Metal chelates of ampicillin versus amoxicillin: synthesis,structural investigation,and biological studies

Solid chelates derived from some alkaline earth and transition metal complexes with ampicillin (Hamp, a) and amoxicillin (Hamox, b) were synthesized and characterized using elemental analysis, molar conductivity, IR, magnetic susceptibility, and thermogravimetric studies. Both drugs behave as tetradentate ligands coordinating to metal through amino, imino, and carboxylate as well as through β-lactamic carbonyl. All chelates have octahedral geometry except Cu(II) complexes which have square planar structure and uranium has pentagonal bipyramidal coordination. ¹H- and ¹³C-NMR of the Zn(II) and UO₂(VI) chelates are compared with the free ligands. The antimicrobial activity of the prepared chelates was determined.     

Thin-Layer Chromatographic Separation of Copper and Mercury Chelates

Abstract

Thin-layer chromatographic separation of metal ions has become immensely popular in analytical chemistry in view of its speed, selectivity and applicability at tracer level. Quinoline-2-aldehyde thiosemicarbazone^1,2 was found to form yellow coloured chelates with metal ions such as copper, nickel, zinc, mercury, iron and lead at pH 7.5 and extract into chloroform. This, however reduces the sensitivity of the reagent as a chromogenic agent but the chromatographic run of the chelates on a thin layer of silica gel coated on glass plate increases the specificity and selectivity of the reagent. In this article we propose a method for separation of copper and mercury chelates from binary mixtures containing chelates of zinc, lead, iron and nickel. The method is applicable for analysis of synthetic mixtures and standard samples.     

Jones-Dole Equation B Coefficients for Metal Chelates and Selected Ligands

Abstract

The B coefficient of the Jones-Dole equation is required to determine the size of the solvation sphere of a molecule in solution. Those obtained for metal chelates and selected ligands are presented.     

Ligand Exchange Reactions for the Fluorescent Detection of Nanogram Amounts of Metal Ions on TLC Plates

Abstract

A number of metal ions have been separated as their diethyldithiocarbamate chelates by thin-layer chromatography and detected by means of a ligand exchange reaction between a metal/calcein complex and the diethyldithiocarbamate chelate. Visual detection limits, after development, are 0.1 to 2 ng per spot for the metal ions studied. The potential of this new method for the fluorescent analysis of metal ions is discussed. It is particularly promising as a simple field method. Spiked natural water samples are analyzed to demonstrate its usefulness.     

A Solution‐based Method for Synthesizing Pyrite‐type Ferrous Metal Sulfide Microspheres with Efficient OER Activity

Simple and stable synthesis of transition metal sulfides and clarification of their growth mechanisms are of great importance for developing catalysts, metal‐air batteries and other technologies. In this work, we developed a one‐step facile hydrothermal approach to successfully synthesize NiS₂ microspheres. By changing the experimental parameters, the reason that affects the formation of nanostructured spheres is investigated and discussed in detail, and the formation mechanism of microspheres is proposed innovatively. Furthermore, electrochemical testing results show that the 7 h‐NiS₂ catalyst exhibits a remarkable oxygen evolution reaction (OER) activity with an overpotential of 311 mV at 10 mA cm^?2 in 1.0 M KOH, superior to precious metal RuO₂. The NiS₂ catalyst also exhibits a robust durability. This work will contributes to the rational design and the understanding of growth mechanism of transition metal chalcogenide electrocatalysts for diverse energy conversion technologies.     

Solid-state chemistry on a surface and in a beaker: Unconventional routes to transition metal chalcogenide nanomaterials

This article focuses on two different approaches to create nanoscale transition metal chalcogenide materials. First, we used chemical nanofabrication, a combination of top-down patterning and bottom-up solid-state synthesis, to achieve control over the shape, size, and ordering of the patterned nanomaterials. We demonstrated orientational control over nanocrystals within sub-300 nm patterns of MoS₂ and formed free-standing nanostructures of crystalline NiS₂. In addition, crossed line arrays of mixed metal chalcogenide nanostructures were achieved, and TaS₂ nanopatterns were made by the chemical transformation of tantalum oxide templates. Second, we developed a one-pot procedure using molecular precursors to synthesize two-dimensional NbSe₂, TaS₂ and TaSe₂ nanoplates and one-dimensional NbSe₂ wires depending on the relative amount of surfactants in the reaction mixture. Prospects for these transition metal chalcogenide nanomaterials with controlled shapes and morphologies will be discussed.     

Engineering strength, porosity, and emission intensity of nanostructured CdSe networks by altering the building-block shape

The effect of primary particle shape on the porosity, mechanical strength, and luminescence intensity of metal chalcogenide aerogels was probed by comparison of CdSe aerogels prepared from spherical and rod-shaped particles. Rod-shaped particles yield aerogels with polymeric morphologies in contrast to the colloidal morphology obtained from spherical particles. Relative to the colloidal analogues, the polymeric CdSe aerogels exhibit twice the surface area, a doubling of the complex viscosity for 5 wt % aerogel-PDMS composites, and a 25-fold increase in emission intensity. Altering the shape of the building block from which nanostructured networks are assembled is an effective way to tune the basic properties of metal chalcogenide semiconducting aerogels.     

Spectrometry: Speciation of Parts PER Billion of Metal Ions Using Silica and C18-Bonded Silica Columns and Graphite Furnace Atomic Absorption Spectrometry

Abstract

It is demonstrated that silica gel columns will quantitatively adsorb free Cu²⁺ and Pb²⁺ ions at pH > 8. These are eluted with 0.1 M HNO₃ but not with methanol. Negatively charged EDTA chelates are not adsorbed. Neutral APDC chelates are partially adsorbed on silica columns, but are quantitatively adsorbed on C18-bonded columns, and are eluted with methanol. The metal ions are partially adsorbed on C18-bonded columns, due to residual silanol groups. A microcolumn (1 mm i.d., 5 cm length) manifold system is described for automatic delivery of eluant (0.12 ml) to a heated atomic absorption graphite atomizer, using either methanol or 0.1 M HNO₃ in methanol eluant, allowing speciation and measurement of parts per billion of metals. These studies demonstrate that by using a mixed column or sequential columns of silica gel and C18-bonded silica, cationic and neutral metal species could be adsorbed, followed by sequential elution and measurement using methanol and then 0.1 M HNO. Negatively charged species could be measured directly in the sample eluant or obtained by difference from a total metal measurement.     

An Improved Instrument for Measuring the Ultrasonic Absorption of Metal Chelate Adducts

Abstract

The purpose of this instrument is to provide a means to measure the rates of exchange, ΔG, ΔS, and ΔH of water and organic solvent adducts on metal chelates.

The instrument employs a pulsed ultrasonic technique which perturbs the equilibrium of a metal chelate and then measures the rate at which it returns to equilibrium.

This instrument is 10 times more sensitive than a previous instrument and was tested by examining the vanadium(V) benzo-hydroxamic acid chelate in n-butanol.     

Determination of Copper,Cadmium and Lead in Zinc Metal by Preconcentration onto Activated Carbon Combined with Direct Current Arc Atomic Emission Spectrography

Abstract

A preconcentration method is described for traces of copper, cadmium and lead from pure zinc metal by use of activated carbon. Ammonium salt of dithiophosphoric acid-o, o-diethylester is used to complex Cu, Cd and Pb. These chelates are sorbed on activated carbon. The traces sorbed on the carbon are determined by direct current arc atomic emission spectrography. The analytical error in the concentration range of 10^?3–10^?4% is less than 6% and relative standard deviation is below 10%.     

Review: Metal Complexes as Ligands

Ligand properties of coordination and organometallic compounds are examined on the basis of acid-base interactions of metal-containing bases and Lewis acids. Such interactions lead to homo- or heteronuclear di- and polynuclear complexes. Special attention is given to coordinatively-unsaturated molecules of classic Werner complexes, o -hydroxyazomethine chelates, metal carbonyls and their derivatives, ferrocenes with donor fragments, and coordinated heteroaromatic compounds.     

COMPLEXES OF GALLIUM(III) WITH HYDROXYAROMATIC LIGANDS

Abstract

The equilibria between gallium(III) ion and selected hydroxyaromatic and dihydroxyaromatic ligands at 25°C, μ=0.100 M (KNO₃) have been determined. Potentiometric measurements on 1:1, 2:1, and 3:1 molar ratios of ligand to Ga(III) have been made as a function of degree of neutralization over the entire accessible ?log [H⁺] scale. Calculations were carried out so as to take account of competing hydrolytic reactions, and formation constants of gallium(III) with chromotropic acid, 8-hydroxyquinoline-5-sulfonic acid, 5-sulfosalicylic acid, and 1,2-dihydroxy-benzene-3,5-disulfonic acid were obtained. Stable hydroxo chelates do not form under the reaction conditions employed. The protonation constants of the ligands and the formation constants of the gallium chelates are discussed and compared with previously published work on these gallium chelates and on chelates of “analogous” metal ions such as those of Fe(III) and A1(III).     

Biomedical Implications of Polyphosphates

Abstract

The polyphosphates have the capacity of forming chelates with most of that metal cations[l]. Polyphosphatic complexes with trace- and macroelements art used as fodder additives for animals. In our experiments we studied the effect 01pyrophosphate (PP), tripolyphosphate (TPP) and hexametaphosphate (HMP), at different concentrations (0.909 mM, 1.8 I8 mM and 2.727 mM), on the enzymatic activity of carbonic anhydrase (CA), and the effect of polyphosphate chelates or the enzymatic activity of alkaline phosphatase (AP), both zincenzymes. The meta; ion, which can be dissociated in the presence of a chelating agent, is essential foi their catalytic activity 121. The presence of metal atoms as essential constituents of some enzymes, and the metal requirements of others for maximum activity, provide an obvious link between enzymatic reaction and coordination chemistry.     

Water and Organic Solvent Adducts on Metal Chelates

Abstract

The number of water and organic solvent molecule adducts surrounding several ligands and metal chelates were determined in both the aqueous and organic phases. Data is presented to show that these adducts change in number during an extraction.     

Incorporation of transition metals into Mg-Al layered double hydroxides: Coprecipitation of cations vs. their pre-complexation with an anionic chelator

A comparative study on two different methods for preparing Mg-Al layered double hydroxides (LDH) containing various divalent transition metals M (M=Co, Ni, Cu) has been carried out. The first (conventional) method involved coprecipitation of divalent metals M(II) with Mg(II) and Al(III) cations using carbonate under basic conditions. The second approach was based on the ability of transition metals to form stable anionic chelates with edta⁴⁻ (edta⁴⁻=ethylenediaminetetraacetate) that were synthesized and further introduced into LDH by coprecipitation with Mg and Al. The synthesized LDHs were characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF) methods, thermogravimetry with mass-selective detection of decomposition products (TG-MSD), Fourier transform infrared (FTIR) and Raman spectroscopy techniques. The results obtained were discussed in terms of efficiency of transition metal incorporation into the LDH structure, thermal stability of materials and the ability of metal chelates to intercalate the interlayer space of Mg-Al LDH. Vibrational spectroscopy studies confirmed that the integrity of the metal chelates was preserved upon incorporation into the LDH.     

SYNTHESIS OF 5-DODECANOYLAMINE-8-HYDROXY-1,4-NAPHTHOQUINONE AND STUDY OF SOME OF ITS BIVALENT METAL CHELATES

Abstract

Two new naphthoquinone derivatives, 5-dodecanoylamine-8-hydroxy-l,4-naphthoquinone (1) and 5-dodecanoylamine-8-acetoxy-l,4-naphthoquinone (2), have been prepared and characterized. Their chelating ability with Ni(II) and Co(II) have been studied. Compound (1) coordinates to the divalent metal ions as a monoanionic bidentate ligand. The complexes were found to contain two ligands and two molecules of coordinated water. The structure and bonding of the chelates are discussed based on the spectroscopic data.     

Vapor-Liquid Equilibrators To Aid In Making Measurements To Determine Solvent Adducts On Metal Chelates

Abstract

Two vapor-liquid equilibrators to saturate water with organic solvent without forming two liquid phases were developed, thus permitting a more accurate determination of organic adducts to metal chelates. An equation was developed to show that vapor pressure measurements could be used as an alternative method for determining the number of organic adducts on a metal chelate in the aqueous phase.     

Crystal Structures of DOTMA Chelates from Ce3+ to Yb3+: Evidence for a Continuum of Metal Ion Hydration States

The crystal structures of chelates formed between each stable paramagnetic lanthanide ion and the octadentate polyamino carboxylate ligand DOTMA are described. A total of 23 individual chelates structures were obtained; in each chelate the coordination geometry around the metal ion is best described as a twisted square antiprism (torsion angle −25.0°–−31.4°). Despite the uniformity of the general coordination geometry provided by the DOTMA ligand, there is a considerable variation in the hydration state of each chelate. The early Ln³⁺ chelates are associated with a single inner sphere water molecule; the Ln-OH₂ interaction is remarkable for being very long. After a clear break at gadolinium, the number of chelates in the unit cell that have a water molecule interacting with the Ln³⁺ decreases linearly until at Tm³⁺ no water is found to interact with the metal ion. The Ln-OH₂ distance observed in the chelates of the later Ln³⁺ ions are also extremely long and increase as the ions contract (2.550–2.732 Å). No clear break between hydrated and dehydrated chelates is observed; rather this series of chelates appear to represent a continuum of hydration states in which the ligand gradually closes around the metal ion as its ionic radius decreases (with decreased hydration) and the metal drops down into the coordination cage.     

Gel Chromatography of Metal Acetylacetonates in Organic Solvents

Abstract

Tris (acetylacetonato)cobalt(III) and tris(acetylacetonato)-chromium(III) have been eluted by gel chromatography through styrene-divinylbenzene copolymer gel using an organic solvent as an eluent. Elution counts of these chelates in these solvents reflect some mutual interactions between metal chelate, gel and solvent. When benzene or chloroform was used as an eluent, sieving effect seems to be dominant for the separation of these chelates. Discussions were done in relation to solubility parameters of the solvent, the complex and the gel.     

Graphene‐Assisted Room‐Temperature Synthesis of 2D Nanostructured Hybrid Electrode Materials: Dramatic Acceleration of the Formation Rate of 2D Metal Oxide Nanoplates Induced by Reduced Graphene Oxide Nanosheets

A new prompt room temperature synthetic route to 2D nanostructured metal oxide–graphene‐hybrid electrode materials can be developed by the application of colloidal reduced graphene oxide (RGO) nanosheets as an efficient reaction accelerator for the synthesis of δ‐MnO₂ 2D nanoplates. Whereas the synthesis of the 2D nanostructured δ‐MnO₂ at room temperature requires treating divalent manganese compounds with persulfate ions for at least 24 h, the addition of RGO nanosheet causes a dramatic shortening of synthesis time to 1 h, underscoring its effectiveness for the promotion of the formation of 2D nanostructured metal oxide. To the best of our knowledge, this is the first example of the accelerated synthesis of 2D nanostructured hybrid material induced by the RGO nanosheets. The observed acceleration of nanoplate formation upon the addition of RGO nanosheets is attributable to the enhancement of the oxidizing power of persulfate ions, the increase of the solubility of precursor MnCO₃, and the promoted crystal growth of δ‐MnO₂ 2D nanoplates. The resulting hybridization between RGO nanosheets and δ‐MnO₂ nanoplates is quite powerful not only in increasing the surface area of manganese oxide nanoplate but also in enhancing its electrochemical activity. Of prime importance is that the present δ‐MnO₂–RGO nanocomposites show much superior electrode performance over most of 2D nanostructured manganate systems including a similar porous assembly of RGO and layered MnO₂ nanosheets. This result underscores that the present RGO‐assisted solution‐based synthesis can provide a prompt and scalable method to produce nanostructured hybrid electrode materials.