Effect of fluorine position on the coordinating ability of fluorosalicylic acids - An experimental study complemented with computations

T. Szabó-Plánka, B. Gyurcsik, I. Pálinkó, N. Nagy, A. Rockenbauer, Rastislav Šípoš, Jozef Šima, Milan Melník

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Abstract

The complexation of 3-, 4-, and 6-fluorosalicylic acids (HL) with copper(II) was investigated in aqueous solution by pH-potentiometry combined with UV-visible spectrophotometry, and in 50 v/v % water-methanol mixture by the two-dimensional ESR simulation method. Both methods showed the formation of [CuLH-1] and [CuL2H-2]2- of high stabilities, and, at low excess of ligand, the ESR-silent mixed hydroxido complex [Cu2L2H-3]-. Further species were also identified by the two-dimensional ESR simulation method: [CuL] + in the acidic region, the minor dimer [Cu2L 2H-2], and the cis and the trans isomers for [CuL 2H-2]2-. The position of the fluorine atom in the aromatic ring had significant effect on the coordination abilities of the ligands, in good correlation with their reported biological activities. It was 3-fluorosalicylic acid, which formed the most stable complexes [CuLH -1] and [CuL2H-2]2-, while the mononuclear complexes with 6-fluorosalicylic acid were found to be the least stable. For the other ligands (including 5-fluorosalicylic acid studied recently), complexes of medium stabilities were formed. For the interpretation of these findings, ab initio and semi-empirical quantum chemical calculations were carried out for the ligand molecules, isolated and surrounded by water molecules, respectively.

Original languageEnglish
Pages (from-to)75-83
Number of pages9
JournalJournal of Inorganic Biochemistry
Volume105
Issue number1
DOIs
Publication statusPublished - Jan 2011

Fingerprint

Fluorine
Ligands
Paramagnetic resonance
Acids
Potentiometry
Molecules
Water
Spectrophotometry
Bioactivity
Complexation
Isomers
Dimers
Methanol
Copper
Atoms

Keywords

  • Coordination modes
  • Copper(II) complexes
  • Electron spin resonance
  • Fluorosalicylic acids
  • Speciation

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

Cite this

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title = "Effect of fluorine position on the coordinating ability of fluorosalicylic acids - An experimental study complemented with computations",
abstract = "The complexation of 3-, 4-, and 6-fluorosalicylic acids (HL) with copper(II) was investigated in aqueous solution by pH-potentiometry combined with UV-visible spectrophotometry, and in 50 v/v {\%} water-methanol mixture by the two-dimensional ESR simulation method. Both methods showed the formation of [CuLH-1] and [CuL2H-2]2- of high stabilities, and, at low excess of ligand, the ESR-silent mixed hydroxido complex [Cu2L2H-3]-. Further species were also identified by the two-dimensional ESR simulation method: [CuL] + in the acidic region, the minor dimer [Cu2L 2H-2], and the cis and the trans isomers for [CuL 2H-2]2-. The position of the fluorine atom in the aromatic ring had significant effect on the coordination abilities of the ligands, in good correlation with their reported biological activities. It was 3-fluorosalicylic acid, which formed the most stable complexes [CuLH -1] and [CuL2H-2]2-, while the mononuclear complexes with 6-fluorosalicylic acid were found to be the least stable. For the other ligands (including 5-fluorosalicylic acid studied recently), complexes of medium stabilities were formed. For the interpretation of these findings, ab initio and semi-empirical quantum chemical calculations were carried out for the ligand molecules, isolated and surrounded by water molecules, respectively.",
keywords = "Coordination modes, Copper(II) complexes, Electron spin resonance, Fluorosalicylic acids, Speciation",
author = "T. Szab{\'o}-Pl{\'a}nka and B. Gyurcsik and I. P{\'a}link{\'o} and N. Nagy and A. Rockenbauer and Rastislav Š{\'i}poš and Jozef Šima and Milan Meln{\'i}k",
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TY - JOUR

T1 - Effect of fluorine position on the coordinating ability of fluorosalicylic acids - An experimental study complemented with computations

AU - Szabó-Plánka, T.

AU - Gyurcsik, B.

AU - Pálinkó, I.

AU - Nagy, N.

AU - Rockenbauer, A.

AU - Šípoš, Rastislav

AU - Šima, Jozef

AU - Melník, Milan

PY - 2011/1

Y1 - 2011/1

N2 - The complexation of 3-, 4-, and 6-fluorosalicylic acids (HL) with copper(II) was investigated in aqueous solution by pH-potentiometry combined with UV-visible spectrophotometry, and in 50 v/v % water-methanol mixture by the two-dimensional ESR simulation method. Both methods showed the formation of [CuLH-1] and [CuL2H-2]2- of high stabilities, and, at low excess of ligand, the ESR-silent mixed hydroxido complex [Cu2L2H-3]-. Further species were also identified by the two-dimensional ESR simulation method: [CuL] + in the acidic region, the minor dimer [Cu2L 2H-2], and the cis and the trans isomers for [CuL 2H-2]2-. The position of the fluorine atom in the aromatic ring had significant effect on the coordination abilities of the ligands, in good correlation with their reported biological activities. It was 3-fluorosalicylic acid, which formed the most stable complexes [CuLH -1] and [CuL2H-2]2-, while the mononuclear complexes with 6-fluorosalicylic acid were found to be the least stable. For the other ligands (including 5-fluorosalicylic acid studied recently), complexes of medium stabilities were formed. For the interpretation of these findings, ab initio and semi-empirical quantum chemical calculations were carried out for the ligand molecules, isolated and surrounded by water molecules, respectively.

AB - The complexation of 3-, 4-, and 6-fluorosalicylic acids (HL) with copper(II) was investigated in aqueous solution by pH-potentiometry combined with UV-visible spectrophotometry, and in 50 v/v % water-methanol mixture by the two-dimensional ESR simulation method. Both methods showed the formation of [CuLH-1] and [CuL2H-2]2- of high stabilities, and, at low excess of ligand, the ESR-silent mixed hydroxido complex [Cu2L2H-3]-. Further species were also identified by the two-dimensional ESR simulation method: [CuL] + in the acidic region, the minor dimer [Cu2L 2H-2], and the cis and the trans isomers for [CuL 2H-2]2-. The position of the fluorine atom in the aromatic ring had significant effect on the coordination abilities of the ligands, in good correlation with their reported biological activities. It was 3-fluorosalicylic acid, which formed the most stable complexes [CuLH -1] and [CuL2H-2]2-, while the mononuclear complexes with 6-fluorosalicylic acid were found to be the least stable. For the other ligands (including 5-fluorosalicylic acid studied recently), complexes of medium stabilities were formed. For the interpretation of these findings, ab initio and semi-empirical quantum chemical calculations were carried out for the ligand molecules, isolated and surrounded by water molecules, respectively.

KW - Coordination modes

KW - Copper(II) complexes

KW - Electron spin resonance

KW - Fluorosalicylic acids

KW - Speciation

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U2 - 10.1016/j.jinorgbio.2010.09.009

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JO - Journal of Inorganic Biochemistry

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