Stability Of Transition Metal Complexes Research Articles

Homologous acetone carboxylases select Fe(II) or Mn(II) as the catalytic cofactor.

Acetone carboxylases (ACs) catalyze the metal- and ATP-dependent conversion of acetone and bicarbonate to form acetoacetate. Interestingly, two homologous ACs that have been biochemically characterized have been reported to have different metal complements, implicating different metal dependencies in catalysis. ACs from proteobacteria Xanthobacter autotrophicus and Aromatoleum aromaticum share 68% sequence identity but have been proposed to have different catalytic metals. In this work, the two ACs were expressed under the same conditions in Escherichia coli and were subjected to parallel chelation and reconstitution experiments with Mn(II) or Fe(II). Electron paramagnetic and Mössbauer spectroscopies identified signatures, respectively, of Mn(II) or Fe(II) bound at the active site. These experiments showed that the respective ACs, without the assistance of chaperones, second metal sites, or post-translational modifications facilitate correct metal incorporation, and despite the expected thermodynamic preference for Fe(II), each preferred a distinct metal. Catalysis was likewise associated uniquely with the cognate metal, though either could potentially serve the proposed Lewis acidic role. Subtle differences in the protein structure are implicated in serving as a selectivity filter for Mn(II) or Fe(II).IMPORTANCEThe Irving-Williams series refers to the predicted stabilities of transition metal complexes where the observed general stability for divalent first-row transition metal complexes increase across the row. Acetone carboxylases (ACs) use a coordinated divalent metal at their active site in the catalytic conversion of bicarbonate and acetone to form acetoacetate. Highly homologous ACs discriminate among different divalent metals at their active sites such that variations of the enzyme prefer Mn(II) over Fe(II), defying Irving-Williams-predicted behavior. Defining the determinants that promote metal discrimination within the first-row transition metals is of broad fundamental importance in understanding metal-mediated catalysis and metal catalyst design.

The Kinetic of Decolorizing Reactive Orange 122 (RO122) by Peracetic Acid in the Presence of Metal ions and UV Light

Abstract: The kinetic of decolorizing Reactive Orange 122 (RO122) by peracetic acid (PAA) in the presence of metal ionsand UV light at 24 ± 1oChas been studied in this research. All experiments were conducted in a 500 mL reactor in which concentrations of peracetic acid were applied in large excess comparingto reactive orange 122. Four metal ions were tested for catalytic activity including Mn2+, Cu2+, Co2+, and Fe3+. The effects of metal ion concentration and pH were evaluated for the ion having the highest activity. Conbination of PAA and UV light was also tested.In this study, the variation of the dye concentration was monitored by measuring light absorption at the maximum absorption wavelength of Reactive Orange 122 (at 493 nm). The obtained results showed that Co2+ion has the highest catalytic activity. The rate of decolorization increases as the concentration of Co2+ and pH increases. Under UV light irradiation, PAA exhibited higher activity comparing to H2O2. This phenomenon can be explained by weaker O-O linkage in PAA.
 Keywords
 Peracetic acid, reactive orange 122, kinetics, UV light.
 References
 [1] P. Krizman , F. Kovac, P. F. Tavcer, Bleaching of cotton fabric with peracetic acid in the presence of different activators, Color. Technol. 121 (2005) 304 - 309.[2] D. P. Barros, V. L. Silva, H. Hamalainen, J. L. Colodette, Effect of last stage bleaching with peracetic acid on brightness development and properties of eucalyptus pulp, Bioresource 5 (2) (2010) 881 - 898.[3] D. S. R. Gehr, T. A. Bartrand, L. Liberti, M. Notarnicola, A. Dell’Erba, D. Falsanisi, C. N. Haas, Wastewater Disinfection by Peracetic Acid:Assessment of Models for Tracking Residual Measurements and Inactivation, Water Environment Research 79 (7) (2007) 775 - 787. [4] M. Kitis, Disinfection of wastewater with peraceticacid: a review, Environment International 30 (2004) 47–55.[5] S. Bonetta, C. Pignata, E. Lorenzi, M. D. Ceglia,L. M., S. Bonetta, G. Gilli, E. Carraro, Peracetic Acid (PAA) Disinfection: Inactivation ofMicrobial Indicators and Pathogenic Bacteria ina Municipal Wastewater Plant, Water 9 (2017) 427 https://doi.org/10.3390/w9060427.[6] R. D. Bach, P. Y. Ayala, H. B. Schlegel, A Reassessment of the Bond Dissociation Energies ofPeroxides. An ab Initio Study, J. Am. Chem. Soc. 118 (1996) 12758-12765.[7] H. M. N. H. IrvingR. J. P. Williams, The stability of transition-metal complexes, J. Chem. Soc. (1953) 3192

Stability of transition metal complexes involving three isomeric quinolyl hydrazones

The stability constants of three isomeric quinolyl hydrazones; {4,6-(para); 4,7-(meta) and 4,8-MeBHQ(ortho)} towards some bivalent metal ions have been determined in 75% solvent (dioxane, isopropanol, ethanol and methanol)–water by a pH-titrimetry. The insertion of the Me-group in the 8-position decreases the stability of the complexes to a great extent. The complexation of the ortho-derivative is endothermic, whereas that of the para-derivative is exothermic. Using the solvent parameters, the stability constants of the para-derivative towards Co(II), Ni(II) and Cu(II) ions were evaluated in aqueous medium by five different methods. Also, the electronic absorption spectra of the ortho-hydrazone have been studied in solvents of various polarities to investigate the dependence of the band shift (Δ ύ) on the solvent parameters viz. 1/ D, Z, E T, DN, AN and (α, β, π*). The interaction of the hydrazones with CoCl 2·6H 2O afforded an octahedral complex in case of the ortho-hydrazone and square planar complexes in case of the meta- and para-hydrazones.

ChemInform Abstract: Carbodiphosphoranes and Related Ligands

AbstractReview: 149 refs.

Stability of transition metal complexes with sulfonated polymers

Stability constants of macromolecular metallocomplexes of transition metal ions (Ag+, Cu2+, Ni2+, Fe3+) with sulfonated polymers in water and aqueous HCl and NaCl solutions were determined from quenching by transition metal ions of the luminescence of macromolecules labeled with luminescent groups.

Characterization and stability of transition metal complexes of chestnut (Castanea sativa L.) leaf litter

SUMMARYThe water‐ and acid‐insoluble fractions of a chestnut (Castanea sativa L.) leaf litter sample and their complexes with Cu(II), Fe(III), and Mn(II) prepared in the laboratory were characterized by major elemental analysis, total Cu, Fe, and Mn content, infrared (IR), and electron spin resonance (ESR) spectroscopy. The IR spectra revealed a broad typology of functional groups (particularly carboxyls) in the solid litter, whereas the ESR spectra showed the existence of indigenous organic free radical species, inner‐sphere Fe3+ complexes, and outer‐sphere Mn2+ complexes. The litter exhibited a high residual binding capacity for Cu, Fe, and Mn in chemical forms of differing stability against water leaching and proton exchange. The ESR spectra of the metal complexes prepared in the laboratory indicated that Fe3+ and Cu2+ formed highly water‐stable, inner‐sphere complexes, whereas Mn2+ formed water‐labile, outer‐sphere complexes. Oxygen ligands of the litter were involved in metal complexation in all cases. The litter showed the highest affinity for Cu2+, followed by Fe3+ and Mn2+, when it was reacted with a single metal, whereas it complexed Fe3+ preferentially in the presence of both Cu2+ and Fe3+. Only a limited portion of the metal ions retained at the pH of distilled water remained bound in stable forms by the litter when the pH was lowered. Thus, variations of pH in forest soils will significantly affect micronutrient metal content and mobility in leaf litter.

Theoretical study on the structure of methyltitanium complexes: analysis by Paired Interacting Orbitals (PIO)

The origin of the formation of a CH → Ti bond in a methyltitanium complex was studied by use of Paired Interacting Orbitals (PIO). Methyl group tilt is flavoured when there is a ligand trans to the methyl. An electron-donating ligand axial to the tilting plane causes methyl to tilt into an agostic position. This methyl group tilt in the opposite direction is not favoured because of the overlap repulsion between the ligand orbital and orbitals of the methyl group. The PIO technique elucidates the properties such as structures, reactivity and stability of transition metal complexes.

Stabilization of transition-metal complexes in high oxidation states by macrocyclic tertiary amines. Electrochemical generation and spectroscopic properties of novel dihalogeno and pseudohalogeno tetraamine complexes of ruthenium(IV)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStabilization of transition-metal complexes in high oxidation states by macrocyclic tertiary amines. Electrochemical generation and spectroscopic properties of novel dihalogeno and pseudohalogeno tetraamine complexes of ruthenium(IV)Chi Ming Che, Kwok Yin Wong, and Chung Kwong PoonCite this: Inorg. Chem. 1986, 25, 11, 1809–1813Publication Date (Print):May 1, 1986Publication History Published online1 May 2002Published inissue 1 May 1986https://doi.org/10.1021/ic00231a020RIGHTS & PERMISSIONSArticle Views407Altmetric-Citations30LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (603 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Correlation of the 1.R. data with the stability of transition metal complexes of 8-amino-7-hydroxy-4-methylcoumarin

The i.r. spectra of a number of solid transition metal complexes of AHMC have been investigated and it has been possible to determine three vibrations of the ligated molecules in these complexes. The decrease in stretching NH 2 vibrations have been observed in the region 3320-3200 cm −1; the NH 2 rocking deformation in the region 790-650 cm −1 and the metal-nitrogen stretching frequencies in the region 510−480 cm −1. On the basis of these frequencies a correlation has been sought in with the stability of transition metal complexes which is supported by their 10 D q values.

Cation toxicity and the stability of transition-metal complexes.

DESPITE the many important contributions that have been made to the literature during the past century, no completely satisfactory theory of cation toxicity has been formulated. Blake1 first concluded that there was a correlation between degree of toxicity and atomic weight (hence ‘heavy-metal’ poisons). Matthews2 and Jones3 later pointed out a relationship between metal ion toxicity and the ‘solution pressure’ (standard electrode potential) of the corresponding metals. Seifriz4 considered various other chemical properties of the ions in his attempt to find a satisfactory chemical explanation for the relative toxicity of cations. Shaw5–7, basing his arguments on results obtained with enzymes, postulated that metal ions killed aquatic organisms by combining with an essential group (probably—SH) on a key enzyme. Correlation with metal sulphide insolubility was demonstrated. An attempt was also made6 to relate the relative inhibitory efficiency of bivalent metal ions toward the enzyme urease with metal complex stability. At that time (early 1953), however, the field of co-ordination chemistry had not reached a stage of sufficient maturity for such a comparison to be successfully made. The explosive growth that has occurred during the past decade in our knowledge of the chemistry of co-ordination compounds necessitates a re-examination of the intriguing possibility that there exists a relationship between metal complex stability and the toxicity of metal ions to living organisms.

On the stabilities of transition metal complexes—I Theory of the energies

A molecular orbital theory of the energies of formation of transition metal complexes is presented. The energies of pairing of d-electrons in covalent regular octahedral d n -complexes are calculated in terms of atomic spectral parameters. It is then shown, by means of a hole formalism, that the pairing energies for regular tetrahedral d 10− n -complexes are formally the same. A reason is suggested as to why regular complexes with certain spins, which are apparently possible in principle, are unknown experimentally. Certain aspects of the electrostatic crystal-field theory are briefly compared with the present treatment.

637. The stability of transition-metal complexes

637. The stability of transition-metal complexes