Syntheses,characterization, X-ray crystal structures and emission properties of copper(II), zinc(II) and cadmium(II) complexes of pyridyl–pyrazole derived Schiff base ligand – Metal selective ligand binding modes

The varying coordination modes of the title ligand, L [5-methyl-1-(pyridin-2-yl)-N′-[pyridin-2-ylmethylidene]pyrazole-3-carbohydrazide] towards the different metal centers is reported by preparation and characterization of Cu(II), Zn(II) and Cd(II) complexes, [Cu(L)NO₃.H₂O](NO₃) (1) [Zn(L)₂](ClO₄)₂·2DMF (2) and [Cd(L)(I)₂] (3) respectively. In 1, the neutral ligand serves as tetradentate 4 N donor where both pyridine and pyrazole nitrogen atoms of pyridyl–pyrazole part are coordinatively active, leaving the carbonyl oxygen of the carbohydrazide part inactive. The same pyridine and pyrazole N atoms remain abstained from the coordination process towards the Zn(II) and Cd(II) metal centers. For 2 and 3 the ligand behaves as a tridentate NNO donor where the two nitrogen atoms come from azomethine, pyridine of pyridine-2-carbaldehyde parts and O from carbonyl oxygen atoms (carbohydrazide part). The complex 1 and 2 are distorted octahedral while complex 3 adopts distorted square pyramidal geometry. All the complexes are X-ray crystallographically characterized.     

Synthesis and structure of novel copper(II) complexes with pyrazole derived ligands and metal–ligand interaction in solution

Two new ligands of the coumarin type have been synthesized and characterized by ¹H, ¹³C NMR, IR and MS. The crystal and molecular structures of ligand 2, determined by the X-ray diffraction method, are presented. With copper(II) these ligands create solid complexes of the type CuLCl₂, where L is 5-(2-hydroxybenzoyl)-3-methyl-1-(2-pyridinyl)pyrazol-4-carboxylic acid methyl ester (2) or 3-methyl-1-(2-pyridinyl)-1H-chromene[4,3-c]pyrazol-4-on (3). The new copper(II) complexes have been characterized by elemental analysis and solid state FT-IR. The protonation constants of ligands 2 and 3 have been determined in 5% v/v 1,4-dioxane–water solution (25 °C). The coordination modes in the complexes with copper(II) are discussed for 2 on the basis of potentiometric and UV–Vis data.     

Synthesis,characterization and oxidase catalytic activity of vanadium(IV) and oxovanadium(IV) complexes with Schiff base ligands derived from β-diketones

New complexes of vanadium(IV) and oxovanadium(IV) with Schiff base ligands derived from -diketones and ethanolamine or o-aminophenol have been prepared and characterized by elemental analyses, electrical conductance, magnetic moment measurements, and by i.r., u.v.–vis. and e.p.r. spectroscopy. A distorted octahedral environment was proposed for the vanadium(IV) and oxovanadium(IV) complexes. The spectroscopic results were utilized to compute the important ligand field parameters. Three adduct complexes were isolated owing to the interaction of one oxovanadium complex with Lewis-bases in MeOH. Vanadium(IV) complexes exhibit promising catalytic activity towards the aerobic oxidation of p-phenylenediamine (PPD) to the corresponding semi-oxidized form (PPD⁺). A linear correlation exists between the oxidase catalytic activity and the Lewis acidity of the central vanadium(IV) ion created by the donating properties of the parent ligand.     

Synthesis,characterization and biological activity of copper(II) complexes with ligands derived from β-amino acids

Transition Metal Chemistry - Two copper(II) complexes with ligands derived from β-amino acids, 2-(1-aminocyclohexyl)acetic acid L1 and 2-(1-amino-4-(tert-butyl)cyclohexyl)acetic acid L2, were...     

Synthesis and characterization of a tetranuclear copper(Ⅱ) complex with a chiral Schiff base ligand

The title complex l-[Cu^Ⅱ₄（Hvap）₂（vap）₂（MeOH）₂]（CIO₄）₂ 1 has been synthesized and characterized by EA. IR,TGA,solid-state CD spectra and X-ray single-crystal analyses（l-H₂vap’.a Schiff base ligand derived from the condensation of o-vanillin and l-2-amino-3-phenyl-l-propanol）.Complex 1 crystallizes in monoclinic system,chiral space group P2₁ with a =10.4257（18）.b = 21.695（4）,c = 15.721（3）A,β= 94.443（3）.V= 3545.1（11） ³,Z=2,Cu₄C₇₀H₇₈N₄O₂₂Cl₂.Mr= 1652.42,D_c= 1.548 g/cm³, F（000）= 1704 andμ（MoKα） = 1.338 mm^-1.The final R = 0.0682 and wR = 0.1420 for 6170 observed reflections with I > 2σ（I） and R = 0.1775 and wR = 0.1830 for all data.The structure of complex 1 contains a boat-shaped(Cu₄O₄} motif.The solid-state CD spectra confirm the chiral nature of complex 1.     

Synthesis and characterization of new D-π-D type Schiff base ligands and its complexes with Cobalt(II), Ruthenium(II)

A Schiff base ligands, N-{(1E,2E)-3-[4-(dimethylamino)phenyl]prop-2-en-1-ylidene}-1,10-phenanthrolin-5-amine(mpa) and (1E,2E)-3-[4-(dimethylamino)phenyl]acrylaldehyde9H-fluoren-9-ylidenehydrazone(mfh), have been synthesized from the reaction of 4,5-diazafluorenone-9-hydrazone and 5-amino-1,10-phenanthroline with 4-(dimethylamino)cinnamaldehyde. The Co(II) and Ru(II) complexes of the ligands were prepared and characterized. The metal-to-ligand ratio of the Co(II) complex was found to be 2: 1 and that of the Ru(II) complex was found to be 1: 1. The ligands and complexes have been characterized by FTIR, UV-visible, ¹H NMR and fluorescence spectra, as well as, elemental analyses, TGA-DSC-DTG and mass spectra.     

Metal complexes derived from hydrazoneoxime ligands: III – Synthesis,characterization and electrospray ionization mass spectra of some nickel(II) complexes with aroylhydrazoneoximes

Five binuclear nickel(II) complexes [{Ni(L-R)}₂] derived from diacetylmonooxime aroylhydrazones (H₂L-R) have been prepared and characterized. In these complexes the oximate group functions as a bridge between the two nickel(II) ions. The corresponding octahedral bisligand complexes [Ni(HL-R)₂] have been also prepared and characterized. Reaction of [{Ni(L-R)}₂] with excess pyrazole (HPyr) afforded square planar [Ni(L-R)HPyr] complexes. The structure of [Ni(L-H)HPyr] (11), [Ni(L-CH₃O)HPyr] (13) and [Ni(L-Cl)HPyr] (14) have been determined by single-crystal X-ray diffraction. In these complexes, the Ni(II) is coordinated to the oximate nitrogen, hydrazone nitrogen and enolimine oxygen of the aroylhydrazoneoxime ligand, the fourth coordination site is occupied by pyrazole nitrogen. In 11 and 13 the molecular units are linked together by intramolecular NH?O hydrogen bonds forming a helical chain propagating along a and b axis respectively. The helical structure is stabilized by CH?O, CH?π and π?π noncovalent interactions. The structure of 14 consists of two independently crystallographic molecular units. The Ni1 molecular units are assembled together by CH?O and CH?Cl1 interactions forming a two dimensional sheet, while the Ni2 units are jointed together by CH?O and CH?C interactions forming a chain extending along b-axis which are enclosed between sheets of Ni1 units.     

Synthesis,characterization, crystal structure,and DNA binding of two copper(II)–hydrazone complexes

Two new Cu(II)–hydrazone complexes, [Cu(L)(Hbpe)ClO₄]·ClO₄·[Cu(L)Cl] (1) and [Cu(HL)₂]·1.5ClO₄·0.5OH (2) (where HL?=?(E)-N′-(1-(pyridine-2-yl)ethylidene)benzohydrazide and bpe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene), have been synthesized and characterized by physicochemical methods. The structures of the complexes have been established by single-crystal X-ray diffraction direct methods, which reveal that the metal ions have distorted square-pyramidal and square-planar geometries in 1, and a distorted octahedral geometry in 2. DNA binding of HL, 1, and 2, performed by UV–vis titration in tris-buffer medium, yielded binding constants, which are 9.5 × 10³, 1.88 × 10⁴, and 4.66 × 10⁴ M^?1, respectively. Viscosity measurements suggest a surface or groove-binding mode of interaction between CT-DNA with HL, 1, and 2.     

Synthesis and structural characterization of copper(II) complexes with the 2′-[1-(2-pyridinyl)ethylidene]oxalohydrazide ligand

The octahedral copper(II) complex with two 2-[1-(2-pyridinyl)ethylidene]oxalohydrazide molecules was synthesized from bis(acetylacetonato)copper(II) and 2-[1-(2-pyridinyl)ethylidene]oxamohydrazide (Hapsox). The complex is unstable when not in solution. X-ray analysis confirmed the tridentate coordination of the ligands in the monoanionic form. In addition, the stable tetrahedral copper(II) complex with one ligand molecule coordinated as a tridentate in the dianionic form was prepared by direct synthesis from Cu(NO₃)₂·3H₂O and Hapsox, and characterized by elemental analysis, magnetic measurements and by i.r. and u.v./vis. spectrophotometry.     

Metal complexes of a novel bis-β-diketone-type ligand and its copper(II) complexes of two-photon biological imaging

A curcumin derivative ligand,1,7-bis(3-methoxyl-4-acetoxyl)phenyl-1,6-heptadiene-3,5-diketone (diacetylcurcumin,abbreviated as HL),and its Cu and Ni complexes have been synthesized and fully characterized by elemental analyses,IR,1 HNMR and molar conductivity.The resulting complexes exhibit two-photon excited fluorescence (TPEF) in DMF,and have been proven to be potentially useful for two-photon microscopy imaging in living cells.In addition,cytotoxicity tests showed that the low-micromolar concentrations of ML 2 did not cause significant reduction in cell viability over a period of at least 24 h and should be safe for further biological studies.     

Synthesis and spectral characterization of sparteine and α -isosparteine complexes with copper(II) sulfate

Complexes of CuSO₄ of the general formula [Cu(C₁₅H₂₆N₂)SO₄] where [C₁₅H₂₆N₂] is sparteine or α-isosparteine have been obtained from copper(II) and an appropriate alkaloid. The 1?:?1 (metal?:?alkaloid) stoichiometry was confirmed by elemental analysis. The compounds have been characterized by mass spectrometry, IR, and UV–Vis spectroscopy. The magnetic properties were also determined; no anti-ferromagnetic behavior was observed. Information on the geometry of newly obtained compounds was obtained using quantum-chemical calculations.     

Synthesis and characterization of inclusion complexes of aliphatic-aromatic poly(Schiff base)s with β-cyclodextrin (highlight)

This paper describes the formation of polymer inclusion complexes(polymer-CD-ICs) between β-cyclodextrin(β-CD) and aliphatic-aromatic poly(Schiff base)s. Fourier transform infrared(FTIR) spectroscopy, ¹H nuclear magnetic resonance spectroscopy(¹H-NMR), thermogravimetric analysis(TGA) and X-ray diffraction(XRD) have been used to observe the formation of polymer-CD-ICs. In FTIR spectra, the characteristic peaks of β-CD at 3391 cm⁻¹ shifted to 3418 cm⁻¹ and the intense peak at 1602 cm⁻¹ due to the –C = N– stretching vibration diminished after formation of inclusion complexes. Compared the ¹H-NMR of polymer-CD-ICs with β-CD, the chemical shift of the protons H-3, H-5 have shifted to higher field after the formation of inclusion complexes, which is perhaps due to the interaction of these protons with polymers. The TGA analysis revealed that the polymer-CD-ICs had better thermal stability than β-CD, suggesting that the polymer increased the stability of β-CD. The X-ray diffraction patterns displayed that the strong peak for both polymer-CD-ICs at approximately 20.0° (2θ) may confirm their IC formation.     

Synthesis, structure and characterization of binuclear copper(Ⅱ) complexes

At room temperature, dibenzoyl peroxide undergoes oxidative addition reaction with metallic copper powder and pyridine N-oxide (triphenylphosphine oxide or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin) which affords the last products as binuclear copper(II) complexes, [Cu(C5H5NO)-(C6H5COO)2]2(1), [Cu(OPPh3)(C6H5COO)2]2(2) and [Cu(C6H5COO)(C26H2oN2)](3, C26H2oN2 is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin). The structure of the complexes were characterized by elemental analyses, IR spectra, TG-DTA and magnetic property. Crystals(1) are triclinic, space group P1,a=0.92617(36),b=1.06973(17), c=1.08813(29) nm, a=59.60(2)°, β=74.83(3)°,γ=72.80(2)°, V=0.880 nm3, Dc=1.520 g/cm3, Z=1, R=0.044, Rw=0.048, Mr=805.78, 3477 reflections with I > 3σ(I). Each copper(Ⅱ) ion is coordinated by two bridging bidentate benzoate ligands and one pyridine N-oxide or triphenylphosphine oxide to form dimeric binuclear molecules. The structure of the compound(1) shows a clear centre of symmetry.     

Synthesis and X-ray structure of platinum(II), palladium(II) and copper(II) complexes with pyridine–pyrazole ligands: Influence of ligands’ structure on cytotoxic activity

The new pyrazole ligand 5-(2-hydroxyphenyl)-3-methyl-1-(2-pyridylo)-1H-pyrazole-4-phosphonic acid dimethyl ester (2a) has been used to obtain a series of platinum(II), palladium(II) and copper(II) complexes (3a–7a) as potential anticancer compounds. The molecular structures of the platinum(II) and copper(II) complexes 3a and 6a have been determined by X-ray crystallography. The cytotoxicity of the phosphonic ligand 2a and its carboxylic analog 2b as well as their complexes has been evaluated on leukemia and melanoma cell lines. Copper(II) complexes were found to be more efficient in the induction of melanoma cell death than the platinum(II) or palladium(II) complexes. Cytotoxic effectiveness of compound 7b against melanoma WM-115 cells was two times better than that of cisplatin. The reaction of compound 5b with 9-methylguanine has been studied.     

Ruthenium(II)/(III) and oxovanadium(IV) complexes of highly conjugated β-diketones and their macrocyclic Schiff base binuclear copper(II) complexes

Ruthenium(II) complexes of the general formula [Ru(PPh3)2(L)(L)]ClO4 [L=2,2-bipyridine or 1,10-phenanthroline;L=2-hydroxy--4-X-phenylcinnamoylacetophenone] have been prepared by reacting L and L with Ru(PPh3)3Cl2 in CH2Cl2. The complexes are diamagnetic and absorb intensely in the visible region, owing to the MLCT transition. Hexacoordinated ruthenium(III) complexes, [RuCl2(PPh3)2(L)], have also been prepared by reacting Ru(PPh3)3Cl3 with -diketones. Solutions of ruthenium(III) complexes show rhombic e.s.r. spectra at 77 K, and distortion from the octahedral symmetry has been identified from the line spacings. The conjugation in diketones favours reversibility in RuII/III and RuIII/IV and stabilize ruthenium in different oxidation states owing to d–* interaction. Oxovanadyl(IV) complexes of the -diketones with a metal-to-ligand ratio of 1:2 and square pyramidal geometry were also prepared. The e.s.r spectra of these complexes show the presence of an unpaired electron in the dxy orbital and the hyperfine splitting constants are sensitive to solvent change. ¶ A new class of highly conjugated Schiff bases obtained from the above diketones and 2-aminothiophenol behave as dibasic, tridentate ligands in their copper(II) complexes. The subnormal magnetic moments and hyperfine splittings of these complexes are ascribed to an antiferromagnetic exchange interaction arising from dimerization. Cyclic voltammograms show that the electron transfer occurs in two steps corresponding to CuII–CuI and CuI–CuI redox states.     

Synthesis,characterization, and X-ray crystal structure analysis of Cd(ΙΙ) and Cu(II) complexes of an acyclic pentadentate Schiff base

Cd(ΙΙ) and Cu(II) complexes of an acyclic pentadentate Schiff base were prepared by template condensation of two equivalents of 2-acetylpyridine with one equivalent of bis(3-aminopropyl)amine in methanol. The resulting complexes [CdL(NO₃)]ClO₄ (1) and [CuL](ClO₄)₂ · CH₃CN (2) were characterized by X-ray crystallography, elemental analysis, IR and mass spectrometry in both cases and by NMR in the case of 1. The X-ray crystallographic structure determination of these complexes revealed six-coordinate distorted octahedral geometry for 1, with the sixth coordination by nitrate and five-coordinate for 2 with trigonal-bipyramidal Cu(II).     

Synthesis,characterization and medical efficacy (hepatoprotective and antioxidative) of albendazole-based copper(II) complexes – an experimental and theoretical approach

A series of albendazole-based copper(II) complexes with different counter anions, [Cu(Albz)(H₂O)₂](ClO₄)₂ (1), [Cu(Albz)₂(Cl)]Cl·2H₂O (2), [Cu(Albz)₂(NO₃)](NO₃) (3), and [Cu₂(Albz)₂(μ-SO₄)₂(H₂O)₂] (4) (Albz = albendazole), have been synthesized and characterized. Their structures and properties were characterized by elemental analysis, thermal analysis (TGA, DTG and DTA), IR, UV–vis and ESR spectroscopies, cyclic voltammetry, electrical molar conductivity, and magnetic moment measurements. A square-planar geometry is proposed for 1, whereas the five-coordinate copper(II) complexes 2, 3, and 4 have a square pyramidal geometry. Theoretical calculations (DFT) using B3LYP/6–311 + G(d,p) level of theory corroborated the experimental results to investigate both the drug Albz and its copper(II) complex, 1. The hepatoprotective and antioxidative efficacy of Albz and 1–4 were evaluated against carbon tetrachloride-induced acute hepatotoxicity in rats. Hepatotoxicity in experimental rats was evidenced by significant decrease in the antioxidant enzyme activities (SOD, GSH-S-transfers, and GSH-Rd levels). The results have strong impact for designing anticancer drugs, combined with their potential cytotoxic and antioxidant activities, which can be targeted selectively against cancer cells and increase their therapeutic index and advantages over other anticancer drugs. The DNA cleavage studies of Albz and its copper(II) complexes using genomic DNA indicated that Albz has no role in cleavage of DNA, and only 1 played a marked role in the DNA cleavage without any external additives.     

Solid–solid synthesis,characterization, thermal decomposition and antibacterial activities of zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base ligand

The zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base were synthesized by one-step solid–solid reaction at room temperature. The composition and structure of the complexes were characterized by elemental analyses, Fourier transform infrared spectra (FTIR), X-ray powder diffraction (XRD), and thermogravimetry and differential scanning calorimetry (TG–DSC). The crystal structure of the complexes belongs to monoclinic system with the lattice parameters: a = 0.6807 nm, b = 1.3818 nm, c = 1.2011 nm, β = 95.80° for [Zn(C₁₀H₉O₄N)(H₂O)₃], and a = 0.7457 nm, b = 1.3331 nm, c = 1.2560 nm, β = 91.89° for [Ni(C₁₀H₉O₄N)(H₂O)₃]·1.5H₂O. The experimental results indicate that the zinc and nickel ions are all six-coordinated by imino nitrogen, carboxylic oxygen, and phenolic oxygen from the Schiff base ligand, and oxygen from three coordinated water molecules, respectively. The possible pyrolysis reactions in the thermal decomposition processes of the complexes and the experimental and calculated percentage mass loss are also given. The two complexes have the most intense antibacterial activities against Escherichia coli.