Mixed-ligand Cobalt Complexes Research Articles

New cobalt(II) coordination complex for adsorption of Rhodamine B dye and its mechanistic pathway

A new mixed-ligand cobalt complex with the general formula [Co(H2O)(teaH3)(4-NBA)]·(4-NBA)·H2O (1), where (teaH3 = triethanolamine and 4-NBA = 4-nitrobenzoate), has been successfully synthesized and characterized. In this complex, triethanolamine acts as a tetradentate ligand and the 4-NBA act as monodentate ligands. The cobalt metal ion in the complex has a coordination number of 6 with a slightly distorted octahedral geometry. Furthermore, some intramolecular and intermolecular interactions have been observed in 1. Moreover, the kinetic studies on the rate of adsorption confirm that the Pseudo Second Order model accurately predicted the absorption of RhB by the complex. The higher R-squared value and the close agreement between the calculated (Qe = 207.3 mg/g) and experimental (194.4 mg/g) values indicate a satisfactory match. The hydrogen bonding interactions and other weaker electrostatic interactions between the complex and the RhB molecule enhance this adsorption.

Equilibria in the aqueous system of cobalt(II) based on 2-picolinehydroxamic acid and N-(2-hydroxybenzyl)phenylalanine and its ability to inhibit the propagation of cancer cells

Mixed-ligand complexes of cobalt(II) with two bioligands, viz. 2-picolinehydroxamic acid and the reduced Schiff base N-(2-hydroxybenzyl)phenylalanine, were studied in aqueous solution by potentiometry and UV–Vis spectroscopic analysis. The coordination mode of the complexes and their stability were determined and compared to their parent species. Stacking interactions between the rings present in the ligands influence the stability of the complexes. Also, UV–Vis spectroscopy revealed that the stacking interactions affected the intercalation of DNA and mixed-ligand complexes. The in vitro anticancer activity of the free ligand 2-picolinehydroxamic acid and the complexes was tested against cervical and gastric human adenocarcinoma epithelial cell lines. At concentrations of 0.06 and 0.11 mM, the mixed-ligand structures showed the ability to reduce gastric cancer cells with no inhibitory effect on mouse fibroblasts. The cytotoxic effect was accompanied by damage to the cell nuclei, which may confirm that the complexes demonstrate effective binding to DNA. No determination of minimal inhibitory and bactericidal/fungicidal concentrations against the test organisms was possible at higher complex concentrations due to precipitation.

Mixed ligand cobalt and palladium complexes containing triphenylphosphine and a hydrazone: Synthesis and application in non-linear optics

Mixed ligand complexes of cobalt and palladium containing triphenylphosphine and a hydrazone derived from furfural and hydrazine hydrate have been designed, synthesized, evaluated, and characterized from their spectral properties, elemental analysis, and magnetic susceptibility measurements. The spectral techniques suggest that the complexes exhibit square planar geometry. The monomeric properties of the complexes are evaluated from their magnetic susceptibility values. The complexes were subjected to z-scan analysis for third-order non-linear optical measurements. Non-linear transmission measurements performed using laser pulses at 532 nm in nanosecond indicate that the complexes may show good potential as optical limiters.

Mono and binuclear cobalt(II) mixed ligand complexes containing 1,10-phenanthroline and adenine using 1,3-diaminopropane as a spacer: synthesis, characterization, and antibacterial activity investigations

BackgroundCoordination compounds, in particular cobalt(II) mixed ligand complexes containing 1,10-phenantroline, have drawn the attention of many investigators as some of them are showing antimicrobial activities.ResultHerein, we report three novel mixed ligand complexes of cobalt(II) having the formulae [Co(L1)2(H2O)2]Cl2, [Co(L1)2(L2)(H2O)]Cl2 and [Co2(L1)4(L2)2(L3)]Cl4 (L1 = 1,10-phenanthroline, L2 = adenine, L3 = 1,3-diaminepropane) were synthesized and characterized by elemental analysis, conductivity measurement, infrared, and UV-Vis spectroscopic techniques. Octahedral geometries are proposed to all the complexes. In vitro antibacterial activities of the ligands, salt, and metal complexes were tested on four pathogenic bacteria (Staphylococcus aureus, Salmonella typhus, Escherichia coli, and Staphylococcus epidermis) using disc diffusion method.ConclusionsIt is interesting to note that the newly synthesized cobalt(II) complexes are active against gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) even though cobalt(II) complexes are well known for their activity against gram positive bacteria.

Synthesis, characterization and thermal properties of 1,10-phenanthroline mixed-ligand complexes of cobalt(II) and copper(II): metal-mediated transformations of the dicyanamide ion

The reaction of 1,10-phenanthroline and dicyanamide ligands with Cu(II) and Co(II) nitrates afforded the complexes [Cu(phen)(BMCA)](NO3)] (1) and [Co(phen)2(NO3)](dcg-)·(H2O) (2). The dicyanamide anion was transformed in 1 and 2 to bis(methoxycarbimido)aminato (BMCA) and dicyanoguanidinate (dcg) anions, respectively. The complexes were characterized by elemental analysis, infrared spectroscopy and ultraviolet–visible spectroscopy, magnetic susceptibility measurement and X-ray crystallography. Both complexes crystallize in the monoclinic crystal system, and the structures are stabilized by extended hydrogen bonding networks as well as aromatic π–π stacking interactions. The thermal and antimicrobial properties of the complexes have also been evaluated. Density functional theory calculations were also performed in order to gain insights into the molecular interactions in the synthesized compounds and to predict some of their electronic properties.

Solvent Extraction of Cobalt (II) with 2, 6-dithiolphenol and its Derivatives in the Presence of Hydrophobic Amines

Mixed-ligand complexes of Cobalt(II) with dithiolphenol (DP) {2, 6-dithiolphenol (DTP) and its derivatives (2, 6-dithiol-4-methylphenol (DTMP), 2, 6-dithiol-4-propylphenol (DTPP), 2, 6-dithiol-4-tert-buthylphenol (DTBP)} in the presence of aminophenols (AP) have been studied by spectrophotometry. Extraction of mixed ligand complexes is maximal at pH 4.1-6.5. The optimal conditions for the formation and extraction of mixed-ligand compounds have been found and the ratios of components I the complexes have been determined. The Beer’s law was applicable in the range of 0.2-20 μg/ml. The effect of foreign ions and reagents on the extraction was studied. The method is free from common interferences. A procedure has been developed for extraction – spectroand#172;photometric determination cobalt in different objects (in steel, sewage water, bottom sediments, food and soil samples).

Solvent Extraction of Cobalt (II) with 2, 6-dithiolphenol and its Derivatives in the Presence of Hydrophobic Amines

Mixed-ligand complexes of Cobalt(II) with dithiolphenol (DP) {2, 6-dithiolphenol (DTP) and its derivatives (2, 6-dithiol-4-methylphenol (DTMP), 2, 6-dithiol-4-propylphenol (DTPP), 2, 6-dithiol-4-tert-buthylphenol (DTBP)} in the presence of aminophenols (AP) have been studied by spectrophotometry. Extraction of mixed ligand complexes is maximal at pH 4.1-6.5. The optimal conditions for the formation and extraction of mixed-ligand compounds have been found and the ratios of components I the complexes have been determined. The Beer’s law was applicable in the range of 0.2-20 μg/ml. The effect of foreign ions and reagents on the extraction was studied. The method is free from common interferences. A procedure has been developed for extraction – spectroand#172;photometric determination cobalt in different objects (in steel, sewage water, bottom sediments, food and soil samples).

Syntheses, Structures, and Magnetic Properties of Mixed-ligand Complexes of Co(II) Based on N-Heterocyclic and Different Carboxylate Ligands

Two novel transition-metal coordination polymers with the formulas [Co(L1)(bbi)(H2O)]n (1) and {[Co(L2)(phen)]·H2O}n (2) (H2L1 = 1,4-naphthalenedi- carboxylic acid, H2L2 = 5-OH-1,3-benzenedicarboxylic acid, bbi = 1,1′-(1,4-butanediyl)bis(imidazole), phen = 1,10-phenanthroline) have been hydrothermally synthesized and characterized by techniques of single crystal X-ray diffraction, infrared spectra, elemental analysis, powder X-ray diffraction, and variable-temperature magnetic susceptibility measurements. X-ray crystal structure analyses reveal that complex 1 exhibits 2D framework with 4-connected sql topology and is further extended into a 3D supramolecular architecture via strong O–H···O and weak C–H···O hydrogen-bonding interactions, while complex 2 features a 1D ladder-like chain with a 3-connected (42·6) topological structure. Magnetic studies showed the presence of an antiferromagnetic interaction between adjacent Co(II) ions in both complexes. Two new mixed ligand complexes of cobalt based on N-heterocylic and carboxylate ligands were readily obtained and characterized. The topological structures, thermal stabilities and magnetic properties of which are observed and discussed.

Synthesis, structural investigation and biological application of new mono- and binuclear cobalt (II) mixed-ligand complexes containing 1,10-phenanthroline, acetamide and ethylenediamine

The intensive use of antibiotics has led to an increase of drug resistant bacteria against known antibiotics. To overcome the alarming problem of microbial resistance to antibiotics, the discovery of novel active compounds against new targets is a matter of urgency. Based on this, we report three new mixed ligand complexes of cobalt (II) viz. mononuclear ([Co(phen) 2 (Act)(H 2 O)]Cl 2 .H 2 O and [Co(phen) 2 (Act)(en)]Cl 2 ), and binuclear [Co 2 (phen) 4 (Act) 2 (en)]Cl 4 which were synthesized from CoCl 2 .6H 2 O, 1,10-phenanthroline monohydrate, acetamide and ethylenediamine. These complexes were characterized using spectroscopic (ESI-MS, ICP-OES, FT-IR, and UV-Vis), chloride determination as well as melting point and conductance measurement. Invitro antibacterial activity was also tested on two Gram positive ( Staphylococcus aureus , Streptococcus pyogenes ) and two Gram negative ( Escherichia coli and Klebsiella pneumoniae ) bacteria using disc diffusion method. The complexes performed well even against the Gram-negative bacteria. The antibacterial result was found comparable with the commercial drug Gentamicin even at lower concentration of complexes. Thus, the synthesized complexes may be considered as potential antibacterial agents after passing cytotoxicity testing.

Computational modeling of mixed-ligand cobalt complexes with o-quinone derivative of corannulene

The structure and energy characteristics of isomers of electrically neutral adducts of tetracoordinate cobalt complexes with o-quinone derivative of corannulene were studied quantum chemically within the density functional theory (DFT) in the UB3LYP*/6-311++G(d,p) approximation. It was shown that the framework rigidity of the redox-active ligand favors convergence of the energy levels of the high-spin and low-spin isomers of the complexes under study as compared to the o-benzoquinone-containing analogues. At the same time, steric strain in the corannulene moiety causes the stability of the adducts to reduce. A compound characterized by high stabilization energy and the ability to switch its spin states via valence tautomeric rearrangements was found by systematic variation of structural parameters of cobalt bis(chelate).

Вплив змішанолігандного комплексу кобальту на його обмін у організмі високопродуктивних корів

<p>In the scientific and economic research we investigated the influence different levels of mixed ligand complex of Cobalt on milk productivity and its exchange in the organism of highly productive cows of Ukrainian Black-and-White milk breed in combination with sulfates: Zinc 650 g/t, potassium 38 g/t, sodium selenite 1.8 g/t. For cows of the 1st control group, we administrated 8.9 g/t of cobalt sulfate, 2nd group – 9.7 g/t of mixed ligand complex of cobalt, 3rd, 4th and 5th experimental groups respectively, were fed into rations, g/t: 7.3; 4.9, and 2.4. As a result, the cows of the 1st control group and the 2nd experimental group the deficit in Cobalt was eliminated 100 % to the current norm, and for cows of the 3rd, 4th and 5th experimental groups - 75, 50 and 25 %.<br />The conducted researches have proved that the highest average daily milk yield of natural fat had cows of the 3rd experimental group, which consumed mixed fodder in the composition of mixed ligand complex of Cobalt in the amount of 75 % by concentration of the metal, which prevailed the analogues of the control group for this indicator, respectively, by 4.4 kg (р≤0.01), or by 9.7%. Cows of the 2nd, 4th and 5th experimental groups according to the average daily milk fat content of the natural fat were dominated by analogues of control, respectively, by 2.1 kg or 4.8 %; 3.2 kg or 7.1% (p≤0.05); and 1.3 kg, or 2.9 %. During the experiment, fat content of milk of cows of the 3rd experimental group exceeded fat content of milk of control group of cows by 0.03%, and in terms of milk, the 4% fat content milk yield was 3649.7 kg, which is 10.8 % (p≤0.01) higher yields of experimental cows in the control group. As for the content of protein in milk, there was no significant difference between the groups in this indicator. The use of sulfuric acid Cobalt in accordance with the recommended norm in the diet of experimental cows resulted in its positive balance in the body at 4.87 mg per head per day. And in the cows of the 2-5th experimental groups who ate this trace in the form of a mixed ligand complex the balance was, respectively, 8.19 % (p≤0.01), 10.07 (p≤0.01), 8.89 (p≤0.01), and 8.05 (p≤0.01).</p>

Synthesis, characterization and biological properties of mixed ligand complexes of cobalt(II/III) valproate with 2,9‐dimethyl‐1,10‐phenanthroline and 1,10‐phenanthroline

The synthesis of mononuclear cobalt(II/III) complexes with two different ligands (complex 2: [Co(valp)2(2,9‐dmp)] and complex 3: [Co(valp)2(H2O)(1,10‐phen)]) was investigated and the characterization of both complexes was achieved using IR, UV–Vis, and single crystal X‐ray diffraction. Using single crystal X‐ray diffraction, the crystal structure of each of the complexes was determined. Additionally, the biological activity of these complexes was studied in five gram‐positive and four gram‐negative bacterial strains. Whereas in all gram‐negative bacteria tested, cobalt valproate complexes did not show any anti‐bacterial activity, both complexes had effects on gram positive bacteria. Complex 2 demonstrated good anti‐bacterial activity against all gram‐positive bacteria with inhibition zone diameter (IZD) ranging between 15–28 mm. Complex 3 exhibited low inhibition activity against all gram‐positive bacteria except E. faecalis with IZD ranging between 11.3–13.7 mm. Moreover, as an indication of its uses as industrial catalyst, the rate of bis(p‐nitrophenyl) phosphate (BNPP) hydrolysis when catalyzed by these complexes was measured at different temperatures, concentrations and pH. Complex 2 proved to be a better catalyst to induce the hydrolysis of BNPP.

Mixed ligand complexes of cobalt(III) and iron(III) containing N2O2-chelating Schiff base: Synthesis, characterisation, antimicrobial activity, antioxidant and DFT study

Six mixed ligand complexes, namely, [Co(acac)L1] (1), [Fe(acac)L1] (2), [Co(acac)L2] (3), [Fe(acac)L2] (4), [Co(acac)L3] (5), and [Fe(acac)L3] (6) (H2L1 = NN/-bis(salicylidene)-trans 1,2 diaminocyclohexane, H2L2 = NN/-bis(salicylidene)-1,2 phenylenediamine, H2L3 = NN/-bis(salicylidene)-4-methyl-1,2-phenylenediamine) were synthesised and characterized using elemental analysis, IR spectra, UV–Vis spectra, mass spectra, magnetic susceptibility measurements, 1H and 13C NMR spectroscopy, thermogravimetric analysis. The molar conductance measurement confirmed the non-electrolytic nature of the complexes in DMF solution. Antioxidant activity of the complexes was studied using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging method. Biological studies of the complexes have been carried out in vitro for antimicrobial activity against some selected gram-positive and gram-negative bacteria. DFT calculations were performed using GAUSSIAN 09 program to ascertain the stable electronic structure, HOMO-LUMO energy gap, chemical hardness and dipole moment of the complexes.

Mixed-ligand cobalt(II) complexes of bioinorganic and medicinal relevance, involving dehydroacetic acid and β-diketones: Their synthesis, hyphenated experimental-DFT, thermal and bactericidal facets

The present report pertains to synthesis and combined experimental-DFT studies of a series of four novel mixed-ligand complexes of cobalt(II) of the general composition [Co(dha)(L)(H2O)2], where dhaH=dehydroacetic acid, LH=β-ketoenolates viz., o-acetoacetotoluidide (o-aatdH), o-acetoacetanisidide (o-aansH), acetylacetone (acacH) or 1-benzoylacetone (1-bac). The resulting complexes were formulated based on elemental analysis, molar conductance, magnetic measurements, mass spectrometric, IR, electronic, electron spin resonance and cyclic voltammetric studies. The TGA based thermal behavior of one representative complex was evaluated. Molecular geometry optimizations and vibrational frequency calculations have been performed with Gaussian 09 software package by using density functional theory (DFT) methods with B3LYP/LANL2MB combination for dhaH and one of its complexes, [Co(dha)(1-bac)(H2O)2]. Theoretical data has been found in an excellent agreement with the experimental results. Based on experimental and theoretical data, suitable trans-octahedral structure has been proposed for the present class of complexes. Moreover, the complexes also showed a satisfactory antibacterial activity.

Magnetic and Spectral Studies on 4-Methylpiperazine-1-carbodithioate and 1,10-Phenenthroline or 2,2′-Bipyridyl Mixed-Ligand Complexes of Cobalt(II), Nickel(II) and Copper(II)

Some mixed-ligand complexes of 4-methylpiperazine-1-carbodithioate (4-MPipzcdt) having the general formulae, viz. [M(4-MPipzcdtX)a(L)b]Y (M = Co(II), Ni(II), Cu(II); L = 1,10-phenanthroline (phen) or 2,2′-bipyridyl (bipy); X = H when Y = Cl2,a = 2, b = 1; X = nil where Y = Cl when a = 1, b = 2 and Y = nil when a = 2, b = 1) have been prepared and characterized by elemental analyses, molar conductance, infrared and electronic absorption spectral, and magnetic susceptibility measurements at different temperatures. Cobalt(II) complexes exhibit superexchange ferromagnetic coupling of the unpaired spins on adjacent low-spin cobalt(II) species forming long chained polymeric compounds. Nickel(II) complexes with chromophores [NiS4N2] and [NiS2N4] are being assigned cis-distorted octahedral geometries. Copper(II) complexes have been proposed to have six-coordinate tetragonal structures.

Mononuclear Co(III) and Ni(II) Complexes with Polypyridyl Ligands, [Co(phen)2(taptp)]3+ and [Ni(phen)2(taptp)]2+: Synthesis, Photocleavage and DNA-binding

Two novel, mixed ligand complexes of cobalt(III) and nickel(II), [Co(phen)2(taptp)](3+) (1) and [Ni(phen)2(taptp)](2+) (2) (phen = 1,10-phenanthroline and taptp = 4,5,9,18-tetraazaphenanthreno [9,10-b]triphenylene), were synthesized and characterized by elemental analyses, UV-visible and NMR spectroscopies. The binding interactions of the two complexes with DNA have been investigated using absorption and emission spectroscopy methods and electrophoresis measurement mode. The intrinsic binding constants for these complexes to DNA are in the order of 10(5). In Tris buffer, the Co(III) complex shows a moderate luminescence which was enhanced after binding to DNA. However for complex Ni(II), no emission was observed in Tris buffer. The [Co(phen)2(taptp)](3+) and [Ni(phen)2(taptp)](2+) can cause the photocleavage of DNA supercoiled pBR322 upon irradiation by 360nm light. Based on the data, an intercalative mode of DNA binding is suggested for the two complexes.

Synthesis, spectral characterization, DNA interaction studies, anthelmintic and antimicrobial activity of transition metal complexes with 3-(2- hydroxybenzylideneamino)-2-methylquinazolin-4(3H)-one and 1,10- phenanthroline

Mixed ligand complexes of cobalt(II) (1), copper(II) (2) and oxovanadium(IV) (3) with 3- (2-hydroxy benzylideneamino)-2-methylquinazolin-4(3H)-one and 1,10-phenanthroline have been synthesized and characterized by elemental analyses, IR, electronic, 1 H-NMR, mass spectra, molar conductance and thermal studies. The synthesized compounds were screened for their in vitro antimicrobial activity. The results show a significant increase in antimicrobial activity of the complexes compared to ligand. Antihelmintic activity of the compounds has been tested on earthworms and the enhanced activity was observed upon complexation. In addition, DNA binding and DNA cleavage studies for the newly prepared compounds were also studied. These studies indicate that the DNA binding and cleavage efficacy were increased in the complexes relative to the parental ligand.

Synthesis, structure, and dynamics of mixed-ligand cobalt complexes with redox-active phenoxazin-1-one

155 Considerable interest in studying the structure and dynamics of bistable transition metal complexes with redox active (non innocent) ligands stems from the possibility to design quick response magnetically active molecular switches and energy independent molecular memory [1–3]. The mechanism of ther mally or photochemically controlled rearrangements of such complexes (redox isomerism or valence tau tomerism) is determined by intramolecular electron transfer between energetically closely spaced d orbitals of the central atom and the frontier orbitals of the ligand. In the most general way, these conditions are achieved in hexacoordinated d4–d7 metal complexes with sterically protected о quinone or о quinone imine ligands in different oxidation states in which the coordinative saturation of the central ion is ensured by introducing a neutral bidentate ligand [4, 5]. Another approach to the synthesis of potentially valence tautomeric metal complexes, used in the present work, involves the interaction of a stable tetra coordinated metal complex with a bidentate redox active ligand. Previously, mixed ligand bis(acetylacet onato)ruthenium complexes with о iminoquinone, о iminothioquinone, and о diiminoquinones (1a) were synthesized [6, 7]. With the ligands of the last type, chromium complexes (1b) have been recently obtained [8]. Adducts of о quinone and phenan threnequinone with Fe(salen) (2) are known [9].

Polymeric and mixed ligand complex of cobalt(II) and 4-hydroxybenzhydrazide: Crystal structure and vibrational spectroscopy

Reaction of CoSO 4 and 4-hydroxybenzhydrazide in water/methanol solution resulted in polymeric complex with C O and NH 2 groups of organic ligand, two water molecules and two oxygen atoms of two sulfate anions in metal coordination sphere. The X-ray analysis revealed that the complex is in the form of polymer chain of the helical structure formed due to sulfate bridge geometry and intra-chain hydrogen bonds. The variety of coordinated ligands is reflected in the vibrational spectra where six different metal–ligand modes were found. The bands related to stretching and bending vibrations of NH 2, NH, OH groups as well as water molecules were located with help of hydrogen–deuterium substitution. For proposed band assignment the animation of DFT calculated normal modes was employed.

Biimidazole containing cobalt(iii) mixed ligand complexes: Crystal structure and photonuclease activity

Two new mixed ligand complexes of cobalt(iii) containing ancillary biimidazole ligands, [Co(phen)(2)H(2)biim](ClO(4))(3).0.5(H(7)O(3))(ClO(4)) (1) and [Co(bpy)(2)H(2)biim](ClO(4))(3).3H(2)O (2) have been synthesized and characterized by various spectroscopic and electrochemical techniques. Both complexes and , have been characterized by the single crystal X-ray diffraction method. While cobalt complex was found to crystallize in the triclinic system with the P1[combining macron] space group, complex was found to crystallize in the orthorhombic system with the Pbca space group. The unit cell packing of complex shows the presence of a water cluster, which is buttressed by oxygen atoms present in the perchlorate anions and water with an average OO bond distance of 2.41-2.86 A. Interaction of these complexes with calf thymus DNA (CT-DNA) was investigated by electronic spectral titrations. The results suggest that complexes and bind to DNA through the groove via hydrogen bonding. This is due to the presence of -NH in the ancillary ligand biimidazole, which favors hydrogen bonding with DNA base pairs. The intrinsic DNA binding constant values for complexes and were found to be (5.18 +/-0.23) x 10(4) M(-1) and (1.26 +/- 0.13) x 10(4) M(-1) respectively. Groove binding of these complexes with DNA is further supported by viscosity measurements, thermal denaturation and circular dichroism studies. Among the two cobalt complexes, complex possesses greater DNA binding strength due to the presence of the conjugated aromatic structure of the phen ligand which increases the hydrophobic interactions with DNA. DNA cleavage experiments using plasmid DNA pUC 18 show that these complexes exhibit efficient photonuclease activity in the presence of molecular oxygen.