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.     

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.     

Synthesis and antimicrobial activity of copper(II) and manganese(II) α,ω-dicarboxylate complexes

Copper(II) ,-dicarboxylate complexes of general formulae, [Cu(O₂C(CH₂)_nCO₂)]·xH₂O, [Cu(O₂C(CH₂)_nCO₂) (phen)₂]·xH₂O and [Cu(O₂C(CH₂)_nCO₂)(bipy)_y]·xH₂O (n=1–8; y=1, 2; phen = 1,10-phenanthroline; bipy = 2,2-bipyridine) were synthesised. These copper complexes, some related manganese(II) complexes and the metal-free ligands were screened in vitro for their ability to inhibit the growth of Candida albicans. Metal-free 1,10-phenanthroline and all of the copper(II) and manganese(II) phenanthroline complexes were potent growth inhibitors, with only one bipyridine complex, [Cu(O₂C(CH₂)CO₂)(bipy)₂]·2H₂O, having moderate activity. The remaining substances were effectively inactive. Complexes which were active against C. albicans also proved effective against C. glabrata, C. tropicalis and C. kreusi with the manganese complexes retaining superior activity. For the phenanthroline complexes the active drug species is thought to be the dication [M(phen)₂(H₂O)_n]²⁺ (M = Cu, Mn). Escherichia coli and Staphylococcus aureus were resistant to all of the metal complexes and also to metal-free 1,10-phenanthroline. Only the copper phenanthroline complexes showed intermediate activity against Pseudomonas aeruginosa.     

Synthesis and properties of (2-pyridyl)alkylamine- and (2-pyridyl)alkylamine–amide-coordinated copper(II) complexes: Structures and non-covalent interactions

Reaction of the ligand N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine (mpppa) with equimolar amounts of [Cu(H₂O)₆][ClO₄]₂ or CuCl₂ · 2H₂O in MeCN afforded mononuclear copper(II) complexes [Cu(mpppa)][ClO₄]₂ (1) and [Cu(mpppa)Cl₂] (2). Crystal structure analysis reveals CuN₃O (two pyridyl, an aliphatic amine, and an amide oxygen) coordination in 1 and CuN₃Cl₂ (two pyridyl, an aliphatic amine, and two chlorides) coordination in 2. Crystal packing diagram of 1 reveals that one of the perchlorate counteranions provides weak coordination to copper(II) centers and in turn the copper(II) centers assume pseudo-six-coordination, generating 1D chain. Notably, one of the copper(II)-coordinated chloride ions in 2 participates in an intramolecular N–H?Cl interaction. Intermolecular C–H?Cl interactions in the solid state generate helical structure. Spectroscopic (IR, UV–Vis, and EPR) and redox properties of the two complexes have been investigated and compared.     

Synthesis, crystal structure, magnetic properties and EPR spectra of copper(II) acetate derivatives: tetra-(μ-acetato)bis(2-methylaminopyridine)copper(II) and catena-poly(aquadiacetato-μ-3-aminomethylpyridine)copper(II). Sheets formed by chains connected through hydrogen-bonds

The derivatives of Cu(OAc)₂ · H₂O with 2-methylaminopyridine and 3-aminomethylpyridine, [Cu₂(μ-OAc)₄(MeNHpy)₂] (1) and [Cu(OAc)₂(μ-NH₂CH₂py)(H₂O)]_n (2), respectively, have been synthesized and characterized. Compound 1 shows the dimer structure of [Cu₂(μ-OAc)₄(H₂O)₂], with four syn-syn bridging acetate groups and the MeNHpy ligand coordinated in the axial positions. It is antiferromagnetic (2J=−285 cm⁻¹). Signals of the triplet state are observed in its EPR spectrum and the zero-field splitting parameter has been calculated (D=0.36 cm⁻¹; g_∥=2.35; g_⊥=2.07). Otherwise, the ligand 3-aminomethylpyridine acts as bridging bidentate ligand in compound 2, forming infinite zig-zag chains. Each copper atom lies in a square-planar pyramidal coordination, determined by two nitrogen atoms of two bridge ligands, two oxygen atoms of two monodentate terminal acetate groups and a water molecule. The parallel chains form a sheet because of the hydrogen bonds between them. The shortest Cu-Cu distances are: 5.1270, 6.0952 and 6.2163 Å (inter-chains) and 7.875 Å (intra-chain). Compound 2 shows a slight antiferromagnetic effect below 30 K. The EPR spectra show an orthorhombic signal (g₁=2.26; g₂=2.08; g₃=2.06).     

The coordination of copper(II) with β-casomorphin and its fragments

The synthesis of β-casomorphin-5 (Tyr-Pro-Phe-Pro-Gly, H₂L) and a number of its peptide fragments is described. Complexes formed between these peptides and Cu(II) have been investigated spectrophotometrically, using CD and EPR spectroscopy, and potentiometrically. Results show that, with tyrosine as the N-terminal residue, the major complex formed at physiological pH is the dimeric species, [Cu₂L₂], bonded through the phenolic O^? of the Tyr residue of one ligand and the N-terminal amine nitrogen of the second ligand molecule. There is no evidence for coordination through the peptide nitrogens unless the terminal Tyr group is removed.     

Structural and some medicinal characteristics of the copper(II)–hydroxychloroquine complex

In the first phase of this study, the binding of hydroxychloroquine to the copper(II) cation is examined using liquid chromatography–mass spectrometry (LC–MS), matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS), Fourier transform-ion cyclotron resonance spectrometry (FT-ICR) and nuclear magnetic resonance (¹H and ¹³C NMR) in one and two dimensions. The data suggest the metal–ligand complex is a polarity adaptive molecule. In the second phase of the study, the complexes activity is tested against the National Cancer Institute’s 60 cell line panel. Its anti-cancer activity is compared to quinine, Cu(II)–quinine and hydroxychloroquine. It serves as a base line for future anti-cancer complexes in which hydroxychloroquine is utilized for its ability to impact cell autophagy.     

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.     

A novel unsymmetrical quadridentate ligand 1-(2′-aminophenyl)-6-methyl-2,5-diazanona-l,6-diene-8-one and its complexes with copper(II), nickel(II) and palladium(II)

Two routes for the preparation of the title compound (6) have been developed. Reaction of equimolar quantities of 2-aminobenzaldehyde, pentane- 2,4-dione and 1,2-diaminoethane yields the ligand 6 and 2-methyl-3-acetylquinoline as side product. The compound 6 was obtained in high yield in a one- step condensation of 2-aminobenzaldehyde with 1-amino-4-methyl-3-azahept-4-ene-6-one (5). Studies on the condensation of 5 with various 2-aminobenz- aldehyde derivatives revealed that the yield of unsymmetrical ligand is evidently influenced by the acidic properties of the hydrogen atom (of atoms) of the ring substituent in the ortho position to the carbonyl group. Copper(II), nickel(II) and palladium(II) complexes of 6 have been prepared and characterized. Spectroscopic data of nickel and palladium complexes are consistent with their planar structure. A superhyperfine splitting due to nitrogen is observed in the EPR spectrum of the copper complex in spite of the presence of azomethine hydrogen atom.     

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.     

Detection of low molecular weight copper(II) and zinc(II) binding ligands in ultrafiltered milks—the citrate connection

Low molecular weight zinc(II) and copper(II) binding ligands were detected in ultrafiltered human, bovine, and goat milk by the application of the method of modified gel chromatography. Human milk contains at least three detectable low molecular weight copper binders, whereas bovine and goat milk contain at least two. All three milks show two copper binding peaks with the same elution volumes. Zinc chromatograms were less specific than copper. Zinc showed only a single detectable low molecular weight binding ligand common to all three milks. Elution volumes for both zinc(II) and copper(II) citrate and picolinate systems were measured. Elution volumes of both copper(II) and zinc(II) citrate complexes are identical to elution volumes of an intense peak observed with all three milks; it is reasonable to assume that at least part of this peak corresponds to citrate. Human milk alone has a relatively intense binding peak for copper(II) at the same elution volume as the glutamate complex. Human and goat milk have another low intensity copper(II) binding ligand peak at the same elution volume; a number of amino acid complexes have binding peaks at this position. No peak characteristic of the zinc(II) or copper(II) picolinate systems could be found with any of the milks.     

Electronic coupling and photochemical stability of O,N bound mononuclear Ru(II) and Os(II) – Hydroquinone complexes

The synthesis, spectroscopic and electrochemical characterisation of a series of optically tuneable, ruthenium (II) and osmium (II) polypyridyl complexes, O,N coordinated to electroactive donor ligand, bis-2,5-(2-benzoxazolyl)-hydroquinone (bbhq) is described. The complexes exhibit a rich optical spectroscopy which can be controlled through the redox state of the metal and bbhq ligand. The influence of both the metal and counter-ligand identity on the optical properties of these hydroquinone-based complexes is addressed.Regardless of the identity of metal or counter-ligand, it is the bbhq which is the site of the most facile oxidation and hydroquinone, semiquinone (bbsq) and quinone (bbq) can be generated electrochemically. In each instance, the semiquinone is strongly stabilised with respect to disproportionation, reflected in large stability constants for this moiety. The levels of orbital mixing between metal and ligand are discussed on the basis of the optical properties of the complex and the nature of the metal and counter-ligand. In addition, we address, for the first time, the effect of metal and counter-ligand on the photostability, of Ru(II) and Os(II) hydroquinone bound complexes. We find that like other ruthenium (II) complexes containing strong σ-bonding ligands, the M(bpy)₂ containing complexes are photostable, but the [Ru(biq)₂(bbhq)]⁺ complex is relatively photolabile.     

Relationship between copper biosorption and microbial inhibition of hydroxyl radical formation in a copper(II)–hydrogen peroxide system

The microbial retardation of the spin adduct, DMPO-OH, formed in a copper(II)–hydrogen peroxide–DMPO (5,5-dimethyl-1-pyrroline N-oxide) solution was examined in relation to copper biosorption. A hydroxyl radical is formed in the solution through two steps, the reduction of Cu(II) to Cu(I) by H₂O₂ and the Fenton-type reaction of Cu(I) with H₂O₂. The resultant radical is trapped by DMPO to form DMPO-OH. Microbial cells retarded the DMPO-OH in the Cu(II)–H₂O₂–DMPO far more significantly than in the UV-irradiated H₂O₂–DMPO solution. Egg albumin showed a higher DMPO-OH retardation than microbial cells both in the Cu(II)–H₂O₂–DMPO and the UV-irradiated H₂O₂–DMPO solutions. These results indicated that the retardation effect is related to organic matter and not to microbial activity. Microorganisms having higher affinities for copper ion retarded DMPO-OH more significantly. The linear relationship between the amounts of copper biosorption and the inverse of the median inhibitory doses for DMPO-OH indicated that the microbial cells inhibited the reduction of Cu(II) to Cu(I) by H₂O₂, followed by the decrease of hydroxyl radical formation and the retardation of DMPO-OH. These results also suggest that the coupling between microbial cells and Cu(II) ion can be estimated from their ability to retard DMPO-OH.     

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.     

Synthesis and spectroscopic studies of platinum(II) complexes of N,N′-dicyclohexylethylenediamine

The platinum(II) complexes of the formula [Pt(DCHEDA)X₂], where DCHEDA is N,N′-dicyclohexylethylenediamine and X⁻ is CL⁻, Br⁻, I⁻, 0.5C₂O₄²⁻ (oxalate), 0.5C₃H₂O₄²⁻ (malonate), 0.5C₉H₄O₆²⁻ (4-carboxyphthalate), 0.5S₂O₃²⁻ or 0.5SO₄²⁻, have been synthesized and characterized by UVVis, IR, and ¹H NMR spectral techniques. All the above complexes are non-electrolytes in DMF/H₂O, except the sulphate complex which becomes a 1:1 electrolyte after incubation for 24 h at 28 °C. The halide complexes were also studied by X-ray photoelectron spectroscopy and these data suggest that there is π-bonding from platinum to halide in these complexes. The oxalate, malonate and sulphate bind in their complexes as bidentate ligands to platinum through two oxygen atoms whereas the thiosulphate in its complex binds as a bidentate ligand to platinum through one oxygen atom and one sulphur atom.     

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.     

Structures and magnetic property studies of four copper(II) and nickel(II) supramolecular complexes derived from diphenic acid constructed by C-H?π and π-π interactions

Four one-dimensional metal-organic polymers derived from diphenic acid (H₂dpa) were synthesized in the presence of auxiliary ligands, [Cu(dpa)CH₃OH](1), [Ni(dpa)CH₃OH] (2), [Cu(bipy)₂(Hdpa)₂(H₂O)₂] (3) and [Ni(bipy)₂(Hdpa)₂(H₂O)₂] (4) (bipy = 4, 4′-bipyridine). The dinuclear paddle-wheel second building units (SBUs) constructed by four dpa²⁻ ligands in complexes 1 and 2 are linked by dpa²⁻ into double chains, which are connected by C-H?π interactions forming a two-dimensional rhombic porous structure. In complexes 3 and 4, the metal ions are connected by bipy ligands, and the grid-like network was formed with the π-π interactions between the adjacent phenyl rings of Hdpa⁻. For 1 and 2, there are strong antiferromagnetic interactions within Cu-Cu and Ni-Ni dimers. It is also strong antiferromagnetic interactions between the dimmers of Cu₂ in 1, while it is weaker of those of Ni₂ in 2. Weaker antiferromagnetic interactions exist among Cu-Cu and Ni-Ni in 3 and 4, in which bipy is the effective coupling media. Thermally gravimetric analyses and differential thermal analyses indicate that the four complexes are all thermal stable.