Binuclear metal complexes. 59. Synthesis and magnetism of dicopper(II) and copper(II)-nickel(II) complexes with N,N′-ethylenedisalicylamidatocuprate(II)

The complexes [Cu(samen)Cu(L)] and [Cu(samen)Ni(L)₂] (Lbpy, phen) have been synthesized by the reaction of sodium N,N′-ethylenedisalicylamidatocuprate(II) pentahydrate (Na₂- [Cu(samen)]·5H₂O), a divalent metal ion, and 2,2′- dipyridyl or 1,10-phenanthroline. Cryomagnetic data for the CuCu complexes did not fit the Bleaney- Bowers equation; but the data did fit a modified Bleaney-Bowers equation

with a large negative J and a significant negative θ, suggesting that a considerable magnetic interaction operates between essentially planar [Cu(samen)Cu(L)] molecules. The magnetisms of the CuNi complexes were well interpreted in terms of the susceptibility equation based on the Heisenberg model. An antiferromagnetic spin-exchange interaction (J= −13∼−14 cm⁻¹) was suggested between the metal ions.     

Tabanidae (Diptera) of State of Maranhão, Brazil II. Description of Esenbeckia (Esenbeckia) rafaeli, sp. nov

Esenbeckia (Esenbeckia) rafaeli, sp.nov. is described and figured from nine specimens collected in Carolina, state of Maranh?o, Brazil. The new species is compared with the species Esenbeckia (Esenbeckia) laticlava Wilkerson & Fairchild, 1983; Esenbeckia (Esenbeckia) bitriangulata Lutz & Castro, 1935 e Esenbeckia (Esenbeckia) enderleini Kr?ber, 1931.     

Immobilization of β-galactosidase (K. lactis) on solid phase Ni(II)-chelate

Summary Ni(II)-iminodiacetate-agarose achieved a near quantitative adsorption of -galactosidase (Kluyveromices lactis) with a yield of 96% of activity applied. A high percentage (90%) of -galactosidase activity was preserved after immobilization on the solid phase. The insoluble derivative could be used for lactose hydrolysis either in solution or in whey permeate.     

Synthesis, Characterization and Antitumor Studies of Mn(II), Ni(II), Cu(II) and Zn(II) Complexes of N-Nicotinoyl-N′-o-Hydroxythiobenzhydrazide

A new ligand N-Nicotinoyl-N-o-hydroxythiobenzhydrazide (H₂Notbh) forms complexes [Mn(Notbh)(H₂O)], [M(Notbh)] [M=Ni(II) Cu(II) and Zn(II)] which were characterized by various physico-chemical techniques. All the metal complexes were observed to inhibit the growth of tumor in vitro, whereas, ligand did not. In vivo administration of these complexes resulted in prolongation of survival of tumor bearing mice. Tumor bearing mice administered with metal complexes showed reversal of tumor growth associated induction of apoptosis in lymphocytes. The paper discusses the possible mechanisms and therapeutic implication of the H₂Notbh and its metal complexes in tumor regression and tumor growth associated immunosuppression.     

Synthesis and characterization of β-diketiminate germanium(II) and tin(II) bromides

The equimolar reaction of a β-diketiminate lithium salt LLi(OEt₂) [L = HC(CMeNAr)₂; Ar = 2,6-iPr₂C₆H₃] with either GeBr₂ or SnBr₂ in diethyl ether affords the synthetically useful monomeric β-diketiminate-element halides LGeBr (1) and LSnBr (2), respectively. Both are soluble in hydrocarbon solvents, stable in inert atmosphere, and have been characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction analysis.     

Complexes of Co(II), Ni(II), Cu(II) and Zn(II) with 3′AMP and 2′AMP

Derivatives of Co(II), Ni(II), Cu(II) and Zn(II) with 3′AMP and 2′AMP were synthesized and characterized by IR UV-Vis and fluorescence spectroscopy. There seems to be bonding of the metal ion to the base in all cases. The activation test, using the complexes as allosteric labels, was carried out with rabbit muscle glycogen phosphorylase b, but the enzyme was not activated, confirming that the phosphate group must necessarily be bonded to position 5′ of the ribose in order to activate this enzyme.     

Dicyanamido-metal(II) complexes. Part 4: Synthesis, structure and magnetic characterization of polynuclear Cu(II) and Ni(II) complexes bridged by μ-1,5-dicyanamide

The one pot aqueous reaction of M(ClO₄)₂ (M = Cu²⁺ or Ni²⁺) with N-methylbis[2-(2-pyridylethyl)]amine (MeDEPA) and N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethylenediamine (bpmen) and 1,4,7,10-tetraazacyclododecane (cyclen) in presence of sodium dicyanamide (Nadca) yielded dicyanamido-bridged polynuclear complex {[Cu(MeDEPA)(μ-1,5-dca)]ClO₄}_n (1), and two dinuclear complexes [Cu₂(bpmen)₂(μ-1,5-dca)]₂(ClO₄)₅dca (2) and [Ni(cyclen)(μ-1,5-dca)]₂(ClO₄)₂ (3). These complexes were characterized by IR and UV-Vis spectroscopy. Room temperature single-crystal X-ray studies have confirmed that the Cu(II) centers in 1 and 2 adopt geometries that are more close to trigonal bipyramidal (TBP) in 1 and close to square pyramidal (SP) in 2, whereas in 3, the Ni(II) centers are located in octahedral environment with doubly bridged μ-1,5-dca bonding mode. The intermolecular M···M distances in these complexes are in the range of 7.3-8.6 Å. Variable temperature magnetic susceptibility studies have confirmed that the dca-bridges mediate very weak antiferromagnetic interaction between the M(II) centers with J values of −0.35, −0.18 and −0.43 cm⁻¹ for 1, 2 and 3, respectively. The results are compared and discussed in the light of other related bridged μ-1,5-dca Cu(II) and Ni(II) complexes.     

Speciation of binary complexes of Co(II), Ni(II) and Cu(II) with L-aspartic acid in propylene glycol–water mixtures

Abstract

Speciation of binary complexes of Co(II), Ni(II) and Cu(II) with L-aspartic acid in (0-60% v/v) propylene glycol-water mixtures was studied pH metrically at 303.0±0.1 K and at an ionic strength of 0.16 mol L^-1. The binary species refined were ML, ML₂, ML₂H₂, ML₂H₃ and ML₂H₄. The stabilities of the complexes followed the Irving-Williams order i.e.Co(II) <Ni(II) < Cu(II). The linear variation of stability constants as a function of dielectric constant of the medium indicated the dominance of electrostatic forces over non-electrostatic forces. Some species were stabilised due to electrostatic interactions and some were destabilised due to the decreased dielectric constant. The order of ingredients influencing the magnitudes of stability constants due to incorporation of errors in their concentrations was alkali > acid > ligand > metal. Equilibria for the formation of binary complexes were proposed based on the forms of the ligand and their existence at different pH values.     

Structural diversity of neutral bis-(β-iminoaldehyde) complexes of nickel(II)

Series of Ni^II and Cu^II complexes with dianionic [N₂O₂] ligands were synthesized and characterised applying spectroscopic and X-ray diffraction techniques. The ligands were obtained by 1:2 condensation of ethylene- and propylenediamine with malonic aldehyde derivatives (R² = H, R¹ = H or OCH₃). Although the molecular formulae of the complexes are quite similar, the X-ray investigations have proved a significant structural diversity in the solid state. Among others, we found some simple nearly planar molecules stacked in the crystal lattice with electron density of six-membered rings delocalised over the chelate rings as well as some very complex polymeric or nickel acetate bridged trinuclear complexes. The coordination of the nickel ion by surrounding oxygen and nitrogen atoms is square-planar in the simplest case and octahedral in the most complex one. Small topological differences in similar molecules generate completely different crystal structures.From magnetic studies, a small, negative value of J obtained confirms the occurrence of weak antiferromagnetic interactions between the Ni^II ions in polymeric chain of the propylenediamine dialdehyde substituted derivative.     

pH-dependence of the specific binding of Cu(II) and Zn(II) ions to the amyloid-β peptide

Metal ions like Cu(II) and Zn(II) are accumulated in Alzheimer's disease amyloid plaques. The amyloid-β (Aβ) peptide involved in the disease interacts with these metal ions at neutral pH via ligands provided by the N-terminal histidines and the N-terminus. The present study uses high-resolution NMR spectroscopy to monitor the residue-specific interactions of Cu(II) and Zn(II) with (15)N- and (13)C,(15)N-labeled Aβ(1-40) peptides at varying pH levels. At pH 7.4 both ions bind to the specific ligands, competing with one another. At pH 5.5 Cu(II) retains its specific histidine ligands, while Zn(II) seems to lack residue-specific interactions. The low pH mimics acidosis which is linked to inflammatory processes in vivo. The results suggest that the cell toxic effects of redox active Cu(II) binding to Aβ may be reversed by the protective activity of non-redox active Zn(II) binding to the same major binding site under non-acidic conditions. Under acidic conditions, the protective effect of Zn(II) may be decreased or changed, since Zn(II) is less able to compete with Cu(II) for the specific binding site on the Aβ peptide under these conditions.     

X-ray absorption spectroscopic analysis of Fe(II) and Cu(II) forms of a herbicide-degrading α-ketoglutarate dioxygenase

 The first step in the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by Ralstonia eutropha JMP134 is catalyzed by the α-ketoglutarate (α-KG)-dependent dioxygenase TfdA. Previously, EPR and ESEEM studies on inactive Cu(II)-substituted TfdA suggested a mixture of nitrogen/oxygen coordination with two imidazole-like ligands. Differences between the spectra for Cu TfdA and α-KG- and 2,4-D-treated samples were interpreted as a rearrangement of the g–tensor principal axis system. Herein, we report the use of X-ray absorption spectroscopy (XAS) to further characterize the metal coordination environment of Cu TfdA as well as that in the active, wild-type Fe(II) enzyme. The EXAFS data are interpreted in terms of four N/O ligands (two imidazole-like) in the Cu TfdA sample and six N/O ligands (one or two imidazole-like) in the Fe TfdA sample. Addition of α-KG results in no significant structural change in coordination for Cu or Fe TfdA. However, addition of 2,4-D results in a decrease in the number of imidazole ligands in both Cu and Fe TfdA. Since this change is seen both in the Fe and Cu EXAFS, loss of one histidine ligand upon 2,4-D addition best describes the phenomenon. These XAS data clearly demonstrate that changes occur in the atomic environment of the metallocenter upon substrate binding. Received: 3 July 1998 / Accepted: 13 October 1998     

Preparation and characterization of oxovanadium(IV), acetatomanganese(III), chloroiron(III), nickel(II), copper(II), zinc(II) and palladium(II) complexes of 3,3′-(1,2-phenylenediimino)diacrolein

The oxovanadium(IV), acetatomanganese(III), chloroiron(III), nickel(II), copper(II), zinc(II) and palladium(II) of 3,3′-(1,2-phenylenediimino)diacrolein were prepared and investigated by means of mass, electronic, vibrational, NMR and ESR spectroscopy as well as magnetic susceptibility measurements. The acetatomanganese(III) and chloroiron(III) complexes were confirmed to be of high spin type. The absorption bands appearing in the energy range greater than 23 000 cm⁻¹ were attributed to π→π^* transitions within a ligand molecule and charge- transfer transitions from metal to ligand. The metal complexes assume the square-planar configuration type since the ligand-field bands were detected in the 12 700–18 500 cm⁻¹ region. Strong bands appearing at 1601 and 1627 cm⁻¹ were assigned to the CC and CO stretching vibrational modes, respectively, and were shifted to lower frequency upon metal-coordination. A VO stretching band was observed at 982 cm⁻¹ for the oxovanadium(IV) complex and a CO stretching band was observed at 1547 cm⁻¹ for the acetatomanganese(III) complex. Upon complex formation the amine proton signal is found to vanish and the aldehydic methine proton signal in the lowest field is shifted upfield for the nickel(II), zinc(II) and palladium(II) complexes. ¹³C NMR spectra support the coordination structure of the complexes which is revealed by ¹H NMR spectra. As judged by the spin Hamiltonian parameters, the oxovanadium(IV) complex is of a square- planar type with an unpaired electron in the d_xy orbital and the copper(II) complex assumes a distorted square-planar coordination due to the presence of five- and six-membered chelate rings with an unpaired electron in the d_x2−y2 orbital.     

Ligand substitution reactions of bis(μ-acetato)dichlorodicarbonyldiiridium(II)

Seven diiridium(II) complexes were synthesized by ligand substitution reactions of [Ir₂(μ-O₂CMe)₂Cl₂(CO)₂] (1) and [Ir₂(μ-O₂CMe)₂Cl₂(CO)₂(py)₂] (2).The reaction of 2 with the silver salt of a less coordinating anion, AgSbF₆, gave a cationic complex [Ir₂(μ-O₂CMe)₂Cl(CO)₂(py)₃]SbF₆ (3).A tricarbonyl cationic complex [Ir₂(μ-O₂CMe)₂(CO)₃Cl(py)₂]SbF₆ (4) was obtained under a CO atmosphere.Complex 2 reacted with AgO₂CCF₃ to give [Ir₂(μ-O₂CMe)₂Cl(O₂CCF₃)(CO)₂(py)₂] (5) in toluene.[Ir₂(μ-hiq)₂(CO)₂Cl₂] (Hhiq = 1-hydroxyisoquinoline, 6) was synthesized by the bridging-ligand substitution of 1 with Hhiq.Its axial adducts [Ir₂(μ-hiq)₂Cl₂(CO)₂L₂] (L = Mepy (4-methylpyridine), 7 or PPh₃, 8) were synthesized by addition of the ligands to a suspension of 6.In the structures of 7 and 8, two iridium atoms are bridged by two hiq ligands in a head-to-tail arrangement.The reaction of 1 with Hmhp (2-hydroxy-4-methylpyridine) led to triply bridged [Ir₂(μ-mhp)₃(CO)₂Cl(Hmhp)] (9).In complex 9, all the mhp ligands bridge between the Ir atoms in a head-to-head manner.The Ir-Ir distances of 3, 4, 5, 7 and 8 are 2.6047(7), 2.6216(9), 2.5899(9), 2.5933(5) and 2.634(2) Å, respectively, which are similar to those observed in[Ir₂(μ-O₂CMe)₂Cl₂(CO)₂L₂]. The Ir-Ir distance of 2.5512(4) Å in 9 is shorter than in the other complexes.     

Free metal ion depletion by “good's” buffers: II. N-(2-acetamido)-2-aminoethanesulfonic acid (ACESH): Complexes with Calcium(II), Magnesium(II), Manganese(II), Cobalt(II), Zinc(II), Nickel(II), and Cooper(II)

Potentiometric, visible, and infrared studies of the complexation of N-(2-acetamido)-2-aminoethanesulfonic acid (ACESH) by Ca(II), Mg(II), Mn(II), Co(II), Zn(II), Ni(II), and Cu(II) are reported. Ca(II), Mg(II), and Mn(II) were found not to complex with ACES^?, while Co(II), Zn(II), Ni(II), and Cu(II) were found to form 2:1, ACES^? to M²⁺, complexes, and [Cu(ACES)₂] was found to undergo stepwise deprotonation of the amide groups to form [Cu(H_?1ACES)₂^2?]. Formation (affinity) constants for the various metal complexes are reported, and the probable structures of the various metal chelates in solution are discussed.     

Synthesis, characterization and antitumor studies of N-aroyl-N′-thioaroylhydrazines and their Co(II), Ni(II), Cu(II) and Zn(II) complexes

N-Salicyloyl-N-p-hydroxythiobenzohydrazide (H₂STPH) and N-benzoyl-N-thiobenzohydrazide (H₂BTBH) and their Co(II), Ni(II), Cu(II) and Zn(II) complexes were prepared and characterized by physicochemical studies. IR and NMR spectral studies imply dibasic tetradentate behaviour of the ligands bonding through `thiolato' sulfur, enolic oxygen and the two hydrazinic nitrogens in a polymeric fashion. The electronic spectra indicate [Ni(STPH)(H₂O)₂], [Co(STPH)(H₂O)₂] to be distorted octahedral while [Cu(BTBH)] has a square-planar geometry. In vitro antitumor results of the ligand and the complexes on P-815 (murine mastocytoma) and L-929 (murine fibroblast) indicate that these compounds show significant inhibition of ³H-thymidine and ³H-uridine incorporation in DNA and RNA, respectively, in these tumor cells at dose levels of 1, 2.5 and 5 g cm^–3. Antitumor studies suggest that [Cu(BTBH)] has significant dose dependent inhibitory effect on DNA synthesis. In vivo administration of [Cu(BTBH)] and [Ni(STPH)(H₂O)₂] resulted into prolongation of life span of Dalton's Lymphoma (DL) bearing mice.     

Additional characterization of the two oxygen-containing compounds formed by the interaction of phthalocyaninatoiron(II) and dioxygen. Reproducible synthesis of the species isomorphic with the α form of Fe(II)Pc

The two compounds obtained by the interaction in solution of Fe(lI)Pc with O₂, presently considered two crystalline modifications of the μ-oxo dimer of Fe(III)Pc, are further characterized by visible absorption, XPS and Mössbauer spectra. The results stress the difference between the solid state properties of the two Fe(III) compounds.The behaviour of Fe(II)Pc and the two oxidized compounds in some chlorinated and non-chlorinated solvents, at different temperatures in the presence and absence of O₂, is reported. It is seen that heating the two Fe(III) products in 1-chloronaphthalene, or dimethylformamide, in vacuum sealed tubes, gives as a final product βFe(II)Pc. However, the same procedure in chlorobenzene or nitrobenzene yields, in a reproducible way, the pure oxygen-containing species which is isomorphic with αFe(II)Pc. Until now this product was only obtained in a fortuitous manner.     

Stabilization of a hydrated ketone by metal complexation. The crystal and molecular structures of bis-2,2′,N,N′-bipyridyl ketone-hydrate nickel(II) sulfate,copper(II) chloride and copper(II) nitrate

The crystal structure of the complexes (I)Ni[C₁₁N₈N₂(OH)₂]₂SO₄, (II) Cu[C₁₁H₈N₂(OH)₂]₂Cl₂· 4H₂O and (III) Cu[C₁₁H₈N₂(OH)₂]₂(NO₃)₂·2H₂O have been determined by three-dimensional X-ray analysis methods. Crystal data are: (I), monoclinic, space group C2/c, Z = 4, a = 19.666(4), b = 7.994(2), c = 16.045(6) /rA, /gb = 111.231(9)°, (II), monoclinic, space group C2/c, Z = 4, a = 14.504(4), b = 12.333(8), c = 14.630(3) Å, /gb = 90.92°; and (IIl), monoclinic, space group P2₁/n, Z = 2, a = 7.601(5), b = 11.977(4), c = 14.463(6) Å, β = 93.10(8)°. These structural investigations clearly demonstrate that in each case hydration occurs across the ketone double bond in the ligand and that the resulting hydroxyl group coordinates to the metal. Two di-2-pyridyl ketone ligands are thus bonded to the metal atom in a tridentate fashion. In the nickel complex (I), all six coordination interactions appear to have approximately the same strength. However, in the copper complexes (II) and (III), the pyridyl nitrogens are strongly coordinating to the metal in the equatorial plane, while the hydroxyl groups are more weakly coordinating in the axial direction. The metal to ligand bond distances are: (I) d_Ni−O = 2.098(4), d_NiN = 2.062(4), 2.087(4) Å, (II) d_CuO = 2.465(5), d_CuN = 1.994(5), 2.006(5) Å, (III) d_CuO = 2.464(5), d_CuN = 1.990(5), 2.036(5) Å. The neutral diol that results from hydrolysis of di-2-pyridyl ketone is stabilized by coordination to the metal and such coordination is little affected by changes in the metal, the anion or the extent of hydration.     

Chemistry of dithiocarbamate derivatives of amino acids. I. Study of some dithiocarbamate derivatives of linear α-amino acids and their nickel(II) complexes

The barium dithiocarbamate derivates of the α-amino acids glycine, DL-alanine, DL-2-amino- butyric acid, DL-norvaline and DL-norleucine have been synthesized. The crystal structure of the glycine derivative was determined. The anions were used to obtain the corresponding nickel(II) complexes in acid form. The complexes are diamagnetic, and coordination takes place in a near-square planar geometry around the Ni(II) ion through the sulphur atoms of the dithiocarbamate moiety, the structure having been confirmed by IR, ¹H NMR, UV-Vis spectroscopies and chemical analysis.     

Heteropolymetallic complexes of 1,1′-bis(diphenylphosphino)ferrocene (dppf). IV. Solvolytic behavior and cytostatic properties towards the KB cell-line of dppf and 1,2-bis(diphenylphosphino)ethane cis-complexes of Pt(II) and Pd(II)

The novel cis-platinum(II) complexes [(dppe)Pt(μ-OH)]₂(BF₄)₂ and [(dppe)Pt(DMF)₂](BF₄)₂ have been prepared and characterized by ³¹P NMR, together with cis-[(dppe)Pt(μ-Cl)]₂(BF₄)₂, both in poorly and strongly coordinating solvents (dppe = 1,2-bis(diphenylphosphino)ethane). All these complexes and their dppf analogs (dppf = 1,1′-bis(diphenylphosphino)ferrocene) as well as (dppf)PtCl₂, (dppe)PtCl₂, (dppf)PdCl₂, [(dppf)Pd(μ-Cl)]₂(BF₄)₂ and [(dppf)Pd(μ-OH)]₂(BF₄)₂ have been tested as antiproliferating agents towards Eagle's KB cell-line. Their activity is compared with that of free diphosphine ligands. For Pt(II) complexes, the ID₅₀ figures are found to be higher than those observed for free dppf and dppe. On the contrary, the activity of the palladium dppf complexes is substantially identical to that of free diphosphine.