Kinetic studies on four-coordinate chelate complexes of copper(II): isotopic ligand exchange of bis(salicylaldiminato)copper(II) in toluene

Voss, H.; Wannowius, Klaus J.; Elias, Horst

doi:10.1021/ic50196a010

Cited by 10 publications

(5 citation statements)

References 2 publications

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“…BTA exhibits strong complexing capability . 2,4-DCP and especially 1,4-D are very weak ligands. − Toluene nearly cannot coordinate with copper . The high efficiency of Cu(II)/PMS in removing all these compounds suggests that the strong Cu(II)–pollutant coordination is not an indispensable factor for the Cu(II)-triggered PMS oxidation.…”

Section: Resultsmentioning

confidence: 99%

Trace Cupric Species Triggered Decomposition of Peroxymonosulfate and Degradation of Organic Pollutants: Cu(III) Being the Primary and Selective Intermediate Oxidant

Wang

Jiang

et al. 2020

Environ. Sci. Technol.

341

139

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Activation of persulfates to degrade refractory organic pollutants is currently a hot topic of advanced oxidation. Developing simple and effective activation approaches is crucial for the practical application of persulfates. We report in this research that trace cupric species (Cu(II) in several μM) can efficiently trigger peroxymonosulfate (PMS) oxidation of various organic pollutants under slightly alkaline conditions. The intermediate oxidant dominating this process was investigated with electron paramagnetic resonance (EPR), chemical probing, and in situ Raman spectroscopy. Unlike conventional PMS activation, which generates sulfate radical, hydroxyl radical, or singlet oxygen as major oxidants, Cu(III) was confirmed to be the primary and selective intermediate oxidant during the Cu(II)/PMS oxidation. Hydroxyl radical is the secondary intermediate oxidant formed from the reaction of Cu(III) with OH − . Hybrid oxidation by the two oxidants imparts Cu(II)/PMS with high efficiency in the degradation of a series of pollutants. The results of this work suggest that, with no need of introducing complex catalysts, trace Cu(II) inherent in or artificially introduced to some water or wastewater can effectively trigger PMS oxidation of organic pollutants.

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Section: Resultsmentioning

confidence: 99%

Trace Cupric Species Triggered Decomposition of Peroxymonosulfate and Degradation of Organic Pollutants: Cu(III) Being the Primary and Selective Intermediate Oxidant

Wang

Jiang

et al. 2020

Environ. Sci. Technol.

341

139

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“…These low values cannot be simply attributed to the susceptibility to ligand substitution of copper( II ) ions, since similar values should then be observed with catechols. Furthermore, ligand substitutions in copper( II ) model complexes are associated with much larger activation enthalpies, ranging from 25 to 85 kJ mol −1 , depending on the complex and the reaction conditions 52–54. Therefore, at least for phenolic substrates, the hypothesis of slow binding to tyrosinase is unlikely.…”

Section: Discussionmentioning

confidence: 99%

Mechanistic Insight into the Activity of Tyrosinase from Variable‐Temperature Studies in an Aqueous/Organic Solvent

Granata

Monzani

Bubacco

et al. 2006

Chemistry A European J

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The activity of mushroom tyrosinase towards a representative series of phenolic and diphenolic substrates structurally related to tyrosine has been investigated in a mixed solvent of 34.4% methanol-glycerol (7:1, v/v) and 65.6% (v/v) aqueous 50 mM Hepes buffer at pH 6.8 at various temperatures. The kinetic activation parameters controlling the enzymatic reactions and the thermodynamic parameters associated with the process of substrate binding to the enzyme active species have been deduced from the temperature variation of the kcat and KM parameters. The activation free energy is dominated by the enthalpic term, the value of which lies in the relatively narrow range of 61+/-9 kJ mol(-1) irrespective of substrate or reaction type (monophenolase or diphenolase). The activation entropies are small and generally negative and contribute no more than 10% to the activation free energy. The substrate binding parameters are characterized by large and negative enthalpy and entropy contributions, which are typically dictated by polar protein-substrate interactions. The substrate 4-hydroxyphenylpropionic acid exhibits a strikingly anomalous temperature dependence of the enzymatic oxidation rate, with deltaH(double dagger) approximately = 150 kJ mol(-1) and deltaS(double dagger) approximately = 280 J K(-1) mol(-1), due to the fact that it can competitively bind to the enzyme through the phenol group, like the other substrates, or the carboxylate group, like carboxylic acid inhibitors. A kinetic model that takes into account the dual substrate/inhibitor nature of this compound enables rationalization of this anomalous behavior.

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“…The commercially available amines RNH 2 and 5-X-salicylaldehydes (see Chart for R and X) and the salt VOSO 4 ·5H 2 O were used without further purification. 5-Bromosalicylaldehyde and 5-methylsalicylaldehyde were prepared as described earlier . The solvent acetone (analytical grade, Merck) was used without further purification ([H 2 O] = 0.04 M, as determined by Karl Fischer titration).…”

Section: Methodsmentioning

confidence: 99%

Kinetics and Mechanism of Ligand Substitution in Bis(N-alkylsalicylaldiminato)oxovanadium(IV) Complexes

2003

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Conventional and stopped-flow spectrophotometry was used to to study the kinetics of ligand substitution in a number of bis(N-alkylsalicylaldiminato)oxovanadium(IV) complexes (=VO(R-X-sal)(2)) by 1,1,1- trifluoropentane-2,4-dione (=Htfpd) in acetone, according to the following reaction: VO(R-X-sal)(2) + 2Htfpd --> VO(tfpd)(2) + 2R-X-salH. The acronym R-X-salH refers to N-alkylsalicylaldimines with substituents X = H, Cl, Br, CH(3), and NO(2) in the 5-position of the salicylaldehyde ring and N-alkyl groups R = n-propyl, isopropyl, phenyl, and neopentyl. Under excess conditions ([Htfpd](0) >> [VO(R-X-sal)(2)](0)), substitution by Htfpd occurs in two observable steps, as characterized by pseudo-first-order rate constants k(obsd(1)) and k(obsd(2)). Both rate constants increase linearly with [Htfpd](0) according to k(obsd(1)) = k(s(1)) + k(1)[Htfpd](0) and k(obsd(2)) = k(s(2)) + k(2)[Htfpd](0), with k(s(1)) and k(s(2)) describing small contributions of solvent-initiated pathways. Depending on the nature of R and X, second-order rate constants k(1) and k(2) lie in the range 0.098-0.87 M(-1) s(-1) (k(1)) and 0.022-0.41 M(-1) s(-1) (k(2)) at 298 K. For ligand substitution in the system VO(n-propyl-sal)(2)/Htfpd, the activation parameters DeltaH++ = 35.8 +/- 2.8 kJ mol(-1) and DeltaS++ = -146 +/- 23 J K(-1) mol(-1) (k(1)) and DeltaH++ = 40.2 +/- 1.3 kJ mol(-1) and DeltaS++ = -142 +/- 11 J K(-1) mol(-1) (k(2)) were obtained. The Lewis acidity of the complexes VO(n-propyl-X-sal)(2) with X = H, Cl, Br, CH(3), and NO(2) was quantified spectrophotometrically by determination of equilibrium constant K(py), describing the formation of the adduct VO(n-propyl-X-sal)(2).pyridine. The adduct VO(tfpd)(2).n-propyl-salH, formed as product in the system VO(n-propyl-sal)(2)/Htfpd, was characterized by its dissociation constant, K(D) = (3.30 +/- 0.10) x 10(-3) M. The mechanism suggested for the two-step substitution process is based on initial formation of the adducts VO(R-X-sal)(2).Htfpd (step 1) and VO(R-X-sal)(tfpd).Htfpd (step 2).

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Kinetic studies on four-coordinate chelate complexes of copper(II): isotopic ligand exchange of bis(salicylaldiminato)copper(II) in toluene

Cited by 10 publications

References 2 publications

Trace Cupric Species Triggered Decomposition of Peroxymonosulfate and Degradation of Organic Pollutants: Cu(III) Being the Primary and Selective Intermediate Oxidant

Trace Cupric Species Triggered Decomposition of Peroxymonosulfate and Degradation of Organic Pollutants: Cu(III) Being the Primary and Selective Intermediate Oxidant

Mechanistic Insight into the Activity of Tyrosinase from Variable‐Temperature Studies in an Aqueous/Organic Solvent

Kinetics and Mechanism of Ligand Substitution in Bis(N-alkylsalicylaldiminato)oxovanadium(IV) Complexes

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