Metal complexes of imidazole ligands containing histamine-like donor sets: Equilibrium, solution structure and hydrolytic activity

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Abstract

The equilibrium and structural properties of copper(II) and zinc(II) complexes of N,N′-di-L-histidylethane-1,2-diamine (dhen) and those of the strongly related histamine have been characterized by pH-metric and spectroscopic (UV/VIS, CD, EPR and NMR) methods. In both dhen systems a dimeric M2L2 species is dominant near the physiological pH, having bis(histamine-like) 2N1m, 2NH2 co-ordination. The MLH-2 complex, also formed in both systems above pH 10, has different structures with the two metal ions. A hydroxo mixed-ligand complex is formed in the case of zinc(II), while the base-consuming processes are assigned to metal-promoted deprotonation of amide nitrogens in the copper(II) system. Between these two dominant species (pH 7-10) tetrameric complexes are formed in each case (as suggested by the CD, EPR and NMR results), with the participation of imidazole-N1 (pyrrolic) nitrogen in the co-ordination. The catalytic activity of the zinc(II)-containing systems towards the hydrolysis of uridine 2′,3′-cyclic monophosphate as nuclease model has been examined. The zinc(II)-histamine complexes efficiently catalyse the hydrolysis. A kinetic study performed at different pH, concentrations and metal-to-ligand ratios, combined with the equilibrium data, revealed three reaction pathways involving Zn(OH), ZnL and ZnL(OH) complexes as active species, in order of activity ZnL ≪ Zn(OH) <ZnL(OH).

Original languageEnglish
Pages (from-to)1205-1212
Number of pages8
JournalJournal of the Chemical Society, Dalton Transactions
Issue number7
Publication statusPublished - Apr 7 1998

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Coordination Complexes
Histamine
Zinc
Ligands
Paramagnetic resonance
Copper
Hydrolysis
Nitrogen
Metals
Nuclear magnetic resonance
Deprotonation
Diamines
Uridine
Amides
Metal ions
Structural properties
Catalyst activity
Kinetics
imidazole

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

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title = "Metal complexes of imidazole ligands containing histamine-like donor sets: Equilibrium, solution structure and hydrolytic activity",
abstract = "The equilibrium and structural properties of copper(II) and zinc(II) complexes of N,N′-di-L-histidylethane-1,2-diamine (dhen) and those of the strongly related histamine have been characterized by pH-metric and spectroscopic (UV/VIS, CD, EPR and NMR) methods. In both dhen systems a dimeric M2L2 species is dominant near the physiological pH, having bis(histamine-like) 2N1m, 2NH2 co-ordination. The MLH-2 complex, also formed in both systems above pH 10, has different structures with the two metal ions. A hydroxo mixed-ligand complex is formed in the case of zinc(II), while the base-consuming processes are assigned to metal-promoted deprotonation of amide nitrogens in the copper(II) system. Between these two dominant species (pH 7-10) tetrameric complexes are formed in each case (as suggested by the CD, EPR and NMR results), with the participation of imidazole-N1 (pyrrolic) nitrogen in the co-ordination. The catalytic activity of the zinc(II)-containing systems towards the hydrolysis of uridine 2′,3′-cyclic monophosphate as nuclease model has been examined. The zinc(II)-histamine complexes efficiently catalyse the hydrolysis. A kinetic study performed at different pH, concentrations and metal-to-ligand ratios, combined with the equilibrium data, revealed three reaction pathways involving Zn(OH), ZnL and ZnL(OH) complexes as active species, in order of activity ZnL ≪ Zn(OH) <ZnL(OH).",
author = "Ibolya T{\"o}r{\"o}k and T. Gajda and B. Gyurcsik and G. T{\'o}th and A. P{\'e}ter",
year = "1998",
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T1 - Metal complexes of imidazole ligands containing histamine-like donor sets

T2 - Equilibrium, solution structure and hydrolytic activity

AU - Török, Ibolya

AU - Gajda, T.

AU - Gyurcsik, B.

AU - Tóth, G.

AU - Péter, A.

PY - 1998/4/7

Y1 - 1998/4/7

N2 - The equilibrium and structural properties of copper(II) and zinc(II) complexes of N,N′-di-L-histidylethane-1,2-diamine (dhen) and those of the strongly related histamine have been characterized by pH-metric and spectroscopic (UV/VIS, CD, EPR and NMR) methods. In both dhen systems a dimeric M2L2 species is dominant near the physiological pH, having bis(histamine-like) 2N1m, 2NH2 co-ordination. The MLH-2 complex, also formed in both systems above pH 10, has different structures with the two metal ions. A hydroxo mixed-ligand complex is formed in the case of zinc(II), while the base-consuming processes are assigned to metal-promoted deprotonation of amide nitrogens in the copper(II) system. Between these two dominant species (pH 7-10) tetrameric complexes are formed in each case (as suggested by the CD, EPR and NMR results), with the participation of imidazole-N1 (pyrrolic) nitrogen in the co-ordination. The catalytic activity of the zinc(II)-containing systems towards the hydrolysis of uridine 2′,3′-cyclic monophosphate as nuclease model has been examined. The zinc(II)-histamine complexes efficiently catalyse the hydrolysis. A kinetic study performed at different pH, concentrations and metal-to-ligand ratios, combined with the equilibrium data, revealed three reaction pathways involving Zn(OH), ZnL and ZnL(OH) complexes as active species, in order of activity ZnL ≪ Zn(OH) <ZnL(OH).

AB - The equilibrium and structural properties of copper(II) and zinc(II) complexes of N,N′-di-L-histidylethane-1,2-diamine (dhen) and those of the strongly related histamine have been characterized by pH-metric and spectroscopic (UV/VIS, CD, EPR and NMR) methods. In both dhen systems a dimeric M2L2 species is dominant near the physiological pH, having bis(histamine-like) 2N1m, 2NH2 co-ordination. The MLH-2 complex, also formed in both systems above pH 10, has different structures with the two metal ions. A hydroxo mixed-ligand complex is formed in the case of zinc(II), while the base-consuming processes are assigned to metal-promoted deprotonation of amide nitrogens in the copper(II) system. Between these two dominant species (pH 7-10) tetrameric complexes are formed in each case (as suggested by the CD, EPR and NMR results), with the participation of imidazole-N1 (pyrrolic) nitrogen in the co-ordination. The catalytic activity of the zinc(II)-containing systems towards the hydrolysis of uridine 2′,3′-cyclic monophosphate as nuclease model has been examined. The zinc(II)-histamine complexes efficiently catalyse the hydrolysis. A kinetic study performed at different pH, concentrations and metal-to-ligand ratios, combined with the equilibrium data, revealed three reaction pathways involving Zn(OH), ZnL and ZnL(OH) complexes as active species, in order of activity ZnL ≪ Zn(OH) <ZnL(OH).

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