Synthesis, crystal structure and surface photo-electric property of a series of Co(II) coordination polymers and supramolecules

Four new Co(II) coordination complexes, [Co(o-phta)(pz)₂]_n1, [Co(PTA)₂(Imh)₂]·(HPTA)·H₂O 2, {[Co(pdc)₂(H₂O)]·(ppz)·2H₂O}_n3, [K₂Co₂(ox)(btec)(CH₃OH)₂]_n4, (H₂phta = o-phthalic acid, pz = pyrazole, HPTA = p-toluic acid, ppz = piperazine, Imh = imidazole, H₂pdc = pyridine-2,5-dicarboxylic acid, H₂(ox) = oxalic acid, H₄btec = 1,2,4,5-benzenetetracarboxylic acid), were hydrothermally synthesized and characterized by X-ray single crystal diffraction, IR, UV–Vis absorption spectrum, TG analysis and elemental analysis. The surface photovoltage properties of the four Co(II) complexes were investigated by the surface photovoltage spectroscopy (SPS). The structural analyses indicate that complexes 1 and 3 are 1D coordination polymers and complex 2 is a mononuclear molecular complex. Complexes 1, 2 and 3 are connected into 2D supramolecules by hydrogen bonds, respectively. Complex 4 is a coordination polymer with 3D structure, exhibiting a 4-nodal(4,5,6,12)-connected topology with a Schläfli symbol of (4¹⁰)₂(4²⁴·6³²·8¹⁰)(4⁵·6)₂(4⁹·6⁵·8). The results of SPS show the four complexes exhibit obvious photovoltaic responses in 300–800 nm, which indicates they all possess photo-electric conversion properties. By the comparative analysis of the SPS, it is found that structure of the complex, species of ligand and coordination micro-environment of the Co(II) ion affect the SPS. The relationships between SPS and UV–Vis absorption spectra are discussed.     

Synthesis,spectral characterisation and cytotoxic effect of metal complexes of 2-(2-(4-carboxyphenyl)guanidino) acetic acid ligand

Abstract

A new series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Sr(II), Hg(II), Ag(I), Tl(I) and UO₂(II) complexes of 2-(2-(4-carboxyphenyl)guanidino)acetic acid ligand have been synthesised and characterised by elemental analyses, IR, UV-Vis spectra, mass spectra (ligand and its zinc(II) complex), ¹H NMR spectra (ligand and its mercury(II) complex), magnetic moments, conductances, thermal analyses (DTA and TGA) and ESR measurements. The IR data show that, the ligand behaves as neutral tridentate, (2), [(H_{2 L}L)_{3 C}Cu_{2 (}(OAc)_{4 (}(H_{2 O}O)_{2 ]} ], neutral bidentate, (3), [(H_2LL)Cu(OAc)_2]].1/2H_2OO, (13), [(HL)_2CCuCl₂₍(H_2OO)_2]], (17), [(H_2LL)Cu(OOSO₂₎)(H_2OO)J,dibasic hexadentate, (4), [(L) Ni₄₍(OAc)₆₍(H_2OO)J.4H_2OO, (5), [(L)Mn4(OAc)6(H2O)10]. 4H2O, (6), [(L)Co4(OAc)6(H2O)10] . 4H2O, monobasic bidentate, (7), [(HL)(UO2)(OAc)(H2O)3], (12), [(HL)2Cu], (15), [(HL)2Fe2(Cl4)(H2O)2]. 7H2O, (16), [(HL)2Cr2(Cl4)(H2O)2]. 7H2O, (21 ), [(H2L)Cd (OOSO2)(H2O)3]. 2H2O, monobasic tridentate, (8), [(L)_2HHg₂₍(OAc)₂ (H2O)6].H2O, (9), [(L)2Zn2(OAc)2(H2O)6].H2O, (10), [(L) _2ZZn₂₍(OAc)₂₍(H_2OO)_6]].H_2OO, (11), [(L)Tl4(OAc)3 (H2O)6], (18), [(HL)(OH)Cr2(SO4)2(H2O)5]. H2O, (19), [(HL)3Ag3NO3], or dibasic tridentate, (14), [(L) Sr(Cl)_{20 (}(H_{2 O}O)_{24 ]}], (20), [(L)_{3 C}Cu (H_{2 O}O)_{2 ]} ]. Molar conductances in DMF indicate that, the complexes are non-electrolyte. The ESR spectra of Cu(II) complexes (2), (3) and (20) at room temperature show axial type symmetry with g_// > g_-> 2.00, indicating a d_(x2-y2) ground state with significant covalent bond character in an octahedral or square planar geometry. However, Cu(II) complexes (12) and (13) show isotropic type, indicating square planar and octahedral structure. Complexes Mn(II) (5) and Co(II) (6) show broad signals in the low field region indicating spin exchange interaction take place between metal(II) ion. Hg(II) complex (9), Tl(I) complex (11), Cr(III) complex (16), Cu(II) complex (17) and Cd(II) complex (21) showed potential antiproliferative activity where they showed inhibitory effect on breast carcinoma (MCF-7 cell line) in comparing with the standard drug.     

A Co-monosubstituted Keggin polyoxometalate with an antenna ligand and three cobalt(II) chains as counterion

A Co-monosubstituted Keggin polyoxometalate with an antenna ligand linked to the Co(II) center with a Co(II)-containing cation has been prepared. The title compound, formulated as {Co(H₂O)₄(4,4′-bpy)}₂(4,4′-Hbpy)₂[SiW₁₁Co(4,4′-bpy)O₃₉] · 5H₂O (1) (4,4′-bpy = 4,4′-bipyridine), was synthesized and characterized by elemental analysis, IR spectra, TG analysis, X-ray single crystal structure analysis and magnetic measurements. As far as we know, the title compound represents the first Co(II) substituted Keggin polyoxometalate with an antenna ligand structurally and magnetically characterized.     

Molecular Structure and Cytotoxicity of 3D-Transition Metal Complexes Capable to Form a Stable Metal-Nitrogen Bond

Abstract

The cytotoxicity of several Co(II), Ni(II), Cu(II) and Zn(II) complexes with various molecular structures and geometries, has been tested on LoVo and 2008 cells at 1–100 μM concentration for 24 h exposure. On the basis of 24 h results, the exposure time was prolonged to 48 and to 72 hours. The most potent complexes result [Cu(tren)(H₂O)]²⁺ 2Cl^?, E, [CoCl₃(H₂Meppz)], G, and [CoCl₃(HMe₂ppz)], H, (tren=tris(2-aminoethyl)amine, H₂Meppz=1-methylpiperazin-1-ium, HMe₂ppz=1,4-dimethylpiperazin-1-ium cations). Nevertheless, these complexes are able to induce cell growth reduction of about 50% at highest doses tested (1-100 μM) and after 72 h exposure.     

Transition-metal(II) thiocyanate coordination compounds containing 4-allyl-1,2,4-triazole. Structure and magnetic properties.

The synthesis and characterisation of a series of dinuclear and polynuclear coordination compounds with 4-allyl-1,2,4-triazole are described. Dinuclear compounds were obtained for Mn(II) and Fe(II) with composition [M₂(Altrz)₅(NCS)₄], and for Co(II) and Ni(II) with composition [M₂(Altrz)₄(H₂O)(NCS)₄](H₂O)₂. The crystal structure of [Co₂(Altrz)₄(H₂O)(NCS)₄](H₂O)₂ was solved at room temperature. It crystallizes in the monoclinic space group P2₁/n. The lattice constants are a = 18.033(3) Å, b = 13.611(2) Å, c = 15.619(3) Å, β = 92.04(2)° Z = 4. One cobalt ion has an octahedrally arranged donor set of ligands consisting of three vicinal nitrogens of 1,2-bridging triazoles (CoN = 2.14–2.15 Å), one terminal triazole nitrogen (CoN = 2.12 Å) and two N-bonded NCS anions (CON = 2.08 Å). The other Co(II) ion has the same geometry, but the terminal triazole ligand is replaced by H₂O (CoO = 2.15 Å). The crystal structure is stabilised by hydrogen bonding through H₂O molecules, S-atoms of the NCS anions and the lone-pair electron of the monodentate triazole. The magnetic exchange in the Mn, Co and Ni compounds is antiferromagnetic with J-values of ?0.4 cm^?1, ?10.9 cm^?1 and ?8.7 cm^?1 respectively. The Co compound was interpreted in terms of an Ising model. For [Zn₂(Altrz)₅(NCS)₂]∞[Zn(NCS)₄], [Cu₂(Altrz)₃(NCS)₄]∞ and [Cd₂(Altrz)₃(NCS)₄]∞ chain structures are proposed. In the Cu compound thiocyanates appear to be present, bridging via the nitrogen atom, as deduced from the IR spectrum.     

Syntheses, crystal structures and magnetic properties of 1D and 2D cobaltous coordination polymers with mixed ligands

Two new Co(II) coordination polymers with mixed ligands, {[Co(BTA)_0.5(DBI)₂]·DBI·H₂O}_n (1) and [Co(PDA)(DBI)(H₂O)]_n (2) (H₄BTA = benzene-1,2,4,5-tetracarboxylic acid; H₂PDA = 2,2′-(1,2-phenylene)diacetic acid; DBI = 5,6-dimethyl-1H-benzoimidazole) have been synthesized under hydrothermal conditions, respectively. Both of them are characterized by elemental analyses, powder X-ray diffraction, thermogravimetric analysis, single-crystal X-ray diffraction, and magnetic susceptibilities. In 1, the Co(II) ions are four-coordinated and lie in distorted tetrahedron coordination environment. 1D ladder-like chain structure is formed by the bridging BTA⁴⁻ ligand. In 2, the Co(II) ions are in slightly distorted octahedral coordination geometry, and linked by PDA²⁻ ligand exhibiting a 2D layer structure. Temperature-dependent magnetic susceptibility measurements of 1 and 2 revealed that there are antiferromagnetic interactions between Co(II) ions.     

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.     

Exploring the effect of chain length of bridging ligands in coordination complexes and polymers derived from mixed ligand systems of pyridylnicotinamides and dicarboxylates

The supramolecular structural diversities in mixed ligand systems derived from a series of dicarboxylate anions with varying chain lengths and N-donor exo-bidentate ligand equipped with hydrogen bonding capable amide backbone with Co(II)/Zn(II) metal centers are analyzed. In this context, two complexes namely (Co(L1)₂(malonate)(H₂O)₂} (1a), {Zn(L1)₂(malonate)(H₂O)₂} (1b) and one coordination polymer namely {[Co(μ-L1)(μ-glutarate)(H₂O)] · H₂O}_n (4) (where L1 = N-(4-pyridyl)nicotinamide) have been synthesized and crystallographically characterized. The main aim of this work is to explore the effects of chain lengths of the anionic carboxylate ligands such as malonate, succinate, maleate, and glutarate, in determining the final architecture of coordination compounds based on the mixed ligands. Analyses of the structures revealed that the length of the bridging ligands have prominent effect in the formation of hierarchical structures.     

Synthesis, crystal structure, hydrogen bonding and spectroscopy of Co, Mn and Ni oxalate complexes with the ligand (N,N′-bis(2-pyridylmethyl)-1,3-propanediamine)

Three new compounds are reported with the tetradentate ligand (N,N′-bis(2-Pyridylmethyl)-1,3-propanediamine) (abbreviated as pypn), two mononuclear compounds i.e. [Co(pypn)(C₂O₄)](ClO₄) (1), [Mn(pypn)(C₂O₄)](ClO₄) (2) and one dinuclear compound [Ni₂(pypn)₂(C₂O₄)](ClO₄)₂(C₂H₆O)_1/4(H₂O) (3). In the Co(III) and Mn(II) complexes the oxalate behaves as bidentate ligand, chelating the metal in the O,O′ mode, whereas in the Ni(II) compound the oxalate behaves as tetradentate ligand binding each Ni(II) ion by two oxygen atoms and bridging the two metallic centers.The synthesis, X-ray crystal structure of all three compounds and their spectroscopic properties are presented in detail. The geometry around the Co³⁺, Mn³⁺, Ni²⁺ ions is essentially octahedrally based, while the stabilization of the crystal lattice in all cases is maintained by interesting hydrogen bond systems.     

Supramolecular cobalt(II)-pyridine-2,5-dicarboxylate complexes with isonicotinamide, 2-amino-3-methylpyridine and 2-amino-6-methylpyridine: Syntheses, crystal structures, spectroscopic, thermal and antimicrobial activity studies

The mer-[Co(pydca)(H₂O)₃(ina)]·H₂O (1), (2a3mpyH)₂[Co(pydca)₂(H₂O)₂]·2H₂O (2) and (2a6mpyH)₂[Co(pydca)₂(H₂O)₂]·2H₂O (3) complexes (H₂pydca: pyridine-2,5-dicarboxylic acid, ina: isonicotinamide, 2a3mpy = 2-amino-3-methylpyridine and 2a6mpy = 2-amino-6-methylpyridine) were synthesised and characterised by elemental analysis, magnetic and spectroscopic measurements (UV-Vis and IR spectra) and single crystal X-ray diffraction technique. The thermal behaviour of the complexes was also studied by simultaneous thermal analysis techniques (TG, DTG and DTA). In complex 1, Co(II) ion was coordinated by one bidentate pydca, one isonicotinamide and three aqua ligands to generate a CoN₂O₄ distorted octahedral geometry. Complexes 2 and 3 crystallise in the triclinic system and space group and the structures consist of one complex anion [Co(pydca)₂(H₂O)₂]²⁻, two protonated aminomethylpyridinium cations, ampyH⁺ and two crystal water molecules. In the anions, the Co(II) ions have a distorted octahedral configuration and are coordinated by two bidentate pydca and two trans-aqua ligands. The pydca ligand is coordinated to the Co(II) by both the heterocyclic N atom and the adjacent carboxylate group O atom, creating a chelate ring, while protonated ampy ions behave as counter ion.     

Pyrazolato-bridged 1-D Co(II) coordination polymer and dinuclear Ni(II) and Cu(II) complexes: Syntheses, crystal structures and magnetic properties

Three complexes of composition [Co₃(Hdcp)₂(phen)₃(H₂O)₂]_n · nH₂O (1), [Ni₂(Hdcp)₂(H₂O)₄](Im)₂ (2) and [Cu₂(Hpca)₂(H₂O)₂(Im)₂] (3) (H₃dcp = 3,5-pyrazoledicarboxylic acid, H₂pca = 1H-pyrazole-5-carboxylic acid, Im = imidazole and phen = 1,10-phenanthroline) have been synthesized via hydrothermal reactions and their structures have been characterized. Complex 1 is mainly constructed by Hdcp and ancillary ligand 1,10-phenanthroline and exhibits one-dimensional linear chain structure. Complexes 2 and 3 are pyrazolato-bridged dinuclear complexes. The ancillary imidazole ligand was not involved in the coordination and stacked to the lattice of the complex in 2. In the process of synthesis 3, imidazole ligand was coordinated to the metal centre; with one of the carboxylic group of the H₃dcp ligand was eliminated to form [Cu₂(Hpca)₂(H₂O)₂(Im)₂] (3) in situ. The results of magnetic susceptibility measurements indicate that there exist antiferromagnetic interactions between Co(II) and Ni(II) centres in compounds 1 and 2, respectively.     

Synthesis, characterization and properties of series coordination polymers constructed from a biphenyl dicarboxylate and nitrogen-containing mixed ligands

A series of coordination polymers have been prepared by the combination of flexible ligand 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂dpa) and different types of nitrogen-containing ligands, with various metal ions such as Co(II), Zn(II) and Cd(II). The single-crystal structure analyses reveal that the above complexes possess different structure features with the introduction of different nitrogen-containing ligands. When auxiliary linear ligand 4,4′-bipyridine (4,4′-bpy) is introduced, two-dimensional layered complex, [Co₂(dpa)₂(4,4′-bpy)₂(H₂O)]_n (1) is formed. Whereas if chelating ligand, 1,10-phenanthroline (1,10′-phen) and 2,2′-bipyridine (2,2′-bpy) are introduced, one-dimensional complex [Zn(dpa)(1,10′-phen)]_n (2) and discrete complexes [Co₂(dpa)₂(2,2′-bpy)₂(H₂O)₂] (3), [Co₃(dpa)₃(1,10′-phen)₆(H₂O)₂] (4), [Cd(dpa)(1,10′-phen)₂][(H₂dpa)₂(H₂O)₂] (5) are synthesized. To our interest, 1 and 2 crystallize in homochiral spacegroup. Furthermore, the magnetic property of complex 1 and the fluorescent properties of complexes 2 and 5 are studied.     

Cobalt(II) complexes of the antibiotic sulfadiazine, the X-ray single crystal structure of [Co(C10H9N4O2S)2(CH3OH)2]

Cobalt(II) complexes of sulfadiazine formulated as [Co(C₁₀H₉N₄O₂S)₂(CH₃OH)₂] and [Co(C₁₀H₉N₄S)₂(H₂O)₂] have been synthesized and characterized by elemental analysis, infrared and UV-Vis spectroscopy and magnetic susceptibility measurements. The crystal structures of the complex [Co(C₁₀H₉N₄O₂S)₂(CH₃OH)₂] and of free sulfadiazine are also reported. The cobalt complex and the sulfadiazine ligand both crystallize in the monoclinic space group, P21/c, with sulfadiazine acting as a bidentate ligand. Cobalt is coordinated to two-sulfonamide nitrogen and the pyrimidine nitrogen of the sulfadiazine. Two molecules of methanol complete the octahedral geometry around the cobalt, with interligand hydrogen bonding between methanol and sulfadiazine. Infrared spectroscopy confirmed the presence of water molecule in the coordination sphere of [Co(C₁₀H₉N₄S)₂(H₂O)₂]. The electronic spectra and magnetic moments of both complexes were similar, indicating that both complexes have similar structure.     

Structure–activity relationship study of copper(II) complexes with 2-oxo-1,2-dihydroquinoline-3-carbaldehyde (4′-methylbenzoyl) hydrazone: synthesis, structures, DNA and protein interaction studies, antioxidative and cytotoxic activity

Novel 2-oxo-1,2-dihydroquinoline-3-carbaldehyde (4′-methylbenzoyl) hydrazone (H₂L) (1) and its two copper(II) complexes have been synthesized. Single-crystal X-ray diffraction studies revealed that the structure of the new copper(II) chloride complex, [Cu(H₂L)Cl₂]·2H₂O (2), is square pyramidal and that of the copper(II) nitrate complex, [Cu(HL)NO₃]·DMF (3), is square planar. In 2, the copper atom is coordinated by the ligand with ONO donor atoms, one chloride ion in the apical position, and the other chloride in the basal plane. In 3, the ligand coordinates as a uninegative tridentate ONO⁻ species and with one nitrate ion in the basal plane. DNA binding experiments indicated that the ligand and copper(II) complexes can interact with DNA through intercalation. Bovine serum albumin binding studies revealed that the compounds strongly quench the intrinsic fluorescence of bovine serum albumin through a static quenching process. Antioxidative activity tests showed that 1 and its copper(II) complexes have significant radical scavenging activity against free radicals. Cytotoxic activities of the ligand and copper(II) complexes showed that the two copper(II) complexes exhibited more effective cytotoxic activity against HeLa and HEp-2 cells than the corresponding ligand. The entire biological activity results showed that the activity order was 1 < 2 < 3.     

Anti-oxidant,in vitro,in vivo anti-inflammatory activity and antiproliferative activity of mefenamic acid and its metal complexes with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II)

Some new complexes of mefenamic acid with potentially interesting biological activity are described. The complexes of mefenamic acid [Mn(mef)₂(H₂O)₂], 1, [Co(mef)₂(H₂O)₂], 2, [Ni(mef)₂(H₂O)₂], 3, [Cu(mef)₂(H₂O)]₂, 4 and [Zn(mef)₂], 5, were prepared by the reaction of mefenamic acid, a potent anti-inflammatory drug with metal salts. Optical and infrared spectral data of these new complexes are reported. Monomeric six-coordinated species were isolated in the solid state for Mn(II), Ni(II) and Co(II), dimeric five-coordinated for Cu(II) and monomeric four-coordinated for Zn(II). In DMF or CHCl₃ solution the coordination number is retained and the coordinated molecules of water are replaced by solvent molecules. The anti-oxidant properties of the complexes were evaluated using the 1,1-diphenyl-2-picrylhydrazyl, DPPH, free radical scavenging assay. The scavenging activities of the complexes were measured and compared with those of the free drug and vitamin C. We have explored their ability to inhibit soybean lipoxygenase, β-glucuronidase and trypsin- induced proteolysis. The complex [Mn(mef)₂(H₂O)₂] exhibits the highest antioxidant activity and the highest inhibitory effect against the soybean lipogygenase (LOX), properties that are not demonstrated by mefenamic acid. Their inhibitory effects on rat paw edema induced by Carrageenan was studied and compared with those of mefenamic acid. The complex [Zn(mef)₂] exhibited a strong inhibitory effect at 0.1 mmol/Kg B.W. (81.5 ± 1.3% inhibition), superior to the inhibition induced by mefenamic acid at the same dose (61.5 ± 2.3% inhibition). Mefenamic acid and its metal complexes have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse fibroblast L-929 cell line. The copper(II) complex displays against T24, MCF-7 and L-929 cancer cell lines, IC₅₀ values in a μM range similar to that of the antitumor drug cis-platin and they are considered for further stages of screening in vitro and/or in vivo as agents with potential antitumor activity.     

Synthesis,physico-chemical studies of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes with some p-substituted acetophenone benzoylhydrazones and their antimicrobial activity

Complexes of the type [M(pabh)(H₂O)Cl], [M(pcbh)(H₂O)Cl] and [M(Hpabh)(H₂O)₂ (SO₄)] where, M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpabh = p-amino acetophenone benzoyl hydrazone and Hpcbh = p-chloro acetophenone benzoyl hydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra, thermal (TGA & DTA) and X-ray diffraction studies. Co(II), Ni(II) and Cu(II) chloride complexes are square planar, whereas their sulfate complexes have spin-free octahedral geometry. ESR spectra of Cu(II) complexes with Hpabh are axial and suggest as the ground state. The ligand is bidentate bonding through >C = N ? and deprotonated enolate group in all the chloro complexes, whereas, >C = N and >C = O groups in all the sulfato complexes. Thermal studies (TGA & DTA) on [Cu(Hpabh)(H₂O)₂(SO₄)] indicate a multistep decomposition pattern, which are both exothermic and endothermic in nature. X-ray powder diffraction parameters for [Co(pabh)(H₂O)Cl] and [Ni(Hpabh)(H₂O)₂(SO₄)] correspond to tetragonal and orthorhombic crystal lattices, respectively. The ligands as well as their complexes show a significant antifungal and antibacterial activity. The metal complexes are more active than the ligand.     

Metal-based ethanolamine-derived compounds: a note on their synthesis,characterization and bioactivity

Abstract

Metal-based ethanolamines, (L¹)–(L⁴) coordinated with Co(II), Cu(II), Ni(II) and Zn(II) metals in 1:2 (metal:ligand) molar ratio to produce new compounds have been reported. These compounds were screened for their bactericidal/fungicidal activity against a number of bacterial (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus and Bacillus subtilis) and fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) alongside against a shrimp species known as Artemia salina. The screening results indicated that metal complexes have significantly higher activity than uncomplexed ligands against one or more bacterial/fungal species due to chelation. The ligand (L⁴) displayed good bacterial and fungal activity as compared to other ligands. The antibacterial results revealed that the Zn(II) complex (16) of (L⁴) was found to be the most active complex and Co(II) complex (14) of the same ligand (L⁴), demonstrated the highest antifungal activity.     

Syntheses,structures and photoluminescent property of coordination complexes with 2-(1H-1,2,4-triazol-1-yl)acetic acid

Reactions of ligand 2-(1H-1,2,4-triazol-1-yl)acetic acid (HL) with varied metal salts of Cu(II), Co(II), Ni(II), Zn(II), Cd(II) and Ag(I) result in formation of six new coordination complexes, {[Cu(L)₂] · 3H₂O}_n (1), [Co(L)₂(H₂O)₂]_n (2), [Ni(L)₂(H₂O)₂]_n (3), [Zn(L)₂(H₂O)₂]_n, (4), [Cd(L)₂]_n (5) and [Ag(L)]_n (6), and their structures were determined by X-ray crystallography. Complexes 1, 2, 3 and 4 with square-planar or octahedral metal centers have similar two-dimensional (2D) network structure with (4, 4) topology, while complex 5 displays a 2D structure with (6, 3)-connected topology. Complex 6 has a three-dimensional (3D) structure, in which the Ag(I) has tetrahedral coordination geometry. Ligand L^? acts as a 2-connected rod (bridging ligand) in 1, 2, 3 and 4, and acts as 3-connected nodes in 5 and 6. The results indicate that the coordination modes of the ligand and metal centers have great influence on the structures of the complexes. In addition, the photoluminescent properties of ligand HL and complexes 4 and 5 were studied in the solid state at room temperature.     

pH - Specific synthesis, spectroscopic, and structural characterization of an assembly of species between Co(II) and N,N-bis(phosphonomethyl)glycine. Gaining insight into metal-ion phosphonate interactions in aqueous Co(II)-organophosphonate systems

Cobalt involvement in chemical and metallobiological processes entails largely unknown reactivity pathways with a variety of ligands. Such ligands include phosphonate and carboxylate-containing metal ion binders. In an attempt to investigate the nature and properties of species arising from aqueous interactions between Co(II) and N,N-bis(phosphonomethyl)-glycine (H₅NTA2P), reactions between the two led to an assembly of species in (NH₄)₄[Co(H₂O)₆][(H₂O)₂Co(HNTA2P)Co(NH₃)₂(H₂O)₃]₂[Co(NTA2P)(H₂O)₂]₂ · 10H₂O · 1.36CH₃CH₂OH (1) at pH ∼ 5.5. The analytical, spectroscopic and X-ray data on 1 reveal mononuclear and dinuclear complexes of Co(II) surrounded by oxygens, belonging to terminal carboxylates, phosphonates and bound water molecules, and nitrogen atoms from coordinated ammonia and H_xNTA2P^q− (x = 1, q = 4; x = 0, q = 5) ligands. Worth noting is the variable protonation state of the bound diphosphonate ligand and its ability to bridge two Co(II) centers with ostensibly differing coordination spheres. The assembly of three Co(II) species of variable nuclearity and composition attests to the importance of pH-specific conditions, under which “capturing” of more than one species can be achieved for a given Co(II):H₅NTA2P stoichiometry in the presence of ammonia. Collectively, 1 provides a rare glimpse of a “slice” of the aqueous speciation of the binary Co(II)-H₅NTA2P system, while its lattice composition projects key structural features in Co(II)-carboxyphosphonate materials.     

Structural and equilibrium studies on mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) with N-(2-benzimidazolyl)methyliminodiacetic acid and typical N, N donor ligands

Mixed ligand complexes: [Co(L)(bipy)] · 3H₂O (1), [Ni(L)(phen)] · H₂O (2), [Cu(L)(phen)] · 3H₂O (3) and [Zn(L)(bipy)] · 3H₂O (4), where L²⁻ = two -COOH deprotonated dianion of N-(2-benzimidazolyl)methyliminodiacetic acid (H₂bzimida, hereafter, H₂L), bipy = 2,2′ bipyridine and phen = 1,10-phenanthroline have been isolated and characterized by elemental analysis, spectral and magnetic measurements and thermal studies. Single crystal X-ray diffraction studies show octahedral geometry for 1, 2 and 4 and square pyramidal geometry for 3. Equilibrium studies in aqueous solution (ionic strength I = 10⁻¹ mol dm⁻³ (NaNO₃), at 25 ± 1 °C) using different molar proportions of M(II):H₂L:B, where M = Co, Ni, Cu and Zn and B = phen, bipy and en (ethylene diamine), however, provides evidence of formation of mononuclear and binuclear binary and mixed ligand complexes: M(L), M(H₋₁L)⁻, M(B)²⁺, M(L)(B), M(H₋₁L)(B)⁻, M₂(H₋₁L)(OH), (B)M(H₋₁L)M(B)⁺, where H₋₁L³⁻ represents two -COOH and the benzimidazole N₁-H deprotonated quadridentate (O⁻, N, O⁻, N), or, quinquedentate (O⁻, N, O⁻, N, N⁻) function of the coordinated ligand H₂L. Binuclear mixed ligand complex formation equilibria: M(L)(B) + M(B)²⁺ ? (B)M(H₋₁L)M(B)⁺ + H⁺ is favoured with higher π-acidity of the B ligands. For Co(II), Ni(II) and Cu(II), these equilibria are accompanied by blue shift of the electronic absorption maxima of M(II) ions, as a negatively charged bridging benzimidazolate moiety provides stronger ligand field than a neutral one. Solution stability of the mixed ligand complexes are in the expected order: Co(II) < Ni(II) < Cu(II) > Zn(II). The Δ log K_M values are less negetive than their statistical values, indicating favoured formation of the mixed ligand complexes over the binary ones.