Synthesis,characterization and antimicrobial activity studies of N - N ′-tetracarboxydiethyloxamide ligand and its metal(II) complexes

N-N′-tetracarboxydiethyloxamide (hereafter abbreviated as H₆L) was prepared by using L-aspartic acid and diethyl oxalate (DEO). A series of binuclear complexes of divalent metal chlorides viz. Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) with H₆L have been prepared. Spectral studies (IR, UV and NMR) magnetic susceptibility, elemental analysis and molar conductance measurements confirm the formation of binuclear complexes, [M₂H₂L]/[M₂H₂L?·?4H₂O]. Electronic absorption spectra and magnetic susceptibilities suggest square-planar stereochemistry for Cu(II) and tetrahedral for Zn(II) complexes. Mn(II), Co(II), and Ni(II) coordinate two molecules of water and consequently show octahedral geometry. The in vitro antimicrobial activity of the synthesized compounds is discussed against bacterial strains such as S. aureus, S. epididermis, K. pneumonia, S. typhi, P. aerugenosa, and B. subtilis A. brasilense. The metal complexes show higher activity against all the microorganisms than the ligand.     

Synthesis,characterization, and biological activity studies of copper(II)–metal(II) binuclear complexes of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazone)

A new series of copper(II) mononuclear and copper(II)–metal(II) binuclear complexes [(H₂L)Cu] ? H₂O, [CuLM] ? nH₂O, and [Cu(H₂L)M(OAc)₂] ? nH₂O, n = 1–2, M = Co(II), Ni(II), Cu(II), or Zn(II), and L is the anion of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazone), H₄L, were synthesized and characterized. Elemental analyses, molar conductivities, and FT-IR spectra support the formulation of these complexes. IR data suggest that H₄L is dibasic tetradentate in [(H₂L)Cu] ? H₂O and [Cu(H₂L)M(OAc)₂] ? nH₂O but tetrabasic hexadentate in [CuLM] ? nH₂O (n = 1–2). Thermal studies indicate that waters are of crystallization and the complexes are thermally stable to 347–402°C depending upon the nature of the complex. Magnetic moment values indicate magnetic exchange interaction between Cu(II) and M(II) centers in binuclear complexes. The electronic spectral data show that d–d transitions of CuN₂O₂ in the mononuclear complex are blue shifted in binuclear complexes in the sequences: Cu–Cu > Cu–Ni > Cu–Co > Cu–Zn, suggesting that the binuclear complexes [CuLM] ? nH₂O are more planar than the mononuclear complex. The structures of complexes were optimized through molecular mechanics applying MM ⁺force field coupled with molecular dynamics simulation. [(H₂L)Cu] ? nH₂O, [CuLM] ? nH₂O, and the free ligand were screened for antimicrobial activities on some Gram-positive and Gram-negative bacterial species. The free ligand is inactive against all studied bacteria. The screening data showed that [CuLCu] ? H₂O > [(H₂L)Cu] ? H₂O > [CuLZn] ? H₂O > [CuLNi] ? 2H₂O ≈ [CuLCo] ? H₂O in order of biological activity. The data are discussed in terms of their compositions and structures.     

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,structure, spectroscopic,magnetic and electrochemical studies of a rare syn–anti acetate-bridged copper(II) complex

The structure, spectroscopy and electrochemical properties of a novel dinuclear copper(II) complex, [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ where phen = 1,10-phenanthroline, is reported. The crystal structure contains two independent Cu(II) ions, with different geometry around each copper center, which are bridged by an acetate anion. The acetate-bridged ligand shows a syn–anti coordination mode with a trigonal bipyramidal geometry for the Cu(1) center and a distorted square-based pyramidal geometry for the Cu(2) center. The angular structural index parameter τ for Cu(1) and Cu(2) is 0.9 and 0.33, respectively. The copper(II) atoms display a different geometry with a N₄O chromophore group and with Cu–O distances of 1.993(5)–1.996(5) Å and Cu–N distances which vary from 1.980(5) to 2.161(6) Å. The intra Cu…Cu separation is 4.9904(5) Å. The effective magnetic moment (μ_eff) of the complex was measured by the Evans method. The cyclic voltammogram of [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ shows two waves at positive potential which are assigned to the two Cu(II/I) reduction couples.     

p-Tolylimido rhenium(V) complexes – Synthesis,X-ray studies,spectroscopic characterization and DFT calculations

The p-tolylimido rhenium(V) complexes [Re(p-NC₆H₄CH₃)X₃(EPh₃)₂] (X = Cl, Br; E = As, P) and [Re(p-NC₆H₄CH₃)Cl₂(hmpbta)(PPh₃)]·MeCN have been synthesized and characterized spectroscopically and structurally. The electronic spectra of [Re(p-NC₆H₄CH₃)Cl₃(PPh₃)₂] and [Re(p-NC₆H₄CH₃)Cl₂(hmpbta)(PPh₃)](Hhmpbta-2-(2′-hydroxy-5′-methylphenyl)benzotriazole) were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ. Additional information about bonding between the rhenium atom and p-tolylimido ligand in the complexes [Re(p-NC₆H₄CH₃)Cl₃(PPh₃)₂] and [Re(p-NC₆H₄CH₃)Cl₂(hmpbta)(PPh₃)] was obtained by NBO analysis.     

Synthesis,spectroscopic characterization,thermal stability and biological studies of mixed ligand complexes of gemifloxacin drug and 2,2′-bipyridine with some transition metals

Research on Chemical Intermediates - The mixed ligand Zn(II), Zr(IV), Pd(II), Ce(IV), Th(IV), and U(VI) complexes of gemifloxacin and N-donor 2,2′-bipyridine have been prepared. These...     

Synthesis,structure, and magnetic property of Co(II)-based metal–organic framework with 4,4′-oxy bis(benzoate) ligand

A 2-D coordination polymer, [Co(OBA)₂]_∞ (OBA?=?4,4′-oxy bis(benzoate)), where OBA ligands bridge cobalt in a terminal fashion to build up a 2-D layer structure with strong hydrogen-bonding interaction was isolated and structurally characterized from the reaction of OBA with Co(OAc)₂?·?4H₂O. Magnetic data indicate the Co(II) centers in 1 are negligibly magnetically coupled to each other and the single-ion magnetic behavior of Co(II) in octahedral environment is dominated at low temperature to give an effective S?′?=?1/2 ground state from S?=?3/2 state due to spin–orbit coupling.     

Synthesis,characterization, and DNA interaction of mononuclear copper(II) and zinc(II) complexes having a hard–soft NS donor ligand

Knoevenagel condensate-based Schiff base ligands (L) containing N and S donor sites have been designed and synthesized [L = 3-cinnamalideneacetylacetonethiosemicarbazone (CAT)/3-cinnamalideneacetylacetoneethylthiosemicarbazone (CAET)/3-cinnamalideneacetylacetonephenylthiosemicarbazone (CAPT)]. They afford complexes of the type [ML] [M = Cu(II) and Zn(II)]. Both the ligands and their complexes were characterized by analytical and spectral data. Intercalative binding of these complexes with DNA has been investigated by electronic absorption spectroscopy, viscosity measurements, cyclic voltammetry, and differential pulse voltammetry. Electrophoretic study of the complexes indicates that they efficiently cleave supercoiled pUC19 DNA in the presence of hydrogen peroxide.     

Synthesis,X-ray crystal structure,DFT calculations,spectroscopic characterization and redox behaviour of a rhodium(III) complex of an anthracene–pyridylhydrazone ligand

Transition Metal Chemistry - A pyridylhydrazone incorporating an anthracene moiety, designated as HLAnc, has been synthesized in order to examine its coordination behaviour towards rhodium(III)....     

Synthesis,structure and magnetic studies of copper(II)-nickel(II) complexes withN,N′-bis(2-aminopropyl)oxamidocopper(II)

Three novel heterobinuclear complexes have been prepared and identified as [Cu(oxap)Ni(L)₂](ClO₄)₂·ξH₂O, where oxap denotes theN,N′-bis(2-aminopropyl)oxamido dianion and L denotes 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) or 5-nitro-1,10-phenanthroline (NO₂-phen). The crystal structure of [Cu(oxap)Ni(phen)₂]-(ClO₄)₂·2H₂O has been determined. Crystal data: triclinic, space group , a=12.079 (6), b=12.409 (4), c=17.261 (8) ?, α=70.91 (2), β=86.72 (4), γ=89.19 (3)^o. At room temperature, Z=2. The Cu^II is in a square planar environment and the Ni^II is in an octahedral environment. The Cu−Ni distance is 5.292 ?. The temperature dependences of the magnetic susceptibilities of [Cu(oxap)Ni(phen)₂]-(ClO₄)₂·2H₂O and [Cu(oxap)Ni(bipy)₂](ClO₄)₂ have been studied in the 4.2–300 K range, giving the exchange integral J=−92.4 cm⁻¹ for bipy and J=−94.3 cm⁻¹ for phen. These results are commensurate with antiferromagnetic interactions between the adjacent metal ions.     

Novel dioxorhenium complex with bis(3,5-dimethypyrazol-1-yl)methane ligand – Synthesis,spectroscopic characterization,X-ray structure and DFT calculations

The reactions of [ReOBr₃(PPh₃)₂] and [ReOBr₃(AsPh₃)₂] with bis(3,5-dimethypyrazol-1-yl)methane (bdmpzm) have been examined and novel dioxorhenium(V) complex [ReO₂(bdmpzm)₂]Br · HBr · 2H₂O has been obtained. The compound has been studied by IR, UV–Vis, ¹H NMR spectroscopy, magnetization measurements and X-ray crystallography. The electronic structure of the [ReO₂(bdmpzm)₂]⁺ cation has been calculated with the density functional theory (DFT) method. The spin-allowed electronic transitions of [ReO₂(bdmpzm)₂]⁺ have been calculated with the TDDFT/PCM method, and the UV–Vis spectrum of [ReO₂(bdmpzm)₂]Br has been discussed on this basis.     

Structural,spectroscopic, and biological aspects of S∩N donor Schiff-base ligands and their chromium(III) complexes

New chromium(III) complexes are synthesized by classical thermal and microwave (MW)-irradiated techniques. The Schiff bases 2-acetylfuran-S-benzyldithiocarbazate (L¹H), 2-acetylthiophene-S-benzyldithiocarbazate (L²H), 2-acetylpyridine-S-benzyldithiocarbazate (L³H), and 2-acetylnaphthalene-S-benzyldithiocarbazate (L⁴H) were prepared by condensation of -S-benzyldithiocarbazate in ethanol with the respective ketones by using MW as well as conventional methods. The chromium(III) complexes have been prepared by mixing CrCl₃ · 6H₂O in 1 : 1 and 1 : 2 molar ratios with monofunctional bidentate ketimines. The structure of the ligands and their transition metal complexes were confirmed by elemental analysis, melting point determinations, molecular weight determinations, infrared (IR), electronic and electron paramagnetic resonance (EPR) spectral, and X-ray powder diffraction studies. On the basis of these studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode by S∩N donors. Thus, an octahedral environment around the chromium(III) has been proposed. The growth inhibiting potential of the ligands and complexes has been assessed against a variety of fungal and bacterial strains.     

Synthesis, characterization and cyclic voltammetric studies of β-ketooximato ruthenium(II) complexes

Summary -Ketooxime [RC(O)C(NOH)R] (R = Me or Ph) ligands (HL) react with [Ru(PPh₃)₃Cl₂] in refluxing EtOH to yield [Ru(PPh₃)₂(L)₂] complexes. For R = Me, one isomer was obtained, while two isomers were isolated when R = Ph, due to a bulk effect. The complexes are diamagnetic and absorb intensely in the vis. region due to MLCT transitions. In MeCN and CH₂Cl₂ solution, Ru^II-Ru^III oxidation occurs in the 0.69–0.92 V versus s.c.e. range. The oxidation potential depends on both the electronic nature of R and the stereochemistry of the complexes.     

Synthesis,spectroscopic, antimicrobial and anti-inflammatory studies of 5(2′-hydroxyphenyl)-3-(4-x-phenyl)pyrazolinates of copper(II) and their addition complexes with donor ligands

Complexes of copper(II) with 5(2′-hydroxyphenyl)-3-(4-x-phenyl)pyrazolines, (C₁₅H₁₂N₂OX)₂Cu [X =–H,–Cl,–CH₃,–OCH₃] have been synthesized with their addition complexes with 2,2′-bipyridine, 1,10-phenanthroline and triphenylphosphine. The complexes were characterized by elemental analyses, molecular weight measurement, magnetic, conductivity measurement, IR, electronic, ³¹P NMR, ESR and FAB mass spectra. The complexes were examined for crystalline/amorphous nature through XRD. Square-planar geometry around copper(II) is suggested with two bidentate pyrazoline ligands. In the additional complexes pyrazoline is monodentate. The bidentate and monodentate behavior of pyrazoline ligands was confirmed by IR and ³¹P NMR spectral data. All complexes were tested for in vitro antibacterial and antifungal activity and exhibit very good antibacterial and antifungal activity; coordination has a pronounced effect on the microbial activities. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties. All complexes and adducts displayed potent cytotoxic activity against Artemia salina. Anti-inflammatory activity was also carried out by the carrageenan induced rat paw edema test. The complexes and adducts were found to have higher anti-inflammatory activity.     

Crystal structure and spectroscopic properties of a new syn-anti carboxylate-bridged polymeric chain copper(II)–glycylglycine complex

A new polymer complex of copper(II)–glycylglycine?{[Cu(glygly)(H₂O)][Cu(glygly)(H₂O)₂]} _n ·5nH₂O (1) is reported. It crystallizes in the P2₁/c space group, with a?=?14.669(2), b?=?9.8480(10), c?=?14.053(2)?Å,?β?=?102.730(10)°?and Z?=?4. Compound 1 consists of [Cu(glygly)(H₂O)] _n 1D carboxylate-bridged polymeric chains, monomer Cu(glygly)(H₂O)₂ molecules which form hydrogen-bonded chains and uncoordinated water molecules. In all cases, the geometry around copper(II) is a slightly distorted square pyramid with the water oxygen at the apex of the pyramid. The ESR, UV-Vis and IR spectroscopy of the compound were also studied.     

Magnetic,spectroscopic and biological properties of copper(II) complexes of the tridentate ligand, α-N-methyl-S-methyl-β-N-(2-pyridyl)methylenedithiocarbazate(NNS) and the X-ray crystal structure of the [Cu(NNS)I2] complex

Copper(II) complexes of general formula, Cu(NNS)X ₂ · nH₂O (NNS = the 2-formylpyridine Schiff base of N-methyl-S-methyldithiocarbazate; X = Cl^–, Br^–, I^–, NCS^–; n = 0, 2) have been synthesized and characterized by elemental analysis and by magnetic and spectroscopic techniques. Based on magnetic and spectroscopic data, a monomeric five-coordinate square-pyramidal structure is assigned to these complexes. The crystal and molecular structure of [Cu(NNS)I₂] has been determined by X-ray diffraction. The complex has a monomeric square-pyramidal structure with the ligand coordinated to the copper(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thione sulfur atom. The fourth and fifth coordination sites are occupied by the iodide ligands. Antimicrobial tests indicate that Schiff base is inactive against the bacteria, Bacillus subtilis (mutant defective DNA repair), Pseudomonas aeruginosa, methicillin resistant Staphylococcus aureus and Bacillus subtilis (wild type) and weakly active against the fungi, Candida albicans, Candida lypolytica, Saccharomyces cereviseae and Aspergillus ochraceous but its copper(II) complexes, Cu(NNS)X ₂ are strongly active against these organisms. A cytotoxicity study of the compounds against leukemic and cervical cancer cells showed that the Schiff base is inactive, but the complexes, [Cu(NNS)I₂] and [Cu(NNS)(NCS)₂] · 2H₂O exhibit significant activity against cervical cancer cells with CD₅₀ values of 4.8 and 4.2 g, respectively.     

Synthesis and spectral studies of Cu(II), Ni(II), Co(II) macrocyclic complexes by template reaction of (±)- trans -1,2-diaminocyclohexane,metal(II) nitrate and salicylaldehyde derivatives

Six new macrocyclic complexes were synthesized by template reactions of salicylaldehyde derivatives with (±)-trans-1,2-diaminocyclohexane and metal(II) nitrates. The metal to ligand ratio was 1 : 1. The Cu(II) complexes are proposed to be square planar and the Ni(II) and Co(II) complexes are proposed to be tetrahedral. The complexes are 1 : 2 electrolytes as shown by their molar conductivities (Λ_M) in DMF. The metal complexes are characterized by elemental analyses, FT-IR, UV–Vis, magnetic susceptibility measurements, molar conductivity measurements and mass spectra.