Polarographic determination of thallium
About: This article is published in Analytica Chimica Acta.The article was published on 1974-02-01. It has received 12 citations till now. The article focuses on the topics: Thallium.
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TL;DR: In this paper, the properties of a novel water soluble thiazolyloxime 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (H3L1) with Cu2+ and Ni2+ were investigated in solution by potentiometrical and spectral (UV-Vis, EPR, NMR) methods.
Abstract: Complex formation properties of a novel water soluble thiazolyloxime 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (H3L1) with Cu2+ and Ni2+ were investigated in solution by potentiometrical and spectral (UV–Vis, EPR, NMR) methods. All Cu2+ and most of Ni2+ complex species detected in solution were found to have square-planar MN4 core with oxime and heterocyclic nitrogen atoms which was rationalized in terms of destabilizing effect of repulsive interaction between oxygen atom of carboxylic group and nitrogen atom of thiazole ring in N,O-coordinated ligand conformation. It has been found that stability of metal complexes in a series of oxime ligands is dependent upon basicity of nitrogen atom of oxime group. The thiazolyloxime forms less stable complexes with Cu2+ but stronger ones with Ni2+ ions when compared to parent 2-(hydroxyimino)propanoic acid. The lower stability obtained for Cu2+ complexes was elucidated in terms of negative inductive effect of the thiazole and nitrile substituents as well as an effect of intramolecular attractive interaction between thiazolyl sulfur and oxime oxygen atoms in thiazolyloxime. In the case of Ni2+ the complexes formed are square-planar and it is why thiazolyl ligand is more effective in metal ion binding than simple 2-(hydroxyimino)propanoic acid forming only octahedral species. The solid state structure of the Co3+ complex K3[Co(HL1)3]·5.5H2O (1) was studied by X-ray analysis. The thiazolyloxime ligand is coordinated to Co3+ via oxime nitrogen and carboxylate oxygen atoms forming five-membered chelate rings.
38 citations
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TL;DR: In this article, the binding ability of oxalodihydroxamic acid (H2oxha) with two hydroxamic groups next to each other differs distinctly from that observed for aliphatic dihydroxamic acids, HONHOC(CH2)nCONHOH (n = 3-8).
Abstract: Solution (potentiometric, absorption, EPR) as well as solid state studies (X-ray, EPR, magnetic susceptibility) have shown that the binding ability of oxalodihydroxamic acid (H2oxha) with two hydroxamic groups next to each other differs distinctly from that observed for aliphatic dihydroxamic acids, HONHOC(CH2)nCONHOH (n = 3–8). H2oxha was found to be a very powerful ligand for NiII and CuII due to an N,N′-chelating binding mode. The availability of the mixed nitrogen–oxygen donor systems results in formation of polymeric complexes with CuII. The crystal structure of K2[Ni(oxha)2]·2H2O has shown two very characteristic features of the dihydroxamic ligand: (i) two short intramolecular hydrogen bonds stabilising very effectively the complex formed and (ii) very specific binding modes of K+ ions, which play a bridging role between [Ni(oxha)2]2− ions. The latter finding demonstrates a capacity of H2oxha-based anionic complex species to form polynuclear complexes with different bridging modes.
35 citations
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TL;DR: In this paper, the crystal structures of two complexes, Na2[NiL2]·4H2O 1 and [Cu(phen)(hpa)(H 2O), were determined by single-crystal X-ray analysis.
Abstract: Potentiometric, spectroscopic and X-ray studies of 2-(hydroxyimino)propanohydroxamic acid (H2L) and its complexes with Ni2+ and Cu2+ showed that the ligand is a strong chelating agent forming a series of stable complex species with remarkably higher formation constants compared to those of either aminohydroxamic acids or oximinocarbonic acids. In the Cu2+–H2L system three dinuclear species [Cu2HL2]+, [Cu2L2] and [Cu2H–1L2]– with different donor atom sets were found to be dominant at pH 3.5–7.5. In both Cu2+ and Ni2+ systems the mononuclear species [MHL2]–, [ML2]2– and [MH–1L2]3– are formed in neutral and alkaline solutions which have, according to the UV-VIS spectral data, square-planar structure with a M{N2(oxime)N2(hydrox)} core. Thus, the ligand studied represents a new example in which the adjacent oxime donor group facilitates the N-bonding of the hydroxamic function. The crystal structures of two complexes, Na2[NiL2]·4H2O 1 and [Cu(phen)(hpa)(H2O)]·4H2O 2 [H2hpa = 2-(hydroxyimino)propanoic acid] have been determined by single-crystal X-ray analysis. In 1 the central atom is situated at the centre of symmetry and in square-planar surroundings of four nitrogen atoms belonging to the deprotonated oxime and hydroxamic groups. The trans-disposed ligands are additionally linked by short intramolecular hydrogen bonds featuring the oxime and hydroxamic oxygen atoms. Complex 2 was crystallised from an alkaline solution containing [Cu(phen)Cl2] and H2L and formed as a result of ligand hydrolysis. The copper(II) ion is in distorted square-pyramidal surrounding, the basal plane being formed by two nitrogen atoms of 1,10-phenanthroline, an oxime nitrogen and a carboxylic oxygen atom of the dianion hpa and the water molecule occupies the apical position. Both organic ligands are co-ordinated in a bidentate chelate mode.
34 citations
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TL;DR: X-ray crystallographic and solution studies have revealed the first examples of complexes of Cu============ 2+672====== and Ni============ 1+672 2+676====== with an oxime======¯¯ derivative in which completely deprotonated ligand molecules bind in======trans position because of the lack of a hydrogen bond between the============hydroxyl oxygens which usually stabilises the cis======positioning.
Abstract: X-Ray crystallographic and solution studies have revealed the first
examples of complexes of Cu
2+
and Ni
2+
with an oxime
derivative in which completely deprotonated ligand molecules bind in
trans position because of the lack of a hydrogen bond between the
hydroxyl oxygens which usually stabilises the cis
positioning.
30 citations
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TL;DR: The βA4 amyloid precursor protein fragment situated in the cysteine-rich region is a very effective binding site for Cu2+ ions due to the presence of three His residues in the His–Xaa–His–Yaa-His sequence.
Abstract: The βA4 amyloid precursor protein fragment situated in the cysteine-rich region is a very effective binding site for Cu2+ ions due to the presence of three His residues in the His–Xaa–His–Yaa–His sequence.
28 citations
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