Coordination arrays — Synthesis and characterization of tetranuclear complexes of grid-type

2004 ◽  
Vol 82 (10) ◽  
pp. 1428-1434 ◽  
Author(s):  
Garry S Hanan ◽  
Dirk Volkmer ◽  
Jean-Marie Lehn
Keyword(s):  
Metal Ions ◽  
Self Assembly ◽  
Metal Ion ◽  
Transition Metal Ions ◽  
Tridentate Ligands ◽  
H Nmr ◽  
Nitrogen Ligands ◽  
Metal Metal ◽  
Tetranuclear Complexes

A series of tetranuclear metal complexes of grid-type consisting of four bis-tridentate ligands and four divalent transition metal ions were synthesized and characterized. The 1H NMR spectra of diamagnetic complexes containing Zn(II), Cd(II), Fe(II), and Ru(II) was correlated to the radius of the metal ion. The UV–vis and electrochemical results indicated that the bridging ligand π* orbital and the dπ metal orbital are stabilized by complexation of more than one metal ion. Furthermore, the Co(II) and Fe(II) grids exhibit metal–metal interaction mediated by the bis-tridentate ligands as indicated by electrochemical and spectroscopic methods. These results provide guidelines for the design of larger grids bearing several metal centres in a square arrangement, which also represent potential components of molecular electronic devices.Key words: complexes with nitrogen ligands, octahedral metal ions, self-assembly, supramolecular chemistry.

scholarly journals Characterization of Chromium-tris(catecholate) Complex: A Theoretical Study

2017 ◽  
Vol 65 (2) ◽  
pp. 113-117
Author(s):  
Mohammad A Matin ◽  
Mazharul M Islam ◽  
Mohammed A Aziz
Keyword(s):  
Binding Energy ◽  
Transition Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Hybrid Approach ◽  
Transition Metal Ions ◽  
Electronic Band ◽  
Catecholate Complex ◽  
Electronic Band Gap

Phenolic compounds generally have special smell and are easily soluble in water, organic solvents (alcohols, esters, chloroform, ethyl acetate) and in alkali. Phenols produce coloured complexes with heavy metal ions, such as with chromium ion. The molecular details underlying the cross-linking mediated by transition metal ions are largely unknown. Using HF/DFT hybrid approach B3LYP, this study examines the structure, binding energy, spectroscopic and electronic properties of complex formed by the attachment of Cr3+ with a catechol ligand. Our study shows that the binding of Cr3+ with the catechol ligand is not as strong as the binding of other metal ions with catechol.The calculated FTIR spectra show strong IR intensities due to large charge polarization. The UV-Vis absorption spectrum of the tris-catecholato-Cr3+complex shows a clear ligand-to-metal charge transfer. The calculated electronic band gap is 4.06 eV which is in the range of transition metal ion tris-catechol complexes. Thermodynamic properties studied in this work show that the metal ion-ligand binding energy (532.99 kcal/mol) is close to those of the hexa-aqua complexes (ranging from 540 to 553 kcal/mol). Dhaka Univ. J. Sci. 65(2): 113-117, 2017 (July)

scholarly journals Hypochlorite and superoxide radicals can act synergistically to induce fragmentation of hyaluronan and chondroitin sulphates

2004 ◽  
Vol 381 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Martin D. REES ◽  
Clare L. HAWKINS ◽  
Michael J. DAVIES
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Transition Metal Ions ◽  
Chloride Ions ◽  
Superoxide Radicals ◽  
Thermal Source ◽  
Site Specific ◽  
Trace Metal Ions ◽  
Electron Reduction ◽  
Polymer Fragmentation

Activated phagocytes release the haem enzyme MPO (myeloperoxidase) and also generate superoxide radicals (O2•−), and hence H2O2, via an oxidative burst. Reaction of MPO with H2O2 in the presence of chloride ions generates HOCl (the physiological mixture of hypochlorous acid and its anion present at pH 7.4). Exposure of glycosaminoglycans to a MPO–H2O2–Cl− system or reagent HOCl generates long-lived chloramides [R-NCl-C(O)-R′] derived from the glycosamine N-acetyl functions. Decomposition of these species by transition metal ions gives polymer-derived amidyl (nitrogen-centred) radicals [R-N•-C(O)-R′], polymer-derived carbon-centred radicals and site-specific strand scission. In the present study, we have shown that exposure of glycosaminoglycan chloramides to O2•− also promotes chloramide decomposition and glycosaminoglycan fragmentation. These processes are inhibited by superoxide dismutase, metal ion chelators and the metal ion-binding protein BSA, consistent with chloramide decomposition and polymer fragmentation occurring via O2•−-dependent one-electron reduction, possibly catalysed by trace metal ions. Polymer fragmentation induced by O2•− [generated by the superoxide thermal source 1, di-(4-carboxybenzyl)hyponitrite] was demonstrated to be entirely chloramide dependent as no fragmentation occurred with the native polymers or when the chloramides were quenched by prior treatment with methionine. EPR spin-trapping experiments using 5,5-dimethyl1-pyrroline-N-oxide and 2-methyl-2-nitrosopropane have provided evidence for both O2•− and polymer-derived carbon-centred radicals as intermediates. The results obtained are consistent with a mechanism involving one-electron reduction of the chloramides to yield polymer-derived amidyl radicals, which subsequently undergo intramolecular hydrogen atom abstraction reactions to give carbon-centred radicals. The latter undergo fragmentation reactions in a site-specific manner. This synergistic damage to glycosaminoglycans induced by HOCl and O2•− may be of significance at sites of inflammation where both oxidants are generated concurrently.

Self assembly of a tren-derivative hydrogenated Schiff base with transition metal ions: syntheses, crystal structures and photoluminescent properties

CrystEngComm ◽  
2012 ◽  
Vol 14 (8) ◽  
pp. 2879 ◽  
Author(s):  
Yuehong Wen ◽  
Tianlu Sheng ◽  
Qilong Zhu ◽  
Shengmin Hu ◽  
Chunhong Tan ◽  
...  
Keyword(s):  
Schiff Base ◽  
Transition Metal ◽  
Metal Ions ◽  
Crystal Structures ◽  
Self Assembly ◽  
Transition Metal Ions

scholarly journals Coordination chemistry of glutathione.

1999 ◽  
Vol 46 (3) ◽  
pp. 567-580 ◽  
Author(s):  
A Krezel ◽  
W Bal
Keyword(s):  
Glutamic Acid ◽  
Metal Ions ◽  
Metal Ion ◽  
Reduced Glutathione ◽  
Transition Metal Ions ◽  
Oxidized Glutathione ◽  
Binding Modes ◽  
Glutamic Acid Residue ◽  
Reduced And Oxidized Glutathione ◽  
Soft Metal

The metal ion coordination abilities of reduced and oxidized glutathione are reviewed. Reduced glutathione (GSH) is a very versatile ligand, forming stable complexes with both hard and soft metal ions. Several general binding modes of GSH are described. Soft metal ions coordinate exclusively or primarily through thiol sulfur. Hard ones prefer the amino acid-like moiety of the glutamic acid residue. Several transition metal ions can additionally coordinate to the peptide nitrogen of the gamma-Glu-Cys bond. Oxidized glutathione lacks the thiol function. Nevertheless, it proves to be a surprisingly efficient ligand for a range of metal ions, coordinating them primarily through the donors of the glutamic acid residue.

scholarly journals The Role of Metals in the Reaction Catalyzed by Metal-Ion-Independent Bacillary RNase

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Yulia Sokurenko ◽  
Vera Ulyanova ◽  
Pavel Zelenikhin ◽  
Alexey Kolpakov ◽  
Dmitriy Blokhin ◽  
...  
Keyword(s):  
Metal Ions ◽  
Rna Structure ◽  
Metal Ion ◽  
Extracellular Enzymes ◽  
Bacillus Pumilus ◽  
Transition Metal Ions ◽  
The Body ◽  
Intestinal Microbiome ◽  
Phosphodiester Bond

Extracellular enzymes of intestinal microbiota are the key agents that affect functional activity of the body as they directly interact with epithelial and immune cells. Several species of theBacillusgenus, likeBacillus pumilus, a common producer of extracellular RNase binase, can populate the intestinal microbiome as a colonizing organism. Without involving metal ions as cofactors, binase depolymerizes RNA by cleaving the 3′,5′-phosphodiester bond and generates 2′,3′-cyclic guanosine phosphates in the first stage of a catalytic reaction. Maintained in the reaction mixture for more than one hour, such messengers can affect the human intestinal microflora and the human body. In the present study, we found that the rate of 2′,3′-cGMP was growing in the presence of transition metals that stabilized the RNA structure. At the same time, transition metal ions only marginally reduced the amount of 2′,3′-cGMP, blocking binase recognition sites of guanine at N7 of nucleophilic purine bases.

2,2î-Bipyridine Catalyzed Bleaching of Cotton Fibers with Peracetic Acid

1988 ◽  
Vol 58 (4) ◽  
pp. 198-210 ◽  
Author(s):  
James W. Rucker ◽  
David M. Cates
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Peracetic Acid ◽  
Metal Ion ◽  
Solution Treatment ◽  
Transition Metal Ions ◽  
Ferrous Ion ◽  
Cotton Fibers ◽  
Lauryl Sulfate ◽  
Ferrous Ions

Peracetic acid can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating 2,2î-bipyridine in the bleach solution. Treatment of the fibers with HCl prior to bleaching reduces bleaching effectiveness by removing trace transition metal ions from the fibers. Sorption of individual ions (Cr+3 Mn+2, Fe+2, Fe+3 Co+2, Ni+2, Cu+2, and Zn+2) by HCl treated cotton fibers prior to bleaching indicates that the ferrous ion produces the greatest catalytic effect, and it is only effective when the metal ion is in the fiber as opposed to in solution. Ferrous ions in the fibers sorb 2,2î-bipyridine from solution to form the tris-2,2î-bipyridine ferrous ion complex that is associated with the fibers, and it is the trischelate associated with the fibers that catalyzes bleaching. The effects of pH, temperature, and concentrations of 2,2î-bipyridine, sodium lauryl sulfate, and transition metal ions (in the fibers and in solution) on bleaching effectiveness and peracetic acid decomposition have been studied, and a bleaching mechanism is proposed.

Adsorption of Cu2+ Metal Ions on Dithizone-Immobilized Natural Bentonite

2020 ◽  
Vol 840 ◽  
pp. 64-70
Author(s):  
Dian Mira Fadela ◽  
Mudasir Mudasir ◽  
Adhitasari Suratman
Keyword(s):  
Adsorption Isotherm ◽  
Complex Formation ◽  
Metal Ions ◽  
Electrostatic Interaction ◽  
Metal Ion ◽  
Synthesis And Characterization ◽  
Optimum Conditions ◽  
Initial Concentration ◽  
Activated Bentonite

The research of adsorption of Cu2+ metal ion on dithizone-immobilized natural bentonite (DNB) had been carried out. The experiment was begun by the activation of natural bentonite with HCl 4 M and dithizone-immobilized on activated bentonite surface. This study included synthesis and characterization of dithizone-immobilized bentonite and its application in adsorption of Cu2+ metal ions. The type of interaction occurred in the adsorption was tested by sequential desorption. The result showed that dithizone successfully immobilized on activated natural bentonite (ANB). The optimum conditions for Cu2+ metal ions adsorption using dithizone-immobilized natural bentonite are at pH 5; 0.1 g mass of adsorbent, with interaction time 60 min, and the initial concentration of ion at 80 ppm. Kinetics and adsorption isotherm studies suggest that the capacity, of the dithizone-immobilized natural bentonite in adsorbing Cu2+ metal ion is significantly improved compared to activated natural bentonite. The adsorption of Cu2+ metal ions by activated natural bentonite was through several interactions dominated by electrostatic interaction (82%). Otherwise, the interaction of dithizone-immobilized natural bentonite with Cu2+ metal ions in the sequence were dominated by the mechanism of complex formation of (75%). The result shows that the immobilization of dithizone changes the type of electrostatic interaction into complex formation.

scholarly journals Copper Complexing Capacity and Trace Metal Content in Common and Balsamic Vinegars: Impact of Organic Matter

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 861
Author(s):  
Sotirios Karavoltsos ◽  
Aikaterini Sakellari ◽  
Vassilia J. Sinanoglou ◽  
Panagiotis Zoumpoulakis ◽  
Marta Plavšić ◽  
...  
Keyword(s):  
Organic Matter ◽  
Metal Ions ◽  
Metal Ion ◽  
Metal Speciation ◽  
Anodic Stripping Voltammetry ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Transition Metal Ions ◽  
Electrochemical Technique ◽  
Mass Unit

Complex formation is among the mechanisms affecting metal bioaccessibility. Hence, the quantification of organic metal complexation in food items is of interest. Organic ligands in solutions of environmental and/or food origin function as buffering agents against small changes in dissolved metal concentrations, being able to maintain free metal ion concentrations below the toxicity threshold. Organic matter in vinegars consists of bioactive compounds, such as polyphenols, Maillard reaction endproducts, etc., capable of complexing metal ions. Furthermore, transition metal ions are considered as micronutrients essential for living organisms exerting a crucial role in metabolic processes. In this study, differential pulse anodic stripping voltammetry (DPASV), a sensitive electrochemical technique considered to be a powerful tool for the study of metal speciation, was applied for the first time in vinegar samples. The concentrations of Cu complexing ligands (LT) in 43 vinegars retailed in Greece varied between 0.05 and 52 μM, with the highest median concentration determined in balsamic vinegars (14 μM), compared to that of common vinegars (0.86 μM). In 21% of the vinegar samples examined, LT values were exceeded by the corresponding total Cu concentrations, indicating the presence of free Cu ion and/or bound within labile inorganic/organic complexes. Red grape balsamic vinegars exhibited the highest density of Cu ligands per mass unit of organic matter compared to other foodstuffs such as herbal infusions, coffee brews, and beers. Among the 16 metals determined in vinegars, Pb is of particular importance from a toxicological point of view, whereas further investigation is required regarding potential Rb biomagnification.

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