An ESR study of co-ordination modes in copper(II) complexes of l-serine in aqueous solution at ligand excess above pH 7

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Abstract

Co-ordination modes for the bis complexes of l-serine with copper(II) ion have been studied in fluid aqueous solution by ESR spectroscopy. The computer analysis of a series of overlapping spectra taken in neutral and alkaline solutions was carried out including one to four independent species. For the component spectra a hyperfine splitting by isotopes 63Cu and 65Cu and two equivalent nitrogen atoms were taken into consideration. The isotropic ESR parameters and relative concentrations of different species were optimized. The distribution of copper(II) amongst different species is in accordance with literature formation constants obtained by pH-metric and spectrophotometric studies. For both the [CuL2] and [CuL2H-1]- complexes two kinds of co-ordination exist. The spectra of smaller copper and nitrogen hyperfine coupling constants, which give the major contribution to the experimental curves, are assigned to the cis isomer, while the minor species is the trans isomer of higher hyperfine coupling constants. For the complex [CuL2H-2]2- only one mode of co-ordination exists with cis arrangement of the equatorial N and O donor atoms, respectively. The values of ESR parameters indicate the equatorial binding of deprotonated OH groups of side chains and a geometric distortion of the cis complexes.

Original languageEnglish
Pages (from-to)1969-1974
Number of pages6
JournalPolyhedron
Volume18
Issue number14
Publication statusPublished - May 28 1999

Fingerprint

Serine
Paramagnetic resonance
Copper
Ligands
aqueous solutions
Isomers
copper
ligands
Nitrogen
isomers
Atoms
Isotopes
nitrogen atoms
Spectrum Analysis
isotopes
Spectroscopy
Ions
nitrogen
Fluids
fluids

Keywords

  • Co-ordination
  • Copper(II) complexes
  • ESR
  • Isomerism
  • L-Serine

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

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title = "An ESR study of co-ordination modes in copper(II) complexes of l-serine in aqueous solution at ligand excess above pH 7",
abstract = "Co-ordination modes for the bis complexes of l-serine with copper(II) ion have been studied in fluid aqueous solution by ESR spectroscopy. The computer analysis of a series of overlapping spectra taken in neutral and alkaline solutions was carried out including one to four independent species. For the component spectra a hyperfine splitting by isotopes 63Cu and 65Cu and two equivalent nitrogen atoms were taken into consideration. The isotropic ESR parameters and relative concentrations of different species were optimized. The distribution of copper(II) amongst different species is in accordance with literature formation constants obtained by pH-metric and spectrophotometric studies. For both the [CuL2] and [CuL2H-1]- complexes two kinds of co-ordination exist. The spectra of smaller copper and nitrogen hyperfine coupling constants, which give the major contribution to the experimental curves, are assigned to the cis isomer, while the minor species is the trans isomer of higher hyperfine coupling constants. For the complex [CuL2H-2]2- only one mode of co-ordination exists with cis arrangement of the equatorial N and O donor atoms, respectively. The values of ESR parameters indicate the equatorial binding of deprotonated OH groups of side chains and a geometric distortion of the cis complexes.",
keywords = "Co-ordination, Copper(II) complexes, ESR, Isomerism, L-Serine",
author = "T. Szab{\'o}-Pl{\'a}nka and A. Rockenbauer and L. Korecz",
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T1 - An ESR study of co-ordination modes in copper(II) complexes of l-serine in aqueous solution at ligand excess above pH 7

AU - Szabó-Plánka, T.

AU - Rockenbauer, A.

AU - Korecz, L.

PY - 1999/5/28

Y1 - 1999/5/28

N2 - Co-ordination modes for the bis complexes of l-serine with copper(II) ion have been studied in fluid aqueous solution by ESR spectroscopy. The computer analysis of a series of overlapping spectra taken in neutral and alkaline solutions was carried out including one to four independent species. For the component spectra a hyperfine splitting by isotopes 63Cu and 65Cu and two equivalent nitrogen atoms were taken into consideration. The isotropic ESR parameters and relative concentrations of different species were optimized. The distribution of copper(II) amongst different species is in accordance with literature formation constants obtained by pH-metric and spectrophotometric studies. For both the [CuL2] and [CuL2H-1]- complexes two kinds of co-ordination exist. The spectra of smaller copper and nitrogen hyperfine coupling constants, which give the major contribution to the experimental curves, are assigned to the cis isomer, while the minor species is the trans isomer of higher hyperfine coupling constants. For the complex [CuL2H-2]2- only one mode of co-ordination exists with cis arrangement of the equatorial N and O donor atoms, respectively. The values of ESR parameters indicate the equatorial binding of deprotonated OH groups of side chains and a geometric distortion of the cis complexes.

AB - Co-ordination modes for the bis complexes of l-serine with copper(II) ion have been studied in fluid aqueous solution by ESR spectroscopy. The computer analysis of a series of overlapping spectra taken in neutral and alkaline solutions was carried out including one to four independent species. For the component spectra a hyperfine splitting by isotopes 63Cu and 65Cu and two equivalent nitrogen atoms were taken into consideration. The isotropic ESR parameters and relative concentrations of different species were optimized. The distribution of copper(II) amongst different species is in accordance with literature formation constants obtained by pH-metric and spectrophotometric studies. For both the [CuL2] and [CuL2H-1]- complexes two kinds of co-ordination exist. The spectra of smaller copper and nitrogen hyperfine coupling constants, which give the major contribution to the experimental curves, are assigned to the cis isomer, while the minor species is the trans isomer of higher hyperfine coupling constants. For the complex [CuL2H-2]2- only one mode of co-ordination exists with cis arrangement of the equatorial N and O donor atoms, respectively. The values of ESR parameters indicate the equatorial binding of deprotonated OH groups of side chains and a geometric distortion of the cis complexes.

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