Studies on transition-metal-peptide complexes. Part 6. Influence of side-chain donor group on the equilibrium and thermodynamics of binary and ternary copper(II)-dipeptide complexes

Arthur Gergely, E. Farkas

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Abstract

Copper(II) binary and ternary complexes of dipeptides containing amide carbonyl, alcoholic hydroxy, and carboxy groups in their side-chain have been studied. The dipeptides (A ligands) were glycyl-L-serine (GlySer), glycyl-L-asparagine (GlyAsn), glycyl-L-aspartic acid (GlyAsp), and glycyl-L-glutamic acid (GlyGlu). In the case of copper(II)-dipeptide ternary complexes, L/D-α-alanine (α-Ala), β-alanine (β-Ala), L/D-aspartic acid (Asp), L/D-ornithine (Orn), and 2,2′-bipyridyl (bipy) were used as B ligands. pH-Titrimetry and calorimetry were applied to determine the stability constants and the enthalpy and entropy changes of the species formed in the systems studied. It was assumed that the carboxylate group in the GlyAsp side-chain co-ordinates in the axial position to copper(II). Above pH 10, deprotonation of the amide carbonyl in GlyAsn takes place, accompanied by its bonding in the square plane to copper(II). A [CuAB] type complex is formed in high concentration, mainly with bipy as B ligand. However, [CuABH-1] type deprotonated species are also formed in the case of copper(II)-dipeptide-amino-acid systems. Stereoselectivity in this complex was observed only with Asp and Orn. This effect may presumably be attributed to electrostatic interactions. Thermodynamic data support the assumption of bipy occupying two equatorial positions in [CuAB] species, and an equatorial and an axial position in [CuABH-1].

Original languageEnglish
Pages (from-to)381-386
Number of pages6
JournalJournal of the Chemical Society, Dalton Transactions
Issue number2
DOIs
Publication statusPublished - 1982

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Dipeptides
Transition metals
Copper
2,2'-Dipyridyl
Thermodynamics
Peptides
Ornithine
Asparagine
Ligands
Amides
Alanine
D-Aspartic Acid
Stereoselectivity
Deprotonation
Calorimetry
Coulomb interactions
Aspartic Acid
Serine
Glutamic Acid
Enthalpy

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Studies on transition-metal-peptide complexes. Part 6. Influence of side-chain donor group on the equilibrium and thermodynamics of binary and ternary copper(II)-dipeptide complexes",
abstract = "Copper(II) binary and ternary complexes of dipeptides containing amide carbonyl, alcoholic hydroxy, and carboxy groups in their side-chain have been studied. The dipeptides (A ligands) were glycyl-L-serine (GlySer), glycyl-L-asparagine (GlyAsn), glycyl-L-aspartic acid (GlyAsp), and glycyl-L-glutamic acid (GlyGlu). In the case of copper(II)-dipeptide ternary complexes, L/D-α-alanine (α-Ala), β-alanine (β-Ala), L/D-aspartic acid (Asp), L/D-ornithine (Orn), and 2,2′-bipyridyl (bipy) were used as B ligands. pH-Titrimetry and calorimetry were applied to determine the stability constants and the enthalpy and entropy changes of the species formed in the systems studied. It was assumed that the carboxylate group in the GlyAsp side-chain co-ordinates in the axial position to copper(II). Above pH 10, deprotonation of the amide carbonyl in GlyAsn takes place, accompanied by its bonding in the square plane to copper(II). A [CuAB] type complex is formed in high concentration, mainly with bipy as B ligand. However, [CuABH-1] type deprotonated species are also formed in the case of copper(II)-dipeptide-amino-acid systems. Stereoselectivity in this complex was observed only with Asp and Orn. This effect may presumably be attributed to electrostatic interactions. Thermodynamic data support the assumption of bipy occupying two equatorial positions in [CuAB] species, and an equatorial and an axial position in [CuABH-1].",
author = "Arthur Gergely and E. Farkas",
year = "1982",
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T1 - Studies on transition-metal-peptide complexes. Part 6. Influence of side-chain donor group on the equilibrium and thermodynamics of binary and ternary copper(II)-dipeptide complexes

AU - Gergely, Arthur

AU - Farkas, E.

PY - 1982

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N2 - Copper(II) binary and ternary complexes of dipeptides containing amide carbonyl, alcoholic hydroxy, and carboxy groups in their side-chain have been studied. The dipeptides (A ligands) were glycyl-L-serine (GlySer), glycyl-L-asparagine (GlyAsn), glycyl-L-aspartic acid (GlyAsp), and glycyl-L-glutamic acid (GlyGlu). In the case of copper(II)-dipeptide ternary complexes, L/D-α-alanine (α-Ala), β-alanine (β-Ala), L/D-aspartic acid (Asp), L/D-ornithine (Orn), and 2,2′-bipyridyl (bipy) were used as B ligands. pH-Titrimetry and calorimetry were applied to determine the stability constants and the enthalpy and entropy changes of the species formed in the systems studied. It was assumed that the carboxylate group in the GlyAsp side-chain co-ordinates in the axial position to copper(II). Above pH 10, deprotonation of the amide carbonyl in GlyAsn takes place, accompanied by its bonding in the square plane to copper(II). A [CuAB] type complex is formed in high concentration, mainly with bipy as B ligand. However, [CuABH-1] type deprotonated species are also formed in the case of copper(II)-dipeptide-amino-acid systems. Stereoselectivity in this complex was observed only with Asp and Orn. This effect may presumably be attributed to electrostatic interactions. Thermodynamic data support the assumption of bipy occupying two equatorial positions in [CuAB] species, and an equatorial and an axial position in [CuABH-1].

AB - Copper(II) binary and ternary complexes of dipeptides containing amide carbonyl, alcoholic hydroxy, and carboxy groups in their side-chain have been studied. The dipeptides (A ligands) were glycyl-L-serine (GlySer), glycyl-L-asparagine (GlyAsn), glycyl-L-aspartic acid (GlyAsp), and glycyl-L-glutamic acid (GlyGlu). In the case of copper(II)-dipeptide ternary complexes, L/D-α-alanine (α-Ala), β-alanine (β-Ala), L/D-aspartic acid (Asp), L/D-ornithine (Orn), and 2,2′-bipyridyl (bipy) were used as B ligands. pH-Titrimetry and calorimetry were applied to determine the stability constants and the enthalpy and entropy changes of the species formed in the systems studied. It was assumed that the carboxylate group in the GlyAsp side-chain co-ordinates in the axial position to copper(II). Above pH 10, deprotonation of the amide carbonyl in GlyAsn takes place, accompanied by its bonding in the square plane to copper(II). A [CuAB] type complex is formed in high concentration, mainly with bipy as B ligand. However, [CuABH-1] type deprotonated species are also formed in the case of copper(II)-dipeptide-amino-acid systems. Stereoselectivity in this complex was observed only with Asp and Orn. This effect may presumably be attributed to electrostatic interactions. Thermodynamic data support the assumption of bipy occupying two equatorial positions in [CuAB] species, and an equatorial and an axial position in [CuABH-1].

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