New functional model complexes of intradiol-cleaving catechol dioxygenases: Properties and reactivity of CuII(L)(O2Ncat)

József Kaizer, Zoltán Zsigmond, Ildiko Ganszky, Gábor Speier, Michel Giorgi, Marius Réglier

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21 Citations (Scopus)

Abstract

Complexes Cu(O2Ncat)(tbeda) (1) and Cu(O2Ncat)(tmeda) (2) (tbeda = N,N,N′,N′-tetrabenzylethylenediamine, tmeda = N,N,N′,N′-tetramethylethylenenediamine, O2NcatH 2 = 4-nitrocatechol) have been prepared by the reaction of copper(II) perchlorate with 4-nitrocatechol in the presence of triethylamine and the appropriate bidentate ligand. These compounds represent structural and functional model systems for the copper-containing catechol 1,2-dioxygenase. Both complexes have been structurally characterized by X-ray crystallography and by UV-vis, IR, and EPR spectroscopies. Upon protonation of 1 and 2 with perchloric acid, the bidentate coordination of O2-Ncat could be reversible converted to the monodentate coordination of O2NcatH. The equilibrium constants were found to be 4200 and 3500, respectively, by measuring the UV-vis spectra in DMF. Back-titration with morpholine proved the reversibility of both reactions. Kinetic data on the oxygenation of 1 and 2 revealed overall second-order rate equations with kinetic parameters: k tbeda = (4.63 ± 0.23) × 10-2 mol-1 dm3 s-1, ΔH = 51 ± 6 kJ mol-1, ΔS = -137 ± 16 J mol-1 K-1; ktmeda = (0.89 ± 0.23) mol-1 dm3 s-1, ΔH = 85 ± 7 kJ mol-1, ΔS = -57 ± 19 J mol-1 K-1 at 365.16 K. Oxygenation of 1, 2, and [Cu(O2NcatH)(L)] ClO4 (L = tbeda, tmeda) in DMF solution at ambient conditions gives the corresponding intradiol ring-cleaved (2-nitro-muconato)copper(II) complexes. These data support the assumption that the reaction of the differently coordinated catecholate ligand with dioxygen shows only 1,2-dioxygenase activity.

Original languageEnglish
Pages (from-to)4660-4666
Number of pages7
JournalInorganic Chemistry
Volume46
Issue number11
DOIs
Publication statusPublished - May 28 2007

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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