Effects of substituent groups and central metal ion on hydrogen adsorption in zeolitic imidazolate frameworks

2013 ◽  
Vol 97 ◽  
pp. 60-66 ◽  
Author(s):  
Er-Yu Chen ◽  
Ying-Chun Liu ◽  
Tian-Yang Sun ◽  
Qi Wang ◽  
Li-Jun Liang
Keyword(s):  
Metal Ion ◽  
Hydrogen Adsorption ◽  
Central Metal ◽  
Zeolitic Imidazolate Frameworks

Protonation effects on dynamic flux properties of aqueous metal complexes

2009 ◽  
Vol 74 (10) ◽  
pp. 1543-1557 ◽  
Author(s):  
Herman P. Van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Complex Formation ◽  
Metal Ion ◽  
Good Description ◽  
Minor Component ◽  
Outer Sphere ◽  
Metal Species ◽  
Central Metal ◽  
Inner Sphere ◽  
A Minor ◽  
Protonated Ligand

The degree of (de)protonation of aqueous metal species has significant consequences for the kinetics of complex formation/dissociation. All protonated forms of both the ligand and the hydrated central metal ion contribute to the rate of complex formation to an extent weighted by the pertaining outer-sphere stabilities. Likewise, the lifetime of the uncomplexed metal is determined by all the various protonated ligand species. Therefore, the interfacial reaction layer thickness, μ, and the ensuing kinetic flux, Jkin, are more involved than in the conventional case. All inner-sphere complexes contribute to the overall rate of dissociation, as weighted by their respective rate constants for dissociation, kd. The presence of inner-sphere deprotonated H2O, or of outer-sphere protonated ligand, generally has a great impact on kd of the inner-sphere complex. Consequently, the overall flux can be dominated by a species that is a minor component of the bulk speciation. The concepts are shown to provide a good description of experimental stripping chronopotentiometric data for several protonated metal–ligand systems.

MetLigDB: a web-based database for the identification of chemical groups to design metalloprotein inhibitors

2011 ◽  
Vol 44 (4) ◽  
pp. 878-881 ◽  
Author(s):  
Hwanho Choi ◽  
Hongsuk Kang ◽  
Hwangseo Park
Keyword(s):  
Drug Discovery ◽  
Metal Ions ◽  
Metal Ion ◽  
Central Metal ◽  
Amino Acid Residues ◽  
Web Based ◽  
Additional Information ◽  
Chemical Groups ◽  
Insight Into ◽  
Chelating Groups

MetLigDB (http://silver.sejong.ac.kr/MetLigDB) is a publicly accessible web-based database through which the interactions between a variety of chelating groups and various central metal ions in the active site of metalloproteins can be explored in detail. Additional information can also be retrieved, including protein and inhibitor names, the amino acid residues coordinated to the central metal ion, and the binding affinity of the inhibitor for the target metalloprotein. Although many metalloproteins have been considered promising targets for drug discovery, it is difficult to discover new inhibitors because of the difficulty in designing a suitable chelating moiety to impair the catalytic activity of the central metal ion. Because both common and specific chelating groups can be identified for varying metal ions and the associated coordination environments, MetLigDB is expected to give users insight into designing new inhibitors of metalloproteins for drug discovery.

scholarly journals Synthesis, characterization and antibacterial activity of metalloporphyrins: Role of central metal ion

2020 ◽  
Vol 2 ◽  
pp. 100073
Author(s):  
Belete B. Beyene ◽  
Ayenew M. Mihirteu ◽  
Misganaw T. Ayana ◽  
Amogne W. Yibeltal
Keyword(s):  
Antibacterial Activity ◽  
Metal Ion ◽  
Central Metal

On the Kinetics and Mechanism of Spontaneous Intramolecular Reduction of the Central Metal Ion in K2[Mn(IV)-2-α-hydroxyethyl isochlorin e4] Acetate in Aqueous Alkaline Solutions and its Relation to the Binding Sites of Manganese in Photosynthesis

1975 ◽  
Vol 30 (5-6) ◽  
pp. 327-332 ◽  
Author(s):  
Gerhard Vierke ◽  
Manfred Müller
Keyword(s):  
Electron Transfer ◽  
Metal Ion ◽  
Reaction Rates ◽  
Bimolecular Reaction ◽  
Reduction Reaction ◽  
Alkaline Solutions ◽  
Central Metal ◽  
Pseudo First Order Reaction ◽  
Spontaneous Reduction ◽  
Acid Base Equilibrium

Abstract Spectrophotometric investigation of the kinetics of the spontaneous reduction of the central metal ion in K2[Mn (IV)-2-α-hydroxyethyl-isochlorine e4] acetate in aqueous alkaline solution in the absence of any reducing agent reveals that it is a pseudo-first order reaction which is specifically hydroxide ion catalyzed. The pKα-value of the acid-base equilibrium has been estimated to be 14.4. Electron transfer to the central metal ion is the rate limiting step. The measurements of its temperature dependence yields an activation enthalpy of ∆H‡ = 12 kcal/mol and an entropy of activation ∆S‡ = - 30 e.u. thus indicating that the electron transfer step is a bimolecular reaction. The most likely reactant is water. The reduction reaction does not take place with appreciable reaction rates at physiological pH. Thus, when bound to a suitable ligand of the chlorin type, Mn (IV)-compounds are sufficiently stable with respect to autoxidation to play some role in biological redox reactions as postulated recently for the photoreactivation process of the water splitting system in photosynthesis.

scholarly journals SYNTHESIS, MOLLUSCICIDALAND ANTIMICROBIAL POTENTIALITIES OF IRON TRIAD MONONUCLEAR METAL COMPLEXES INCORPORATING TRIDENTATE ASYMMETRICAL SCHIFF BASE LIGANDS CONTAINING SOFT SULFUR COORDINATING ATOM

2019 ◽  
pp. 103-113
Author(s):  
AMAL M ALOSAIMI ◽  
INES EL MANNOUBI ◽  
SAMI A ZABIN
Keyword(s):  
Schiff Base ◽  
Metal Complexes ◽  
Metal Ion ◽  
Lethal Dose ◽  
Analytical Techniques ◽  
Central Metal ◽  
Schiff Base Ligands ◽  
Molluscicidal Activity

Objective: This work aimed at synthesizing tridentates asymmetrical Schiff base ligands containing sulfur atom and using them for preparing metal complexes with the iron triad metals. The prepared compounds were assayed in vitro for antimicrobial potential and in vivo molluscicidal activity. Methods: The unsymmetrical tridentate Schiff bases (SL1, SL2, and SL3) were prepared using 2-aminothiophenol as primary amine and condensed with 2-carboxybenzaldehyde, 2-hydroxy-1-naphthaldehyde, and 7-formyl-8-hydroxyquinoline. These ligands were used in preparing metal complexes with iron triad metals. The synthesized Schiff base ligands and their corresponding metal complexes were characterized and their proposed structures were confirmed using different physical and spectroscopic analytical techniques. All ligands and their corresponding metal complexes were assayed against different bacterial and fungal strains using the agar disk-diffusion technique. The molluscicidal activity was performed according to the standard reported methods as cited in the literature and by observing the toxicity and lethal dose according to the WHO guidelines. Results: The synthesized ligands behave as tridentate (NOS) ligands and form mononuclear complexes with the general formula [M(SL)2] with an octahedral geometry around the central metal ion. Metal complexes were non-electrolytic in nature. The in vitro antibacterial and antifungal examination results showed weak activity of the ligands, and there was enhanced activity with the complexes. The in vivo molluscicidal activity of the tested compounds showed good activity. Conclusion: The targeted compounds were prepared successfully, characterized, and showed some biological activity but lower than the standard reference drugs.

THE EFFECT OF BETA-DECAY ON THE EXCHANGE PROPERTIES OF THE RARE EARTH–EDTA COMPLEX IONS

1961 ◽  
Vol 39 (5) ◽  
pp. 1049-1053 ◽  
Author(s):  
P. Glentworth ◽  
R. H. Betts
Keyword(s):  
Rare Earth ◽  
Metal Ion ◽  
Chemical Reactivity ◽  
Sudden Change ◽  
Chelating Agent ◽  
Beta Particle ◽  
Central Metal ◽  
Complex Ions ◽  
Rare Earth Ion ◽  
The Rare Earth

It is shown that the rare earth ion Yb3+ is very resistant towards ordinary thermal exchange when it is complexed with the chelating agent EDTA in aqueous solution. However, when the complexed rare earth atom, as the 1.8-h Yb-177, emits a beta-particle, the daughter atom Lu-177 escapes readily from the chelate structure. Nuclear recoil arising from the beta-particle emission is shown not to be the cause of the escape of the daughter atom. It is suggested that the observed lability of the daughter atom is a result of a high degree of chemical reactivity of the chelate ion arising from the sudden change in atomic number of the central metal ion of the chelate structure.

Preparation and Luminescent Properties of the La3+ Doped Tb3+-Hydroxyapatite

2014 ◽  
Vol 716-717 ◽  
pp. 32-35
Author(s):  
Wen Bin Liu ◽  
Adu ◽  
Yu Guang Lv ◽  
Li Li Yu ◽  
Yong Xiang Du ◽  
...  
Keyword(s):  
Rare Earth ◽  
Metal Ion ◽  
Chemical Properties ◽  
Earth Metal ◽  
Luminescent Properties ◽  
Central Metal ◽  
X Ray Diffraction ◽  
Light Emitting ◽  
Terbium Ion ◽  
The Stability

In this paper, a rare earth metal terbium ion as the central metal ion, a nanohydroxyapatite powder of the lanthanum doped terbium was synthesis by precipitation with hydroxyapatite as ligand. The sample was characterized by infrared spectrum, fluorescence spectrum and X ray diffraction instrument, and the thermal properties and fluorescence properties, structure of powderes were discussed. A nanohydroxyapatite powder of the lanthanum doped terbium achieves the maximum luminous intensity, when the La3+ doping concentration of Tb3+ was HAP 5% (La3+ and Tb3+ mole fraction ratio) devices. Rare earth powder of the lanthanum doped terbium hydroxyapatite has the stability chemical properties, the luminescence properties and good biological activity, the rare earth powder has good luminescent properties can be used in preparation of a good light emitting device. At the same time a nanohydroxyapatite powder of the lanthanum doped terbium has good antibacterial property, can be used as antibacterial materials.

Metal-Mediated Pseudo Coordination Isomerism in Complexes of Mixed Neutral Didentate and Dianionic Tridentate Pyridine-Containing Ligands

2004 ◽  
Vol 57 (6) ◽  
pp. 565 ◽  
Author(s):  
Nathaniel W. Alcock ◽  
Guy J. Clarkson ◽  
Geoffrey A. Lawrance ◽  
Peter Moore
Keyword(s):  
Hydrogen Bonding ◽  
Metal Ion ◽  
Mixed Ligand Complex ◽  
Molar Ratio ◽  
High Yield ◽  
Axial Position ◽  
Water Molecules ◽  
Central Metal ◽  
Ligand Complex ◽  
Space Group

Reaction of nickel(II) or copper(II) acetate with 2-(aminomethyl)pyridine 1 and pyridine-2,6-dicarboxylate ion 2 in aqueous methanol in a 1 : 1 : 1 molar ratio leads to the crystallization in high yield of exclusively one product in each case. For nickel(II), a neutral mixed-ligand complex [Ni · 1 · 2 · (OH2)] is obtained, whereas with copper(II) an ionic complex [Cu · 12 · (OHCH3)][Cu · 22] forms wherein each complex ion contains exclusively one type of ligand. The outcome appears to be directed by the metal ion employed, the two forms being effectively coordination isomers, albeit differing in central metal ion. The neutral complex [Ni · 1 · 2 · (OH2)] · 4¼H2O crystallizes in the triclinic space group P¯1, with two independent nickel centres and ten (some with partial occupancy) water molecules in the asymmetric unit. Each nickel lies in a distorted octahedral environment, with the three N-donor and O-donor sets occupying meridional positions. A complex system of hydrogen bonding and Π-stacking operates in the crystal, with arrays of complex units arranged in ‘dimer tapes’ surrounded by water molecules. The ionic [Cu · 12 · (OHCH3)][Cu · 22] · 2CH3OH complex crystallizes in the monoclinic P21/c space group. The cation adopts a distorted square-based pyramidal geometry with a coordinated methanol in the axial position, although another is weakly interacting in the other axial site. The anion exists in the previously described octahedral geometry with two meridionally-disposed tridentate ligands with the pyridines disposed in trans positions. Three-dimensional ordering in the structure is directed by ‘ribbons’ of hydrogen bonding.

scholarly journals Synthesis, Spectroscopic, and Antimicrobial Studies on Bivalent Nickel and Copper Complexes of Bis(thiosemicrbazone)

2007 ◽  
Vol 2007 ◽  
pp. 1-7 ◽  
Author(s):  
Sulekh Chandra ◽  
Smriti Raizada ◽  
Monika Tyagi ◽  
Archana Gautam
Keyword(s):  
Metal Complexes ◽  
Metal Ion ◽  
Copper Complexes ◽  
Free Ligand ◽  
Antimicrobial Properties ◽  
Molar Conductance ◽  
Spectral Studies ◽  
Central Metal ◽  
Antimicrobial Studies

A series of metal complexes of Cu(II) and Ni(II) having the general composition[M(L)X2]with benzil bis(thiosemicarbazone) has been prepared and characterized by element chemical analysis, molar conductance, magnetic susceptibility measurements, and spectral (electronic, IR, EPR, mass) studies. The IR spectral data suggest the involvement of sulphur and azomethane nitrogen in coordination to the central metal ion. On the basis of spectral studies, an octahedral geometry has been assigned for Ni(II) complexes but a tetragonal geometry for Cu(II) complexes. The free ligand and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties.

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