral pH. At lower pH values, [CuA₂B₂] and [CuB] become dominant, and this fact is in good agreement with [CuA₂B₂(H₂O)₂] crystals obtained from similar solutions. The structural unit of the [CuA₂B₂(H₂O)₂] complex consists of a copper(II) ion, which is monodentately coordinated by a pair of 4-fluorosalicylate anions and by a pair of N,N-diethylnicotinamide in trans positions in the basal plane, and by two water molecules in the axial positions of a tetragonal bipyramid.     

Physico-chemical studies on the chelation behaviour of acenaphthenequinone monothiosemicarbazone (AQTS) with some bivalent metal ions

Summary The stability constants of the chelates formed from acenaphthenequinone monothiosemicarbazone and magnesium(II), manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) or cadmium(II) have been determined pH-metrically in 75% v/v aqueous dioxan at various ionic strengths of NaClO₄ and at different temperatures. The method of Bjerrum and Calvin^{(1, 2)} as modified by Irving and Rossotti⁽³⁾, has been used to determine the ñ and pL values. The stability constants were calculated on an IBM 360 FORTRAN-IV computer patterned after that of Sullivanet al. ⁽⁴⁾ to give _n values using a weighted least squares method. The S_min, values were also calculated. The thermodynamic stability constant has been determined by extrapolating the log K₁ vs plot at zero ionic strength. The other thermodynamic functions have been calculated from the stability constants obtained for different temperatures at constant ionic strength. The bivalent metal stability sequence of AQTS chelates is in agreement with reported metal orders for other chelating reagents. The order of free energies and enthalpies of chelate formation for AQTS are: Mn²⁺2+2+2+>Zn²⁺.     

Molecular structures and ESR spectra of copper(ii) complexes with 2-hydroxypropiophenone acyldihydrazones

The dinuclear copper(ii) complexes with 2-hydroxypropiophenone acyldihydrazones (H₄L) having the composition [Cu₂L·mPy], where the L ligand contains the polymethylene chain with different lengths (from two to five units), were synthesized and studied. The crystal and molecular structures of the 2-hydroxypropiophenone adipoylhydrazone complex [Cu₂L·4Py]·Py were established by X-ray diffraction analysis. Copper atoms are 8.212 distant from each other, and their nearest environment has the tetragonal pyramidal geometry. The ESR spectra of solutions of the complexes based on acyldihydrazones of succinic, glutaric, and adipic acids contain seven HFS lines with the constant 40·10^–4 cm^–1 from two equivalent copper atoms. The spectra were interpreted as a result of the spin-spin exchange interaction of two unpaired electrons. An increase in the polymethylene chain length to five units prevents exchange interactions. The ESR spectrum of the complex with acyldihydrazone of pimelic acid contains a signal of four HFS lines with a _Cu = 73.4·10^–4 cm^–1, which is typical of mononuclear copper(ii) complexes.     

Ternary complex formation of copper(II) with 5-fluorosalicylate and 3-pyridylmethanol in aqueous solutions and solid state

The [CuA₂B₂] complex (A = 5-fluorosalicylate, B = 3-pyridylmethanol) – has been crystallized from the solutions with different initial component concentration ratios. For the first time a 1-D chain polymeric structure is described for such a system. The A ligand is coordinated through its carboxylate-oxygen in a monodentate manner, while B is forming ligand bridges between the copper(II) centers. The latter ligand binds with the non-deprotonated alcoholic OH to one and with the pyridyl-nitrogen to the other metal ion. Being a complex with potential biological activity it is of interest to study the ternary complex formation between copper(II), A and B in aqueous solution. Combined pH-potentiometric and spectrophotometric titrations were performed to obtain the composition and stabilities of the complexes. The formation of different ternary complexes was demonstrated both by the pH and absorbance effects. The [CuA₂B₂] complex dominates around pH 5 with the coordination of the carboxylic oxygens of two A ligands and pyridyl nitrogens of two B ligands. With increasing pH first the deprotonation of the phenolic-OH between pH 6 and 7 occurred leading to [CuH₋₁AB₂] complex. In alkaline pH range the formation of a mixed hydroxido species of composition [CuH₋₂AB]⁻ was proposed.     

Copper(II) complexes of tetradentate N2S2 donor sets: Synthesis,crystal structure characterization and reactivity

Two mononuclear and one dinuclear copper(II) complexes, containing neutral tetradentate NSSN type ligands, of formulation [Cu^II(L¹)Cl]ClO₄ (1), [Cu^II(L²)Cl]ClO₄ (2) and [Cu^II₂(L³)₂Cl₂](ClO₄)₂ (3) were synthesized and isolated in pure form [where L¹ = 1,2-bis(2-pyridylmethylthio)ethane, L² = 1,3-bis(2-pyridylmethylthio)propane and L³ = 1,4-bis(2-pyridylmethylthio)butane]. All these green colored copper(II) complexes were characterized by physicochemical and spectroscopic methods. The dinuclear copper(II) complex 3 changed to a colorless dinuclear copper(I) species of formula [Cu^I₂(L³)₂](ClO₄)₂,0.5H₂O (4) in dimethylformamide even in the presence of air at ambient temperature, while complexes 1 and 2 showed no change under similar conditions. The solid-state structures of complexes 1, 2 and 4 were established by X-ray crystallography. The geometry about the copper in complexes 1 and 2 is trigonal bipyramidal whereas the coordination environment about the copper(I) in dinuclear complex 4 is distorted tetrahedral.     

Crystal structures of Cu(II) complexes of pyridine-2,6-dithiocarbomethylamide

The crystal structures of three copper(II) complexes of pyridine-2,6-dithiocarbomethylamide (P DT A) were determined by X-ray crystallographic methods. The structure of the bromide CuP DT ABr₂ · H₂O (2) is isomorphous to the known crystal structure of the chloride CuP DT ACl₂ · H₂O (1). The iodide CuP DT AI₂ ·D M F (3) is non-isomorphous to the other two halogenides, but shows a very similar square-pyramidal 5-coordination of the copper atom. In contrast to the halogenides, the crystal structure of the nitrate CuP DT A (H₂O)₂ · (NO₃)₂ (4) shows a square planar metal coordination by theP DT A ligand and one water molecule. If one includes the second water molecule and one oxygen atom of a nitrate ion, the metal coordination becomes distorted octahedral.     

Synthesis, Spectral and Magnetic Characterisation of Copper(II) Dinuclear and Polynuclear Complexes with a Macrocyclic 34-Membered Hexaamine

34-Membered macrocyclic hexaamine containing two independent N₃ donor sets forms homodinuclear copper(II) complexes. Displacements of anions within the copper(II) chloride complexes occurred easily upon addition of different anions to the CuCl₂ complex. All new complexes were characterised by elemental analysis, IR, UV/VIS spectroscopy, and magnetic susceptibility measurements. Tetranuclear complexes indicate relation _Cu ^–1 vs. T in agreement with the Curie–Weiss law. A behaviour anomalous in relation to the phthalate complexes is shown by the [Cu₄L₂Cl₄(ox)₂] complex in which an antiferromagnetic coupling (J = - 53.9 cm^–1) between the Cu²⁺ ions through the C₂O ₄ ^2– bridge is observed.     

Complexation en solution aqueuse des ions magnesium(II), manganese(II), nickel(II), cuivre(II) et plomb(II) avec la s-carboxymethyl-l-cysteine: Complex formation of magnesium(II), manganese(II), nickel(II), copper(II) and lead(II) with S-carboxymethyl-L-cysteine in aqueous solution

Complex formation of magnesium(II), manganese(II), nickel(II), copper(II) and lead(II) with S-carboxymethyl-L-cysteine in aqueous solution.The complex formation between Mg(II), Mn(II), Ni(II). Cu(II), Pb(II) ions and S-carboxy-methyl-l-cysteine (H₂A) has been studied by measurement of pH at 25°C and constant ionic strength (1 M NaClO₄). Although no interaction occurs with Mg(II), this work provides evidence for a variety of complexes: MnA; CuHA⁺; CuA; CuA₂^2-; NiHA⁺; NiA; NiA₂^2-; PbHA⁺; PbA et PbA(OH)^-. The overall formation constants of all these species are computed and refined. The results allow the determination of the distribution of the complexes as a function of pH; some structural features of the metal complexes in solution are indicated.     

Crystal Structure of [(C2H5)4N]4Cu7Cl14O2: A Cu14Cl28O4 8− Cluster

The synthesis and crystal structure of a novel copper(ll) halide cluster, (Et₄N)₈Cu₁₄Cl₂₈O₄, is reported. The cluster anion Cu₁₄Cl₂₈O₄ ^8? can be Viewed as being formed by the dimerization of two Cu₇Cl₁₄O₂ ^4? fragments. The hypothetical precursor anion of this latter cluster, Cu₇Cl₁₅O₂ ^5? in tum can be viewed as being formed from. the known parent Cu₇Cl₁₄O₂ ^4? cluster anions by fusion of pairs across a common CuCI₃ face. The fusion and dimenzation processes cause substantial distortion of the trigonal bipyramidal coordmation geometry of the copper(II) ions in the parent cluster. For three of the copper(II) ions this Yields a 4+1 geometry distinct from either trigonal blpyramldal or square pyramidal. The dimerization of the two Cu₇ clusters forces a severe distortion upon one additional copper(II) ion, this time towards a tetrahedral geometry. The implications of these distortions for the catalytic properties reactivities and magnetic behaviour of the parent complex are discussed.     

Komplexbildung des Kupfer(II) mit Opioidpeptiden

Complex Formation of Copper(II) with Opioid Peptides Complex compounds of copper(II) with the neuropeptide enkephaline were detected as CuH_?(n?1)L + nLi⁺ ions by means of FAB mass spectrometry. Formation constants of proton and copper(II) complexes of four opioid peptides (L-I ? L-IV) were determined potentiometrically. Complexes with methionine-containing ligands show the highest stability. Under physiological pH values all brain-existent enkephaline may be bound by endogeneous copper provided that [Cu²⁺] > 10^?7 M.     

Metal-phenoxyalkanoic acid interactions—XXIII. Complexes of copper(II) with the phenoxyisobutyric acids. The crystal structures of tetra-μ-[2-methyl-2-(4-chlorophenoxy)propanoato-O,O′)]-bis[(2-aminopyrimidine)copper(II)] and two polyaquacopper(II) tri-μ-[2-methyl-2-phenoxypropanoato-O,O′]-bis[(2-methyl-2-phenoxypropanoato)copper(II)] polymorphs

The crystal structures of three copper(II) complexes with phenoxyisobutyric acid (PIBAH) and p-chlorophenoxyisobutyric acid (PCIBAH) have been determined by X-ray diffraction. Tetra-μ-[2-methyl-2-(4-chlorophenoxy)-propanoato-O,O′]-bis[2-amino-pyrimidine)copper(II)], [Cu₂(PCIBA)₄(2-aminopyrimidine)₂]₂ (1) is a centrosymmetric tetracar☐ylate bridged dimer [Cu⋯Cu, 2.689(2)Å] with the nitrogens of the 2-aminopyrimidine molecules occupying the axial positions [CuN, 2.198(7)Å]. Tetraaquacopper(II) tri-μ-[2-methyl-2-phenoxypropanoato-O,O′]-bis[(2-methyl-2-phenoxypropanoato(copper(II)], [Cu(H₂O)₄]²⁺] {[Cu₂(PIBA)₅]⁻}₂, (2), is a disordered precursor of the stable structure (3), [Cu(H₂O)₅]²⁺ {[Cu₂(PIBA)₅]⁻·4H₂O, consisting of centrosymmetric square planar [Cu(H₂O)₄]²⁺ cations and tris(car☐ylate)-bridged dimer anions [Cu⋯Cu, 2.85(1)Å] (2). The fourth position of each square planar dimer ‘end’ is occupied by a car☐ylate oxygen of a PIBA molecule which also provides the ether oxygen capping each axial dimer site [CuO, 2.15(4), 2.19(5)Å]. This completes a five-membered chelate ring. A symmetrical array of eight hydrogen bonds link the four waters of the [Cu(H₂O)₄]²⁺ cation to the car☐yl oxygens of both the capping PIBA ligands of the two dimeric anions. Structure (3) has essentially identical [Cu₂(PIBA)₅]⁻ dimer anions [Cu⋯Cu, 2.929(1)Å] and hydrogen-bonding interactions with the tetraaquacopper(II) cations. However, water molecules partially occupy the octahedral sites of these cations [CuO, 2.46(1)Å], as well as a number of lattice sites in the crystal.