Equilibrium and dissociation kinetics of the [Al(NOTA)] complex (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetate)

Edit Farkas, Tamás Fodor, Ferenc K. Kálmán, G. Tircsó, Imre Tóth

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A detailed investigation of the equilibria and dissociation kinetics for the [Al(NOTA)] complex has been carried out. This complex and its derivatives are known as very good carriers for 18F-isotope in positron emission tomography. The thermodynamic stability of [Al(NOTA)] has been studied by “out of cell” pH-potentiometric technique since the formation rate of the complex is very low in acidic medium. 1H- and 27Al-NMR spectra have been recorded to check the time course of equilibration and to validate the equilibrium model consisting of [Al(NOTA)] with lgK = 17.9(1) and [Al(HNOTA)]+ with lgKH = 1.9(3). A metastable mixed hydroxido complex [Al(NOTA)(OH)] with lgKAl(NOTA)OH= −12.2(1) was detected in alkaline solution by direct pH-potentiometry, which transforms slowly to [Al(OH)4]. The decomplexation reactions of [Al(NOTA)] have been investigated in both acidic and basic conditions. The rate of dissociation is extremely low in acidic medium, while in alkaline solution, it can be characterized by the rate law kobs = k0 + k1[OH], where k0 = (2.0 ± 0.1) × 10−6 s−1 and k1 = (6.8 ± 0.5) × 10−6 M−1s−1. The formation of the ternary [Al(NOTA)(F)] complex via direct reaction of [Al(NOTA)] and F cannot be detected by either fluoride selective electrode or by 19F-NMR spectroscopy. However, by applying solvent mixture (1:1 ethanol:water) and heating, the ternary [Al(NOTA)(F)] complex was found to form quantitatively within 15 minutes.

Original languageEnglish
JournalReaction Kinetics, Mechanisms and Catalysis
DOIs
Publication statusAccepted/In press - Jun 13 2015

Fingerprint

dissociation
Positron emission tomography
Kinetics
kinetics
Nuclear magnetic resonance spectroscopy
Isotopes
potentiometric analysis
nuclear magnetic resonance
Thermodynamic stability
Ethanol
Nuclear magnetic resonance
Derivatives
Heating
Electrodes
fluorides
positrons
ethyl alcohol
isotopes
tomography
Water

Keywords

  • <sup>19</sup>F-NMR
  • <sup>27</sup>Al-NMR
  • Aluminium-NOTA
  • Kinetic inertness
  • PET
  • Ternary complex
  • Thermodynamic stability

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

Cite this

Equilibrium and dissociation kinetics of the [Al(NOTA)] complex (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetate). / Farkas, Edit; Fodor, Tamás; Kálmán, Ferenc K.; Tircsó, G.; Tóth, Imre.

In: Reaction Kinetics, Mechanisms and Catalysis, 13.06.2015.

Research output: Contribution to journalArticle

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title = "Equilibrium and dissociation kinetics of the [Al(NOTA)] complex (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetate)",
abstract = "A detailed investigation of the equilibria and dissociation kinetics for the [Al(NOTA)] complex has been carried out. This complex and its derivatives are known as very good carriers for 18F-isotope in positron emission tomography. The thermodynamic stability of [Al(NOTA)] has been studied by “out of cell” pH-potentiometric technique since the formation rate of the complex is very low in acidic medium. 1H- and 27Al-NMR spectra have been recorded to check the time course of equilibration and to validate the equilibrium model consisting of [Al(NOTA)] with lgK = 17.9(1) and [Al(HNOTA)]+ with lgKH = 1.9(3). A metastable mixed hydroxido complex [Al(NOTA)(OH)]− with lgKAl(NOTA)OH= −12.2(1) was detected in alkaline solution by direct pH-potentiometry, which transforms slowly to [Al(OH)4]−. The decomplexation reactions of [Al(NOTA)] have been investigated in both acidic and basic conditions. The rate of dissociation is extremely low in acidic medium, while in alkaline solution, it can be characterized by the rate law kobs = k0 + k1[OH−], where k0 = (2.0 ± 0.1) × 10−6 s−1 and k1 = (6.8 ± 0.5) × 10−6 M−1s−1. The formation of the ternary [Al(NOTA)(F)]− complex via direct reaction of [Al(NOTA)] and F− cannot be detected by either fluoride selective electrode or by 19F-NMR spectroscopy. However, by applying solvent mixture (1:1 ethanol:water) and heating, the ternary [Al(NOTA)(F)]– complex was found to form quantitatively within 15 minutes.",
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T1 - Equilibrium and dissociation kinetics of the [Al(NOTA)] complex (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetate)

AU - Farkas, Edit

AU - Fodor, Tamás

AU - Kálmán, Ferenc K.

AU - Tircsó, G.

AU - Tóth, Imre

PY - 2015/6/13

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N2 - A detailed investigation of the equilibria and dissociation kinetics for the [Al(NOTA)] complex has been carried out. This complex and its derivatives are known as very good carriers for 18F-isotope in positron emission tomography. The thermodynamic stability of [Al(NOTA)] has been studied by “out of cell” pH-potentiometric technique since the formation rate of the complex is very low in acidic medium. 1H- and 27Al-NMR spectra have been recorded to check the time course of equilibration and to validate the equilibrium model consisting of [Al(NOTA)] with lgK = 17.9(1) and [Al(HNOTA)]+ with lgKH = 1.9(3). A metastable mixed hydroxido complex [Al(NOTA)(OH)]− with lgKAl(NOTA)OH= −12.2(1) was detected in alkaline solution by direct pH-potentiometry, which transforms slowly to [Al(OH)4]−. The decomplexation reactions of [Al(NOTA)] have been investigated in both acidic and basic conditions. The rate of dissociation is extremely low in acidic medium, while in alkaline solution, it can be characterized by the rate law kobs = k0 + k1[OH−], where k0 = (2.0 ± 0.1) × 10−6 s−1 and k1 = (6.8 ± 0.5) × 10−6 M−1s−1. The formation of the ternary [Al(NOTA)(F)]− complex via direct reaction of [Al(NOTA)] and F− cannot be detected by either fluoride selective electrode or by 19F-NMR spectroscopy. However, by applying solvent mixture (1:1 ethanol:water) and heating, the ternary [Al(NOTA)(F)]– complex was found to form quantitatively within 15 minutes.

AB - A detailed investigation of the equilibria and dissociation kinetics for the [Al(NOTA)] complex has been carried out. This complex and its derivatives are known as very good carriers for 18F-isotope in positron emission tomography. The thermodynamic stability of [Al(NOTA)] has been studied by “out of cell” pH-potentiometric technique since the formation rate of the complex is very low in acidic medium. 1H- and 27Al-NMR spectra have been recorded to check the time course of equilibration and to validate the equilibrium model consisting of [Al(NOTA)] with lgK = 17.9(1) and [Al(HNOTA)]+ with lgKH = 1.9(3). A metastable mixed hydroxido complex [Al(NOTA)(OH)]− with lgKAl(NOTA)OH= −12.2(1) was detected in alkaline solution by direct pH-potentiometry, which transforms slowly to [Al(OH)4]−. The decomplexation reactions of [Al(NOTA)] have been investigated in both acidic and basic conditions. The rate of dissociation is extremely low in acidic medium, while in alkaline solution, it can be characterized by the rate law kobs = k0 + k1[OH−], where k0 = (2.0 ± 0.1) × 10−6 s−1 and k1 = (6.8 ± 0.5) × 10−6 M−1s−1. The formation of the ternary [Al(NOTA)(F)]− complex via direct reaction of [Al(NOTA)] and F− cannot be detected by either fluoride selective electrode or by 19F-NMR spectroscopy. However, by applying solvent mixture (1:1 ethanol:water) and heating, the ternary [Al(NOTA)(F)]– complex was found to form quantitatively within 15 minutes.

KW - <sup>19</sup>F-NMR

KW - <sup>27</sup>Al-NMR

KW - Aluminium-NOTA

KW - Kinetic inertness

KW - PET

KW - Ternary complex

KW - Thermodynamic stability

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