Cu(II), Ni(II) and Zn(II) mononuclear building blocks based on new polynucleating azomethine ligand : Synthesis and characterization
Five new mononuclear complexes formed by the polynucleating ligand 2-[1-(3,5-dimethyl)pyrazolyl]-2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene]acetohydrazide (HL): [Ni(L)(HL)]ClO4·2CH3OH (1), [Ni(L)2]·CH3OH (2), [Zn(L)(HL)]ClO4·2CH3OH (3), [Zn(L)2]·CH3OH (4) and [Cu(L)2]·CH3OH (5) were synthesized and characterized by elemental analysis, mass-spectrometry, IR-spectroscopy and X-ray analysis. The complexes reveal distorted octahedral N4O2 coordination arrangement formed by both protonated and deprotonated (1, 3) or two deprotonated ligand molecules (2, 4, 5). The presence of non-coordinated oxime and pyrazole groups resulted in the formation of extensive systems of hydrogen bonds in the crystal…
[Diaquasesqui(nitrato-κO)hemi(perchlorato-κO)copper(II)]-μ-{bis[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide}-[triaqua(perchlorato-κO)copper(II)] nitrate monohydrate
In the binuclear title complex, [Cu2(ClO4)1.5(NO3)1.5(C18H16N6Se)(H2O)5]NO3·H2O, both CuII ions are hexacoordinated by O and N atoms, thus forming axially elongated CuO4N2 octahedra. The equatorial plane of each octahedron is formed by one chelating pyrazole–pyridine fragment of the organic ligand and two water molecules. The axial positions in one octahedron are occupied by a water molecule and a monodentately coordinated perchlorate anion, while those in the other are occupied by a nitrate anion and a disordered perchlorate/nitrate anion with equal site occupancy. The pyrazole–pyridine units of the organic selenide are trans-oriented to each other with a C—Se—…
A Bis(mu-phenoxo)-Bridged Dizinc Complex with Hydrolytic Activity
The dinuclear complex [Zn2(papy)2]·2CH3OH [H2papy = N- (2-hydroxybenzyl)-N-(2-picolyl)glycine] was synthesized and characterized. The crystal structure of the complex reveals that both ZnII ions are pentacoordinate with distorted pentagonal bipyramidal coordination arrangements. The phenoxyl groups of each ligand bridge the two metal atoms, whereas each carboxylate of the ligand is terminally bound to one ZnII ion. Potentiometric studies of the ZnII:H2papy system in a methanol/water mixture show the existence of a mononuclear species at lower pH; but at a pH above 5, a dimeric species starts to dominate and transforms further into a bis(μ-phenoxo) bridged dizinc complex by deprotonation of …
Coordination Diversity in Mono- and Oligonuclear Copper(II) Complexes of Pyridine-2-Hydroxamic and Pyridine-2,6-Dihydroxamic Acids
Solution and solid state studies on Cu(II) complexes of pyridine-2-hydroxamic acid (HPicHA) and pyridine-2,6-dihydroxamic acid (H2PyDHA) were carried out. The use of methanol/water solvent allowed us to investigate the Cu(II)-HPicHA equilibria under homogeneous conditions between pH 1 and 11. In agreement with ESI-MS indication, the potentiometric data fitted very well with the model usually reported for copper(II) complexes of α-aminohydroxamate complexes ([CuL](+), [Cu5(LH-1)4](2+), [CuL2], [CuL2H-1](-)), however with much higher stability of the 12-MC-4 species. A series of copper(II) complexes has been isolated in the solid state and characterized by a variety of spectroscopic methods, …
Chiral spin crossover nanoparticles and gels with switchable circular dichroism
Spin crossover complexes represent spectacular examples of molecular switchable materials. We describe a new approach towards homochiral coordination nanoparticles of [Fe(NH2trz)3](L-CSA)2 (NH2trz = 4-amino-1,2,4-triazole, L-CSA = L-camphorsulfonate) that display an abrupt switch of chiral properties associated with a cooperative spin transition. This is an original method that generates stable and additive-free colloidal solutions of nanoparticles with a spin transition around room temperature. The introduction of a chiral anion to the coordination framework makes these nanoparticles display specific chiro-optical (circular dichroism) properties that are different in high and low spin stat…
Influence of structural elements on iron(III) chelating properties in a new series of amino acid-derived monohydroxamates
Abstract A series of amino acid-derived monohydroxamate compounds A1 – A7 was synthesized and characterized for their coordination properties of Fe(III). The series varies in their skeletal lengths and compositions; some compounds lack external substituents, others are substituted with external functional amino or carboxylic groups, or alternatively inert methyl. Undertaken investigations allowed the determination of stoichiometry, stability constants and spectroscopic parameters of formed ferric complexes. Incorporation of an external functional group with a dissociable proton affects the coordination behavior; the presence of carboxylic or amino groups hampers the formation of mono-, di- …
Exploring the Specificity of Rationally Designed Peptides Reconstituted from the Cell-Free Extract of Deinococcus radiodurans toward Mn(II) and Cu(II)
A series of five rationally designed decapeptides [DEHGTAVMLK (DP1), THMVLAKGED (DP2), GTAVMLKDEH (Term-DEH), TMVLDEHAKG (Mid-DEH), and DEHGGGGDEH (Bis-DEH)] have been studied for their interactions with Cu(II) and Mn(II) ions. The peptides, constructed including the most prevalent amino acid content found in the cell-free extract of Deinococcus radiodurans (DR), play a fundamental role in the antioxidant mechanism related to its exceptional radioresistance. Mn(II) ions, in complex with these peptides, are found to be an essential ingredient for the DR protection kit. In this work, a detailed characterization of Cu(II) systems was included, because Cu(II)–peptide complexes have also shown r…
[Aquabis(nitrato-κO)copper(II)]-μ-{bis[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl]selenide}-[diaqua(nitrato-κO)copper(II)] nitrate monohydrate
In the title binuclear complex, [Cu2(NO3)3(C18H16N6Se)(H2O)3]NO3·H2O, the CuII ions are pentacoordinated in a tetragonal–pyramidal geometry. In both cases, the equatorial planes are formed by a chelating pyrazole-pyridine group, a water molecule and a nitrate O atom, whereas the apical positions are occupied by a water molecule for one CuII ion and a nitrate O atom for the other. The organic selenide ligand adopts a trans configuration with respect to the C–Se–C plane. Numerous intermolecular O—H...O and N—H...O hydrogen bonds between the coordinating and lattice water molecules, nitrate anions and pyrazole groups are observed. &…
[Aquabis(nitrato-κO)copper(II)]-μ-{bis[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl]selenide}-[diaqua(nitrato-κO)copper(II)] nitrate monohydrate
In the title binuclear complex, [Cu2(NO3)3(C18H16N6Se)(H2O)3]NO3·H2O, the Cu(II) ions are penta-coordinated in a tetra-gonal-pyramidal geometry. In both cases, the equatorial planes are formed by a chelating pyrazole-pyridine group, a water mol-ecule and a nitrate O atom, whereas the apical positions are occupied by a water mol-ecule for one Cu(II) ion and a nitrate O atom for the other. The organic selenide ligand adopts a trans configuration with respect to the C-Se-C plane. Numerous inter-molecular O-H⋯O and N-H⋯O hydrogen bonds between the coordinating and lattice water mol-ecules, nitrate anions and pyrazole groups are observed. π-π stacking inter-actions between the pyridine rings [av…
Bis[3-methyl-5-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide methanol hemisolvate
The asymmetric unit of the title compound, C18H16N6Se·0.5CH3OH, contains two independent molecules of bis[3-methyl-5-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide with similar C—Se—C bond angles [99.30 (14) and 98.26 (13)°], and a methanol molecule of solvation. In one molecule, the dihedral angles between pyrazole and neighbouring pyridine rings are 18.3 (2) and 15.8 (2)°, and the corresponding angles in the other molecule are 13.5 (2) and 8.3 (2)°. In the crystal, the selenide and solvent molecules are linked by classical O—H...N and N—H...N hydrogen bonds, as well as by weak C—H...O and C—H...π interactions, forming a three-dimensional supramolecular architecture.
Complex formation of copper(II), nickel(II) and zinc(II) with ethyl phosphonohydroxamic acid : solution speciation, synthesis and structural characterization
The first example of a Cu(II) 12-MC-4 hydroxamic metallacrown containing an ethylphosphonate group as an additional donor function in the β-position with respect to the hydroxamic group is described. The solution equilibrium of ethylphosphonoacetohydroxamic acid (PAHEt) with Cu(II) was investigated in aqueous solution by a combination of potentiometry, mass spectrometry, UV-Vis and EPR spectroscopies, and isothermal titration calorimetry. A model containing mononuclear [CuL], [CuL2]2− and [CuL2H−1]3− and pentanuclear [Cu5(LH−1)4]2− species is proposed. The predominance of the [Cu5(LH−1)4]2− species in solution over the pH range 4–9 was confirmed by the signals present in the ESI-MS spectra,…
Indefinitely stable iron(IV) cage complexes formed in water by air oxidation
In nature, iron, the fourth most abundant element of the Earth's crust, occurs in its stable forms either as the native metal or in its compounds in the +2 or +3 (low-valent) oxidation states. High-valent iron (+4, +5, +6) compounds are not formed spontaneously at ambient conditions, and the ones obtained synthetically appear to be unstable in polar organic solvents, especially aqueous solutions, and this is what limits their studies and use. Here we describe unprecedented iron(IV) hexahydrazide clathrochelate complexes that are assembled in alkaline aqueous media from iron(III) salts, oxalodihydrazide and formaldehyde in the course of a metal-templated reaction accompanied by air oxidation…
[Di-aqua-sesqui(nitrato-κO)hemi(perchlorato-κO)copper(II)]-μ-{bis-[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide}-[tri-aqua-(perchlorato-κO)copper(II)] nitrate monohydrate.
In the binuclear title complex, [Cu2(ClO4)1.5(NO3)1.5(C18H16N6Se)(H2O)5]NO3·H2O, both Cu(II) ions are hexa-coordinated by O and N atoms, thus forming axially elongated CuO4N2 octa-hedra. The equatorial plane of each octa-hedron is formed by one chelating pyrazole-pyridine fragment of the organic ligand and two water mol-ecules. The axial positions in one octa-hedron are occupied by a water mol-ecule and a monodentately coordinated perchlorate anion, while those in the other are occupied by a nitrate anion and a disordered perchlorate/nitrate anion with equal site occupancy. The pyrazole-pyridine units of the organic selenide are trans-oriented to each other with a C-Se-C angle of 96.01 (14)…
Crystal structure of meso-tetrakis(4-nitrophenyl)porphyrin nitrobenzene disolvate
The porphyrin core of the title centrosymmetric compound, C44H26N8O8·2C6H5NO2, is approximately planar, the maximum deviation being 0.069 (3) Å. The planes of the benzene rings of the nitrophenyl substituents are almost perpendicular to the porphyrin mean plane, making dihedral angles of 73.89 (9) and 89.24 (9)°. The two pyrrole ring H atoms are equally disordered over the four pyrrole ring N atoms. In the crystal, weak C—H...O and C—H...N hydrogen bonds link the porphyrin molecules into a three-dimensional supramolecular network. The nitrobenzene solvent molecules are linked by weak C—H...O hydrogen bonds into supramolecular chains propagating along thea-axis direction.
Handbook of Metal-Microbe Interactions and Bioremediation
Around the World, metal pollution is a major problem. Conventional practices of toxic metal removal can be ineffective and/or expensive, delaying and exacerbating the crisis. Those communities dealing with contamination must be aware of the fundamentals advances of microbe-mediated metal removal practices because these methods can be easily used and require less remedial intervention. This book describes innovations and efficient applications for metal bioremediation for environments polluted by metal contaminates.
Cyclic Analogs of Desferrioxamine E Siderophore for 68Ga Nuclear Imaging: Coordination Chemistry and Biological Activity in Staphylococcus aureus
As multidrug-resistant bacteria are an emerging problem and threat to humanity, novel strategies for treatment and diagnostics are actively sought. We aim to utilize siderophores, iron-specific strong chelating agents produced by microbes, as gallium ion carriers for diagnosis, applying that Fe(III) can be successfully replaced by Ga(III) without losing biological properties of the investigated complex, which allows molecular imaging by positron emission tomography (PET). Here, we report synthesis, full solution chemistry, thermodynamic characterization, and the preliminary biological evaluation of biomimetic derivatives (FOX) of desferrioxamine E (FOXE) siderophore, radiolabeled with 68Ga …
Complex formation of copper( ), nickel( ) and zinc( ) with ethylophosphonoacetohydroxamic acid: solution speciation, synthesis and structural characterization
We present herein the thermodynamic and X-ray characterisation of a novel ethyl phosphonohydroxamic acid-based Cu( ) metallacrown, predominating in solution in a broad pH range.
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