NMR characterization of lanthanide(3+) complexes of tetraazatetrakisphosphinato and tetraazatetrakisphosphonato ligands

Giovannia A. Pereira, Laura Ball, A. Dean Sherry, Joop A. Peters, Carlos F G C Geraldes

Research output: Contribution to journalArticle

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Abstract

The three-dimensional structures in aqueous solution of the entire series of the Ln3+ complexes [Ln(DOTP*-Et)]- (formed from the free ligand P,P′,P″,P‴-[1,4,7,10-tetraazacyclododecane-1, 4,7, 10-tetrayltetrakis(methylene)]tetrakis[P-ethylphosphinic acid] (H 4DOTP*-Et) were studied by NMR techniques to rationalize the parameters governing the relaxivity of the Gd3+ complex and evaluate its potential as MRI contrast agent. From the 1H- and 31P-NMR lanthanide-induced-shift (LIS) values, especially of the [Yb(DOTP*-Et)]- complex, it was concluded that the [Ln(DOTP*-Et)]- complexes adopt in solution twisted square antiprismatic coordination geometries which change gradually their coordination-cage structure along the lanthanide series. These complexes have no inner-sphere-H2O coordination, and preferentially have the (R,R,R,R) configuration of the P-atoms in the pendant arms. Self-association was observed in aqueous solution for the tetraazatetrakisphosphonic acid ester complexes [Ln(DOTP*-OEt)]- (= [Ln(DOTP-Et)]-) and [Ln(DOTP*-OBu)]- (= [Ln(DOTP-Bu)] -) at and above 5 mm concentration, through analysis of 31P-NMR, EPR, vapor-pressure-osmometry, and luminescence-spectroscopic data. The presence of the cationic detergent cetylpyridinium chloride (CPC; but not of neutral surfactants) shifts the isomer equilibrium of [Eu(DOTP*-OBu)]- to the (S,S,S,S) form which selectively binds to the cationic micelle surface.

Original languageEnglish (US)
Pages (from-to)2532-2551
Number of pages20
JournalHelvetica Chimica Acta
Volume92
Issue number11
DOIs
StatePublished - Nov 2009

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Lanthanoid Series Elements
Rare earth elements
Ligands
Nuclear magnetic resonance
nuclear magnetic resonance
ligands
aqueous solutions
acids
Acids
detergents
shift
Detergents
Vapor pressure
methylene
Isomers
Micelles
Magnetic resonance imaging
vapor pressure
Paramagnetic resonance
Luminescence

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Catalysis
  • Drug Discovery
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

NMR characterization of lanthanide(3+) complexes of tetraazatetrakisphosphinato and tetraazatetrakisphosphonato ligands. / Pereira, Giovannia A.; Ball, Laura; Sherry, A. Dean; Peters, Joop A.; Geraldes, Carlos F G C.

In: Helvetica Chimica Acta, Vol. 92, No. 11, 11.2009, p. 2532-2551.

Research output: Contribution to journalArticle

Pereira, Giovannia A. ; Ball, Laura ; Sherry, A. Dean ; Peters, Joop A. ; Geraldes, Carlos F G C. / NMR characterization of lanthanide(3+) complexes of tetraazatetrakisphosphinato and tetraazatetrakisphosphonato ligands. In: Helvetica Chimica Acta. 2009 ; Vol. 92, No. 11. pp. 2532-2551.
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AB - The three-dimensional structures in aqueous solution of the entire series of the Ln3+ complexes [Ln(DOTP*-Et)]- (formed from the free ligand P,P′,P″,P‴-[1,4,7,10-tetraazacyclododecane-1, 4,7, 10-tetrayltetrakis(methylene)]tetrakis[P-ethylphosphinic acid] (H 4DOTP*-Et) were studied by NMR techniques to rationalize the parameters governing the relaxivity of the Gd3+ complex and evaluate its potential as MRI contrast agent. From the 1H- and 31P-NMR lanthanide-induced-shift (LIS) values, especially of the [Yb(DOTP*-Et)]- complex, it was concluded that the [Ln(DOTP*-Et)]- complexes adopt in solution twisted square antiprismatic coordination geometries which change gradually their coordination-cage structure along the lanthanide series. These complexes have no inner-sphere-H2O coordination, and preferentially have the (R,R,R,R) configuration of the P-atoms in the pendant arms. Self-association was observed in aqueous solution for the tetraazatetrakisphosphonic acid ester complexes [Ln(DOTP*-OEt)]- (= [Ln(DOTP-Et)]-) and [Ln(DOTP*-OBu)]- (= [Ln(DOTP-Bu)] -) at and above 5 mm concentration, through analysis of 31P-NMR, EPR, vapor-pressure-osmometry, and luminescence-spectroscopic data. The presence of the cationic detergent cetylpyridinium chloride (CPC; but not of neutral surfactants) shifts the isomer equilibrium of [Eu(DOTP*-OBu)]- to the (S,S,S,S) form which selectively binds to the cationic micelle surface.

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