Structure of the hexanuclear Cu(II) β-diketonate complex

The structure of the hexanuclear copper(II) β-diketonate complex with gfa (hexafluoroacetylacetone) and dpm (dipivalylmethanate) ligands was studied by low-temperature (T = 100 K) X-ray diffraction. Crystal data for Cu₆(gfa)₄(dpm)₄(OH)₄ [C₆₄H₈₄Cu₆F₂₄O₂₀]: a = 28.2364(7) Å, b = 12.8072(3) Å, c = 24.7199(7) Å, β= 115.900(1)°, V = 8041.5(4) ų, space group C2/m, Z = 4, d _calc 1.661 g/cm³. The coordination polyhedra of the copper atoms — squares and octahedra — are formed by the oxygen atoms of the gfa and dpm ligands and groups. In all cases, the Cu-O distances vary from 1.89 Å to 2.13 Å. The complexes follow the sites of the rhombohedral sublattice with the parameters a _c ≈ 14.4 Å and a _c ≈ 61.5°.     

DNA-binding and photocleavage studies of metallofluorescein–porphyrin complexes of zinc(II) and copper(II)

The DNA-binding behaviors of the fluorescein?Cporphyrinatozinc(II) complex Zn(Fl-PPTPP) (Fl-PPTPP?=?5-(4-fluoresceinpropyloxy)phenyl-10,15,20-triphenylporphyrin) and fluorescein?Cporphyrinatocopper(II) complex Cu(Fl-PPTPP) with calf thymus DNA (CT-DNA) were investigated by UV?CVis absorption titrations, fluorescence spectra, viscosity measurements, thermal denaturation and circular dichroism. The results suggest that both complexes interact with CT-DNA by intercalation. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated. Both complexes exhibit significant DNA cleavage activity, and singlet oxygen may play an important role in these reactions.     

Spectrophotometric study of stability constants of cimetidine–Ni(II) complex at different temperatures

Cimetidine, a histamine H₂-receptor, has a structure which enables it to act as a chelating agent. The formation of nickel(II) complex with cimetidine has been studied spectrophotometrically at an absorption maximum of 622 nm at different temperatures. The data show that nickel(II) and cimetidine combine in the molar ratio of 1:2. The stability constants of the complex were calculated to be 1.40–2.4 × 10⁸ by continuous variation method and 1.24–2.4 × 10⁸ by mole ratio method at 25 and 40 °C, respectively. The immediately formed complex shows stability with respect to time and temperature.     

Synthesis,crystal structure,thermal decomposition,and XPS studies of homo and heterotrinuclear Cu(II)–Cu(II)–Cu(II) and Cu(II)–Ni(II)–Cu(II) complexes obtained from salpn type ligands

In this study, a mononuclear CuL complex was prepared by the use of bis-N,N′-(salicylidene)-1, 3-propanediamine (LH₂) and Cu²⁺ ion. NiCl₂ and NiBr₂ salt were treated with this complex in dioxanewater medium and two new complexes [(CuL)₂NiCl₂(H₂O)₂] and [(CuL)₂NiBr₂(H₂O)₂)] with Cu(II)–Ni(II)–Cu(II) nucleus structure were obtained. In addition to this bis-N,N′-(2-hydroxybenzyl)-1,3-diaminopropane (L^HH₂) was prepared by the reduction of LH₂ with NaBH₄ in MeOH medium. The treatment of this reduced complex with Cu²⁺ ion resulted a complex [(CuL^H)₂CuCl₂] with a structure of Cu(II)–Cu(II)–Cu(II). The complexes prepared were characterized by the use of elemental analysis, IR spectroscopy, thermogravimetric and X-ray diffraction methods. The crystal structures of [(CuL)₂NiBr₂(H₂O)₂] (СIF file CCDC 1448402) and [(CuL^H)₂CuCl₂] (СIF file CCDC 1448401) complexes were elucidated. It was found that halogen ions are coordinated to terminal Cu²⁺ ions which are in a distorted square pyramid coordination sphere. It was determined that the central Cu(II), which joins terminal square pyramidal Cu(II), was coordinated only by the phenolic oxygens of the ligand while the central Ni(II) was coordinated by two phenolic oxygens of the organic ligand and two water molecules. These complexes were investigated by XPS and it was found that the terminal and central Cu²⁺ ions were different in Cu(II)–Cu(II)–Cu(II) complex. Also, the thermal degradation of the CuLH complex unit was observed to exothermic in contrast to the expectations.

     

DNA Hydrolysis by Homo- and Heteronuclear Cu(II)–Ni(II) Complexes of Two Diester-type Ligands

Summary. Nucleolytic activities of novel mononuclear Cu(II), homo- and heterodinuclear Cu(II)–Ni(II) complexes with two diester-type ligands were investigated on pCYTEXP by neutral agarose gel electrophoresis. The analyses of the cleavage products obtained electrophoretically indicate that the examined complexes induce very similar conformational changes on supercoiled DNA by converting supercoiled form to nicked form. At concentrations greater than 100M, the complexes possessed effective nucleolytic activities for 10min of incubation time. However, their nucleolytic activities did not increase significantly with longer periods of incubation. The pH-nucleolytic activity profiles of the complexes differed significantly. Metal complex induced DNA cleavage was also tested for inhibition by various radical scavengers. It could be proposed from the data that diffusible intermediate oxidants are not involved in these reactions or they are not necessary for DNA cleavage since none of antioxidants inhibited DNA cleaving activities of the complexes.     

DNA Hydrolysis by Homo- and Heteronuclear Cu(II)–Ni(II) Complexes of Two Diester-type Ligands

Nucleolytic activities of novel mononuclear Cu(II), homo- and heterodinuclear Cu(II)–Ni(II) complexes with two diester-type ligands were investigated on pCYTEXP by neutral agarose gel electrophoresis. The analyses of the cleavage products obtained electrophoretically indicate that the examined complexes induce very similar conformational changes on supercoiled DNA by converting supercoiled form to nicked form. At concentrations greater than 100M, the complexes possessed effective nucleolytic activities for 10min of incubation time. However, their nucleolytic activities did not increase significantly with longer periods of incubation. The pH-nucleolytic activity profiles of the complexes differed significantly. Metal complex induced DNA cleavage was also tested for inhibition by various radical scavengers. It could be proposed from the data that diffusible intermediate oxidants are not involved in these reactions or they are not necessary for DNA cleavage since none of antioxidants inhibited DNA cleaving activities of the complexes.     

Mössbauer spectroscopic study of an iron(III) complex with crown porphyrin

A complex of ⁵⁷Fe with 5-{4-[((4′-hydroxybenzo-15-crown-5)-5′-yl)diazo]phenyl}-10,15,20-triphenylporphyrin was studied by Mössbauer spectroscopy. The presence of signals of two types in the spectra (a doublet and an extended absorption band over a wide velocity range) suggests that the Fe atoms occupy two structurally different positions in this complex. The dependences of the doublet asymmetry on temperature and the angle between the normal to the sample plane and the γ-ray beam were studied. The isomer shift δ of the doublet in the temperature range from 360 to 5 K changes from 0.25 to 0.41 mm/s, while the quadrupole splitting remains virtually unchanged (Δ ≈ 0.65 mm/s). The relaxation-type absorption over a wide velocity range, the relative area of which strongly varies with temperature, can be described by a broad singlet with the following parameters: δ = 0.30–0.44 mm/s and Γ = 2.8–3.38 mm/s. According to the δ values, both signals are due to Fe(III) derivatives.     

Biophysical,spectroscopic and biochemical investigation of DNA–Cu(II)-GSH interactions

The interaction of DNA with Copper(II)-Glutathione (CuGSH) has been investigated by various biophysical methods. The interaction ratio of DNA and Copper(II)-Glutathione in solution phase has been determined spectrophotometrically and found to be 0.25. EPR spectroscopy and UV–Vis findings suggest that Cu(II)-Glutathione neither bound to the DNA bases covalently nor intercalated, this has further been substantiated by the determination of intrinsic binding constant (2.1 × 10²). Viscometric measurements also support this type of binding to DNA by Cu(II)-Glutathione. EPR studies and visible d–d spectra of CuGSH after interaction with DNA, suggested that Copper remained in the Copper(II) state. DNA conformations after interaction with Cu(II)-Glutathione has been determined spectroscopically. Circular dichroism studies revealed that the B conformation of DNA is changed to A after interaction with Cu(II)-Glutathione. This has further been substantiated by thin film IR (Infrared) studies.     

Microcalorimetric Evaluation of Precipitation in Cu–2Be–0.2Mg

Beryllium precipitation from the Cu-rich matrix in a Cu–2 mass% Be–0.2 mass% Mg alloy homogenized and quenched from 1073 K was studied by differential scanning calorimetry (DSC). The DSC traces showed two main exothermic effects, A and B, each comprising two subeffects: A₁ and A₂ , and B₁ and B₂ respectively. Effects A₁ and A₂ correspond to the precipitation of GP zones and subsequent overlapping and independent precipitation of the phase. Only at very low heating rates can be inherited from GP zones. Effects B₁ and B₂ correspond to heat evolved during transitions to the states with and phases, respectively. Heat effect A can be quantitatively described in terms of solid solubilities before and after precipitation, and of the precipitation heats of the phases involved. The heat content of the combined GP zone/ phase precipitation effect was proportional to the number of beryllium atoms precipitated, yielding an average value of 21 kJ mol^–1 beryllium for beryllium precipitation. It was shown that the phase arises from the combined transition from states with GP zones and phases, whereas arises from the transition of states with and phases. The apparent activation energies associated with GP zones and , and phases are 1.16±0.08, 1.18±0.07, 1.37±0.08 and 1.74±0.09 eV, respectively. These values are discussed in terms of the mobility of dissolved atoms related to the concentrations of excess vacancies and solute-vacancy complexes, and the direction of plate-like precipitate growth (either normal or perpendicular to the plate). It is inferred that the main roles of magnesium are to decrease the amount and rate of GP formation, to enhance the volume fraction of and to suppress the discontinuous precipitation of .This revised version was published online in November 2005 with corrections to the Cover Date.     

X-ray study of volatile Ni(II), Cu(II), and Pd(II) complexes of β-ketoimine pivalyltrifluoroacetone

Synthesis of volatile complexes based on -ketoimine pivalyltrifluoroacetone, C(CH₃)₃C(NH)CH₂COCF₃, is described. The general formula of the complexes is M(L)₂, where M = Cu, Ni, Pd. Complexes of this kind with Ni and Pd were obtained for the first time. The Cu and Pd complexes were found to be isostructural. A comprehensive crystal-chemical study showed that all structures are molecular and built of trans-complexes. The central atom has a square plane environment. The average M-O and M-N distances are nearly equal in all compounds: 1.84 , 1.92 , and 1.98 for Ni, Cu, and Pd complexes, respectively; the mean values of the O-M-N chelate angles are 93.4°, 91.9°, and 92.7°, respectively.Original Russian Text Copyright © 2004 by I. A. Baidina, G. I. Zharkova, N. V. Pervukhina, S. A. Gromilov, and I. K. IgumenovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 713–722, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis,structure and magnetism of a hydrogen-bond-linked three-dimensional network of a novel nickel(II)–cobalt(II)–nickel(II) complex containing a new macrocyclic mononuclear complex ligand

A novel trinuclear complex, [Co(NiL)₂(H₂O)₂](ClO₄)₂ · 2C₂H₅OH, was prepared by self-assembly using [NiL] as a new complex ligand; L is the dianion of dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate. The structure of the trinuclear complex was determined by X-ray crystallography. The Co^II ion is at the center of the trinuclear complex cation and occupies a distorted octahedral O₆ environment, approximating to O _h with a ⁴ T _1g ground state for Co^II that has an unquenched spin–orbit coupling reflected in the magnetic properties. Two Ni^II ions reside in completely same and slightly distorted square-planar N₄ coordination geometries. Co^II and each Ni^II are bridged by an oxamido group from one of the two macrocyclic ligands (L). O—H...O and ... interactions link the trinuclear fragments, perchlorate ions and C₂H₅OH molecules to form a three-dimensional supramolecular architecture.     

Electrocatalytic reduction of molecular oxygen at electrodes coated with a new cobalt(II)–platinum(II) bimetallic porphyrin

Cobalt(II) inserts into 5-(4-pyridyl)-10,15,20-(3,4-dimethoxyphenyl)porphyrin (1) by reaction of the porphyrin with the cobalt(II) acetate salt in refluxing N,N′-dimethylformamide solutions. When the porphyrin and the cobalt porphyrin are reacted with PtCl₂(DMSO)₂ in dichloromethane at ambient temperatures the platinum complex coordinates to the peripheral pyridyl group of the porphyrin. Roughened EPG electrodes coated with the cobalt(II)–platinum(II) bimetallic porphyrin, complex (4), show a 500?mV shift in the reduction of molecular oxygen in acidic media when compared to the bare electrode. Oxidation of the bimetallic porphyrin coated electrodes at 1.20?V versus saturated calomel electrode (SCE) results in an additional shift of ca 100?mV for the reduction of molecular oxygen when compared to the bimetallic porphyrin coated electrode prior to oxidation. In addition the oxidized surface shows the ability to reduce approximately 50% of the oxygen to water and the other 50% to hydrogen peroxide according to rotating disk electrode measurements.     

Ruthenium(II)–NNN complex catalyzed Oppenauer-type oxidation of secondary alcohols

Highly efficient Oppenauer-type oxidation of secondary alcohols to the corresponding ketones has been realized by means of the ruthenium(II) complex catalysts bearing a 2-(benzoimidazol-2-yl)-6-(3,5-dimethylpyrazol-1-yl)pyridine ligand. The oxidation reaction underwent in the presence of acetone as oxidant under mild conditions, reaching final TOF values up to 3960 h⁻¹. The hemilability of the ligand is attributed to the high catalytic activity of these Ru(II) complexes.     

Redox reactions of peroxo terpyridine complexes of Cu(II), Zn(II), and Cu(II)?Zn(II): A pulse radiolysis study

The reactions of e_aq⁻, CH₂OH·, (CH₃)₂COH·, CO, OH· and N₃· radicals with peroxo terpyridine complexes of Cu(II), Zn(II), and Cu(II) Zn(II) in aqueous solution were investigated by pulse radiolysis. The primary products from the reduction and oxidation of the macrocyclic complexes were assigned a radical nature by comparing their optical spectra with those of Cu(I), Zn(I), and Cu(III) species. Such metal–ligand radical products undergo disproportionation that does not lead to the formation of Cu(0) or colloidal copper. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 92–98, 2000     

Synthesis,characterization and DNA-binding properties of mixed porphyrin–polypyridyl ruthenium(II) complexes

Two mixed porphyrin–polypyridyl Ru^II complexes [Ru(bpy)₂(MPyTPP)Cl]Cl (1) and [Ru(phen)₂(MPyTPP)Cl]Cl ( 2 ) (bpy=2,2-bipyridine; phen=1,10-phenanthroline; MPyTPP=5-monopyridyl-10,15,20–triphenylporphyrin) have been synthesized and characterized by elementary analysis, e.s.–m.s., cyclic voltammetry and u.v.–vis. spectroscopy. The DNA-binding properties of these complexes were investigated by electronic spectra, c.d. spectra and viscosity experiments. The results suggested that both complexes (1) and (2) bind to DNA in an outside binding mode. At the same time, theoretical calculations applying the ab initio and the density functional theory (DFT) methods were also performed, and the results showed that there is no good planarity on the main ligand MPyTPP of these complexes, and there are rather great distortion angles (dihedral angles ca. 72°) between the porphrin ring and each of the 10-, 15-, 20-phenyl groups. This may be the reason why the complexes bind to DNA in an outside mode, instead of an intercalative mode.     

Complexes of Cu(I) and Pd(II) with (+)-camphor and (–)-cavrone thiosemicarbazones: Synthesis,structure, and cytotoxicity of the Pd(II) complex

CuLCl, CuL¹Cl, PdLCl₂, and PdL¹Cl₂ complexes [L and L¹ being (+)-camphor and (–)-carvone thiosemicarbazones, respectively] have been synthesized. The structure of binuclear [Pd₂L²²Cl₄] complex has been determined by means of X-ray diffraction. The L² ligand (dehydrogenated (–)-carvone thiosemicarbazone) is coordinated via the bridging S atom to two Pd atoms. The complexes of Cu(I) and Pd(II) presumably have polynuclear and binuclear structure, respectively. These facts are in good agreement with IR and NMR spectroscopy as well as mass spectrometry data which indicate the coordination of L and L¹ ligands via the S atom. The influence of L¹ and PdL¹Cl₂ on viability of the Hep2 cell line has been studied. The PdL¹Cl₂ complex is more cytotoxic than L¹ ligand.