Structure controlled self-assembly of Cu(II) salicylic aldehyde and aldimine derivative complexes

The order of self-assembled monolayers of Cu(II) salicylic aldehyde and aldimine complexes has been gradually changed by ligand substitution and the resulting nanostructures have been studied at the graphite/liquid interface using scanning tunneling microscopy.     

On Cu(Hg)/Cu(II) equilibria and reactions in aqueous sulphate solution

Combined thermodynamic and kinetic studies have revealed amalgam properties, solution activities, and diffusion data besides charge-transfer parameters and exchange rates for either step of the Cu(Hg)/Cu(II) electrode in aqueous solutions of xM CuSO₄+(0.5?x) M MgSO₄+H₂SO₄ (to pH about 2.5) at 25°C. The studies allow separation of mean ionic activities into convenient single-ion ones. The kinetic results demonstrate the consecutive two-step mechanism involved. Comparison is made to the solid Cu/Cu(II) electrode, and double-layer effects are discussed.     

Complexation of Cu(II) with cefotaxime in NaCl solution

Complexation of Cu²⁺ cations with anions of cefotaxime antibiotic (Cxm^–) was studied by pH-metric titration at 37°C in 0.15 mol/L NaCl background electrolyte. The formation of complex of composition CuCxm was revealed, the value of logβ(CuCxm) = 2.3 ± 0.2 was calculated. A computer model of the complex was calculated by DFT using B3LYP hybrid functional and LACV3P**++ basis set. According to calculation results, Cu(II) in the complex has CN = 4, close to square planar structure of coordination sphere, and coordinates Cxm^– through the oxygen atoms of the carboxylate, β-lactame, and amide groups, as well as through the nitrogen atom of the thiazole ring.     

On the structure of Zn(II) and Cu(II) cyanin complexes in aqueous solution

B3LYP/6-31++G(d,p) optimizations on models for the metal cyanin, Cy, complexes [MCy(H₂O) _n ]⁺, (M = Zn(II), Cu(II); n = 2, 3, 4) in aqueous solution indicate that 4 is the most favoured coordination number in both cases. SP -4 and T -4 geometries are nearly isoenergetic for the former, while SP -4 is the only one obtained for the latter. Anionic cyanin displays higher affinity for Cu(II) than for Zn(II) or Mg(II). The electron density reorganization of cyanin model accompanying the complexation process was analyzed by means of the quantum theory of atoms in molecules. This analysis reveals that: (1) the O4′–M bond is stronger than O3′–M; (2) anionic cyanin displays a dual character between 4′-keto-quinoidal and 3′,4′-dienolate resonance forms; (3) Cu(II) takes more electron density than Zn(II) from Cy^? and water ligands; (4) when the coordination number increases, each ligand (Cy^? or water) transfers less electron density; (5) complex formation modifies the electron density in all the atoms of the ligands, but the largest modifications are displayed within the AC bicycle of Cy^?; and (6) a third part of density lost by the Cy^? ligand is removed from hydrogens.     

Imidazolate bridged Cu(II)-Cu(II) and Cu(II)-Zn(II) complexes of a terpyridinophane azamacrocycle: a solution and solid state study

The dinuclear Cu2+ and Zn2+ as well as the mixed Cu2+-Zn2+ complexes of a 5,5'-pentaazaterpyridinophane ligand (L) are able to incorporate imidazolate (Im-) as a bridging ligand. The crystal structure of [Cu(2)L(Im)(Br)(H2O)](CF(3)SO(3))(2).3H2O (1) shows one copper coordinated by the three pyridine nitrogens of the terpyridine unit, one nitrogen of the imidazolate bridge (Im-) and one bromide anion occupying the axial position of a distorted square pyramid. The second copper atom is coordinated by the remaining imidazolate nitrogen, the three secondary nitrogens at the centre of the polyamine bridge and one water molecule that occupies the axial position. Magnetic measurements have been performed in the 2.0-300.0 K temperature range. Experimental data could be satisfactorily reproduced by using an isotropic exchange model H = -JS(1)S(2) with J = -52.3 cm(-1) and g = 2.09. Potentiometric studies have provided details of the speciation and stability constants for the mixed Cu2+-L-HIm, Zn2+-L-HIm (HIm = imidazole) and Cu2+-Zn2+-L-HIm systems. The apparent stability constant obtained at pH = 9 for the addition of imidazole to the dinuclear Cu2+ complexes is one of the highest so far reported (log K = 7.5). UV-Vis spectroscopy and paramagnetic NMR data show that imidazole coordinates to the Cu2+ ions as a bridging imidazolate ligand from pH 5 to 10. Electrochemical reduction of the Cu2+-Zn2+-L complex occurs in two successive one-electron per copper ion quasi-reversible steps. The formal potential of the Cu2+-Zn2+-L/Cu+-Zn2+-L couple is close to that of SOD. The IC50 values measured at pH 7.8 by means of the nitro blue tetrazolium method show significant SOD activity for the dinuclear Cu2+ complexes (IC50 = 2.5 microM) and moderate activity for the Cu2+-Zn2+ mixed systems (IC50 = 30 microM).     

A series of trinuclear Cu(II)Ln(III)Cu(II) complexes derived from 2,6-Di(acetoacetyl)pyridine: synthesis, structure, and magnetism

A series of trinuclear Cu(II)Ln(III)Cu(II) complexes with the bridging ligand 2,6-di(acetoacetyl)pyridine have been prepared by one-pot reaction with Cu(NO(3))(2).3H(2)O and Ln(NO(3))(3).nH(2)O in methanol. X-ray crystallographic studies for all the complexes indicate that two L(2)(-) ligands selectively sandwich two Cu(II) ions with the 1,3-diketonate entities and one Ln(III) ion with the 2,6-acetylpyridine entity to form a trinuclear CuLnCu core bridged by the enolate oxygen atoms. Cryomagnetic properties of the complexes are studied with respect to the electronic structure of the Ln ion.     

X-ray and solution structures of Cu(II) GHK and Cu(II) DAHK complexes: influence on their redox properties

The Gly‐His‐Lys (GHK) peptide and the Asp‐Ala‐His‐Lys (DAHK) sequences are naturally occurring high‐affinity copper(II) chelators found in the blood plasma and are hence of biological interest. A structural study of the copper complexes of these peptides was conducted in the solid state and in solution by determining their X‐ray structures, and by using a large range of spectroscopies, including EPR and HYSCORE (hyperfine sub‐level correlation), X‐ray absorption and ¹H and ¹³C NMR spectroscopy. The results indicate that the structures of [Cu^II(DAHK)] in the solid state and in solution are similar and confirm the equatorial coordination sphere of NH₂, two amidyl N and one imidazole N. Additionally, a water molecule is bound apically to Cu^II as revealed by the X‐ray structure. As reported previously in the literature, [Cu^II(GHK)], which exhibits a dimeric structure in the solid state, forms a monomeric complex in solution with three nitrogen ligands: NH₂, amidyl and imidazole. The fourth equatorial site is occupied by a labile oxygen atom from a carboxylate ligand in the solid state. We probe that fourth position and study ternary complexes of [Cu^II(GHK)] with glycine or histidine. The Cu^II exchange reaction between different DAHK peptides is very slow, in contrast to [Cu^II(GHK)], in which the fast exchange was attributed to the presence of a [Cu^II(GHK)₂] complex. The redox properties of [Cu^II(GHK)] and [Cu^II(DAHK)] were investigated by cyclic voltammetry and by measuring the ascorbate oxidation in the presence of molecular oxygen. The measurements indicate that both Cu^II complexes are inert under moderate redox potentials. In contrast to [Cu^II(DAHK)], [Cu^II(GHK)] could be reduced to Cu^I around ?0.62 V (versus AgCl/Ag) with subsequent release of the Cu ion. These complete analyses of structure and redox activity of those complexes gave new insights with biological impact and can serve as models for other more complicated Cu^II–peptide interactions.     

Crystal structure, spectroscopy and magnetism of trinuclear nickel(II), cobalt(II) complexes and their solid solution

Four new complexes [Ni₃(μ-L)₆(H₂O)₆](NO₃)₆·6H₂O (1), [Co₃(μ-L)₆(H₂O)₆](NO₃)₆·6H₂O (2), [Ni₃(μ-L)₆(H₂O)₄(CH₃OH)₂](NO₃)₆·4H₂O (3), [Co₃(μ-L)₆(H₂O)₄(CH₃OH)₂](NO₃)₆·4H₂O (4) (L = 4-amino-3,5-dimethanyl-1,2,4-triazole) were synthesized and structurally characterized by X-ray single-crystal diffraction. The structural analyses show that complex 1 and 2 are isomorphous; complex 3 and 4 are isomorphous. Four complexes all consist of the linear trinuclear cations ([M₃(μ-L)₆(H₂O)₆]⁶⁺ (M = Ni,Co) for 1 and 2; [M₃(μ-L)₆(H₂O)₄(CH₃OH)₂]⁶⁺ (M = Ni,Co) for 3 and 4), NO₃⁻ anions and crystallized water molecules. In the trinuclear cations, the central M(II) ions and two terminal M(II) ions are bridged by three triazole ligands. Other eleven solid solution compounds which are isomorphous with complex 3 and 4 were obtained by using different ratio of Ni(II) and Co(II) ions as reactants and ICP result indicates that ligand L has higher selectivity of Ni(II) ions than that of Co(II) ions. The magnetic analysis was carried out by using the isotropic spin Hamiltonian ? = −2J(?₁?₂ + ?₂?₃) (for complexes 1 and 3) and simultaneously considering the temperature dependent g factor (for complexes 2 and 4). Both the UV-Vis spectra and the magnetic properties of the solid solutions can be altered systematically by adjusting the Co(II)/Ni(II) ratio.     

Ternary complexes of cimetidine and phenobarbital with Cu(II) in methanolic solution

The formation constants of the binary complexes Cu(CM)²⁺ and Cu(CM) ₂ ²⁺ as well as those of the ternary complexes Cu(CM)L ⁺ and Cu(CM)₂ L ⁺ (CM=Cimetidine=N-Cyano-N-methyl-N[(5-methyl-1H-imidazol-4-yl)methyltioethyl]-guanidine; HL=Phenobarbital=5-ethyl-5-phenyl-barbituric acid) have been determined in 0.1 and 1.0 mol dm^–3 NaClO₄ methanol solutions at 25±0.2°C. The values of logX, log _stat.., and logK confirm the stability of the ternary complexes.

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Ternäre Komplexe von Cimetidin und Phenobarbital mit Cu(II) in methanolischer Lösung

Zusammenfassung Die Stabilitätskonstanten der binären Komplexe Cu(CM)²⁺ und Cu(CM) ₂ ²⁺ sowie die der ternären Komplexe Cu(CM)L ⁺ und Cu(CM)₂ L ⁺ (CM=Cimetidin=N-Cyan-N-methyl-N-[(5-methyl-1H-imidazol-4-yl)methylthioethyl]-guanidin; HL=Phenobarbitalum=5-Ethyl-5-phenyl-barbitursäure) wurden in 0.1 und 1.0M Lösungen von NaClO₄ in Methanol bei 25±0.2°C bestimmt. Die Werte von logX, log _stat. und logK bestätigen die Stabilität der ternären Komplexe.

     

Novel fluorescent sensor for detection of Cu(II) in aqueous solution

A novel fluorescent chemosensor based on aminonaphthol, which can selectively recognize copper(II) over other metal ions in aqueous solution within a broad pH span, was synthesized.     

Aqueous solution study of Cu(II) and Ni(II) complexes of macrocyclic oxa- and thia-containing trans-dioxo-tetraamines

Four macrocyclic trans-dioxo-tetraamines containing sulphur or oxygen as additional donors have been prepared: 1-oxa-3,14-dioxo-4,7,10,13-tetraazacyclopentadecane, 1-thia-3,14-dioxo-4,7,10,13-tetraazacyclopentadecane, 1-oxa-3,16-dioxo-4,8,11,15-tetraazacycloheptadecane and 1-thia-3,16-dioxo-4,8,11,15-tetraazacycloheptadecane. Their protonation as well as their metal binding properties with Cu²⁺ and Ni²⁺ have been determined at 25°C in 0.10 mol dm⁻³ KNO₃. The complexation process was investigated by potentiometric, calorimetric and UV/VIS-spectroscopic titrations. IR-spectroscopy was used to establish the involvement of the amido groups in the coordination. Oxidation of the complexes to the trivalent state of the metal ion was also investigated by cyclic voltammetry. Metal ion complexation promotes the deprotonation of the amide nitrogens, resulting in a neutral complex with four nitrogen donors and a MLH_-2 stoichiometry at pH 8. Additional complexes with stoichiometry ML and MLH_-1 were needed to describe the complexation in the pH range 2–11. Their stability constants were calculated. The presence of oxygen or sulphur donors as well as ring enlargement influence the complexation properties. The electronic spectra indicate rather distorted tetragonal coordination geometries for the Cu(II)-complexes. The Ni(II)-complexes are all square–planar with the exception of an equilibrium between a square–planar and an octahedral form for NiL¹H₋₂. All complexes are easily but irreversibly oxidized to the trivalent state of the metal ion.     

On the tri-n-octylammonium chloro complexes of Cu(II), Zn(II) and Co(II) in benzene solution

Extracts with tri-n-octylammonium chloro complexes of Cu(II), Zn(II) and Co(II) of various compositions, including the N-deuterated compounds, were prepared and investigated by IR spectroscopy and conductivity measurements. Besides the well-known 2:1-complexes (TOAH⁺)₂MCl₄^2?, for which new assignments of νNH frequencies are given, complexes with a stoichiometric ratio TOA:M > 2 were found. Their cations contain the groups (TOAH …Cl…HTOA)⁺ and TOAH⁺ and they are supposed to be 3:1-complexes (TOAH…Cl…HTOA)⁺TOAH⁺MCl₄^2?. The IR spectrum of the 1:1-complex TOAH⁺CuCl_3? is given. The occurrence of the analogous 1:1-complex TOAH⁺ZnCl_3? could not be detected under the preparative conditions used.     

Magnetic,epr and SOD studies of some Cu(II)-Cu(II), Cu(II)-Ni(II) and Cu(II)-Zn(II) imidazolate bridged complexes

Magnetic, spectroscopic and superoxide dismutase activity of imidazolate bridged [(Salala)Cu-Im-Cu(Salala)]Na, [(Salala)Cu-Im-Zn(Salala)]Na and [(Salala)Cu-Im-Ni(Salala)]Na (Salala=Salicyledenealiniate, Im=Imdiazolate) are described. The epr and electronic spectra of related mononuclear complexes, viz., [(Salala)Cu-OH(2)] and [(Salala)Cu-ImH] also described. Appearance of a half-field signal in polycrystalline and decrease in mu(eff) per copper(II) ion indicate super exchange coupling between copper(II) ion in [(Salala)Cu-Im-Cu(Salala)]Na binuclear complex. A pH-dependent epr and UV-vis study of 50% aqueous DMSO solution of binuclear complexes suggest that the complexes are stable in narrow pH range.     

L-半胱胺尾式卟啉铜(II)修饰金电极检测苯酚

将制备的L-半胱胺卟啉铜(II)(CuL)配合物自组装在Au电极表面,获得电化学苯酚传感器(CuL/Au)。在pH 7.0的磷酸盐缓冲液(PBS)中于-0.4 V~0.5 V(vs.SCE)电位范围内有一对氧化还原峰,峰电位分别为Epa=0.09 V和Epc=-0.06 V。实验结果表明CuL能够催化氧化苯酚,通过产物在电位0.1 V下的电化学响应对苯酚进行测定。该电极对苯酚表现出快速的响应(响应时间<10 s)。传感器对苯酚的测定具有较宽的线性范围(5.0×10-7mol.L-1~2.5×10-4mol.L-1),检出限为2.0×10-7mol.L-1。该电极用于地表水中苯酚含量检测,并与标准方法4-氨基安替比林分光光度法作了对照,结果满意。     

Separation of Ga(III) from Cu(II), Ni(II) and Zn(II) in aqueous solution using synthetic polymeric resins

Poly (acrylamide-acrylic acid-dimethylaminoethylmethacrylate), p(AM-AA-DMAEM) and Poly(acrylamide-acrylic acid)-ethylenediaminetetracetic acid disodium, p(AM-AA)-EDTANa₂ were prepared by gamma radiation-induced template polymerization technique and used for the separation of Ga (III) from Cu (II), Ni (II), and Zn (II) in aqueous media. The effect of pH and contact time on the separation process was studied. The optimum pH value for the separation process is 3–3.5. The result shows that Ga (III) is first extracted while Cu (II), Ni (II) and Zn(II) are slightly extracted at this pH value. The recovery of metals using HCl, HNO₃ and H₂SO₄ has been studied. The resins may be regenerated using 2M HCl solutions.      

O and N NMR studies of the Co(II), Cu(II) and Mn(II) complexes of glycine in aqueous solution

The ¹⁷O and ¹⁴N paramagnetic relaxation rates and chemical shifts of glycine as well as of water, in aqueous solutions of Co(II), Cu(II), and Mn(II) were measured as a function of pH, temperature and metal ion concentration; the relaxation results were fitted to a theoretical equation linking the Swift-Connick equation to the stability constants of all major complexes in equilibrium. As a result, the stability constants of all major complexes were determined, and from the temperature-dependent measurements the thermodynamic parameters for some of these complexes were also calculated. In addition to the bidentate complexes ML⁺, ML₂ and ML₃⁻, monodentate complexes of the type MHL²⁺ and M(HL)₂²⁺, mixed complexes of the type MHL₂⁺ and MHL₃ were also considered. In the case of the Cu(II)-glycine system at pH> 12 two additional species were considered, namely ML₂(OH)⁻ and ML₂(OH)₂²⁻, suggested by the drastic reduction of the paramagnetic broadening in that pH range.     

O and N NMR studies of the Co(II), Cu(II) and Mn(II) complexes of -proline in aqueous solution

The ¹⁷O and ¹⁴N paramagnetic transverse relaxation time and chemical shift of proline as well as of water, in aqueous solutions of Co(II), Cu(II) and Mn(II) were measured as a function of pH, temperature, and metal ion concentration. The relaxation results were fitted to a theoretical equation linking the Swift-Connick equation to the stability constants of the major complexes in equilibrium. Stability constants for the major complexes of the three ions in this work were determined, along with thermodynamic parameters for some of the complexes. Two complexes of Co(II) were detected directly by ¹⁷O NMR at basic pH, and were assigned to CoPrO₂ and CoPro₃⁻. The hyperfine coupling constant for these two complexes, A/h, was determined directly from the isotropic shift and was found to be −0.63 and −0.31 MHz, respectively. CoPrO₂ could be detected in the pH range 6–12, for Co(II) concentrations greater than 0.04 M, and its chemical shift was around 700 ppm downfield from free proline, at 300 K. CoPro₃⁻ was detected only at pH 11, in the temperature range 275–284 K, with a chemical shift of 390 ppm downfield from free proline.     

Assembly of cyano-bridged Cu(II)/Cu(II) and Cu(I)/Cu(II) compounds obtained by controlled ration of cyanide

One reaction system of Cu²⁺, dipn, and CN⁻ with two different molar ratio sets of 1:1:5, and 2:1:8 produced two compounds 1 [Cu^II(dipn)][Cu^II(CN)₄], and 2, respectively (dipn = dipropylenetriamine). Their structures were determined by X-ray crystallography. Compound 2 is built from Cu(I) and Cu(II) centers, which are bridged by cyanide groups and metal-metal bonds. The magnetic properties of 1 and 2 were investigated in 2-300 K. Compound 1 exhibits an antiferromagnetic exchange interaction between copper(II) ions mediated by cyano-bridges.     

Mn(II) and Cu(II) complexes of a dithiadiazolyl radical ligand: monomer/dimer equilibria in solution

Complexes of the 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl radical bidentate ligand with bis(hexafluoroacetylacetonato)manganese(II) and with bis(hexafluoroacetylacetonato)copper(II) have been prepared. Unlike the previously reported cobalt(II) complex, these complexes form dimers via intermolecular S...S contacts in the solid state. The spectroscopic and magnetic properties of these species in the solid state and in solution are reported and compared to the previously reported Co(II) complex, with emphasis on the elucidation of the a monomer/dimer equilibrium in the solution. The electrochemical properties of these species in solution are also presented and discussed.     

Molecular cube of Re(II) and Mn(II) that exhibits single-molecule magnetism

A pseudocubic, paramagnetic cluster of ReII and MnII, [{MnCl}4{Re(triphos)(CN)3}4], has been prepared, and its magnetic properties have been investigated. Antiferromagnetic coupling is observed between the "S = 1/2" ReII and S = 5/2 MnII centers resulting in an effective S = 8 ground state. AC susceptibility studies reveal that the molecule is a single-molecule magnet with an effective barrier for magnetization reversal of Ueff = 8.8 cm-1.