Aminopolycarboxylates of rare earths. 13. The apparent molal volumes of the lanthanide(III), cobalt(III) and chromium(III) ethylenediamine tetraacetate complexes

E. Brücher, Cs E. Kukri, R. Király

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Abstract

The apparent molal volumes of the complexes KLnedta (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb), KCoedta and KCredta were determined from density measurements. The apparent molal volumes of the complexes KLnedta show a non-monotonous change with increasing atomic number; there is a significant increase in the values between Nd and Gd. To explain the observed trend, a structural change is postulated to take place gradually on progressing from Gd towards La. With increasing ionic size, there is an increase in the metal-ligand bond distances and in the mobility of the functional groups, resulting in a jump in the number of coordinated water molecules by one between Gd and Nd. There is a further increase in the hydration of the central ions, connected with the gradual de-coordination of a carboxylate group. As a result of the gradual structural change there is one free carboxylate group on average in Laedta- and about four water molecules are coordinated in the inner sphere, while in the complexes of the elements heavier than Gd the ligand is hexadentate and only two water molecules are in the inner sphere. The apparent molal volumes of KCoedta and KCredta are practically equal and are higher than those of the lanthanide complexes; this has been explained by the stronger hydration and the more significant water-ordering effect of the Ln3+ ions coordinated in the complexes Lnedta-. The postulated structural changes correlate with the trend of the protonation constant values, as well as with the results of 1H NMR studies on the complexes Lnedta-.

Original languageEnglish
Pages (from-to)135-139
Number of pages5
JournalInorganica Chimica Acta
Volume95
Issue number3
DOIs
Publication statusPublished - 1984

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ethylenediamine
Lanthanoid Series Elements
Chromium
Cobalt
Rare earth elements
Rare earths
chromium
cobalt
rare earth elements
Water
Hydration
water
carboxylates
Molecules
hydration
Ligands
Ions
trends
molecules
ligands

ASJC Scopus subject areas

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

Cite this

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title = "Aminopolycarboxylates of rare earths. 13. The apparent molal volumes of the lanthanide(III), cobalt(III) and chromium(III) ethylenediamine tetraacetate complexes",
abstract = "The apparent molal volumes of the complexes KLnedta (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb), KCoedta and KCredta were determined from density measurements. The apparent molal volumes of the complexes KLnedta show a non-monotonous change with increasing atomic number; there is a significant increase in the values between Nd and Gd. To explain the observed trend, a structural change is postulated to take place gradually on progressing from Gd towards La. With increasing ionic size, there is an increase in the metal-ligand bond distances and in the mobility of the functional groups, resulting in a jump in the number of coordinated water molecules by one between Gd and Nd. There is a further increase in the hydration of the central ions, connected with the gradual de-coordination of a carboxylate group. As a result of the gradual structural change there is one free carboxylate group on average in Laedta- and about four water molecules are coordinated in the inner sphere, while in the complexes of the elements heavier than Gd the ligand is hexadentate and only two water molecules are in the inner sphere. The apparent molal volumes of KCoedta and KCredta are practically equal and are higher than those of the lanthanide complexes; this has been explained by the stronger hydration and the more significant water-ordering effect of the Ln3+ ions coordinated in the complexes Lnedta-. The postulated structural changes correlate with the trend of the protonation constant values, as well as with the results of 1H NMR studies on the complexes Lnedta-.",
author = "E. Br{\"u}cher and Kukri, {Cs E.} and R. Kir{\'a}ly",
year = "1984",
doi = "10.1016/S0020-1693(00)87609-4",
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journal = "Inorganica Chimica Acta",
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T1 - Aminopolycarboxylates of rare earths. 13. The apparent molal volumes of the lanthanide(III), cobalt(III) and chromium(III) ethylenediamine tetraacetate complexes

AU - Brücher, E.

AU - Kukri, Cs E.

AU - Király, R.

PY - 1984

Y1 - 1984

N2 - The apparent molal volumes of the complexes KLnedta (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb), KCoedta and KCredta were determined from density measurements. The apparent molal volumes of the complexes KLnedta show a non-monotonous change with increasing atomic number; there is a significant increase in the values between Nd and Gd. To explain the observed trend, a structural change is postulated to take place gradually on progressing from Gd towards La. With increasing ionic size, there is an increase in the metal-ligand bond distances and in the mobility of the functional groups, resulting in a jump in the number of coordinated water molecules by one between Gd and Nd. There is a further increase in the hydration of the central ions, connected with the gradual de-coordination of a carboxylate group. As a result of the gradual structural change there is one free carboxylate group on average in Laedta- and about four water molecules are coordinated in the inner sphere, while in the complexes of the elements heavier than Gd the ligand is hexadentate and only two water molecules are in the inner sphere. The apparent molal volumes of KCoedta and KCredta are practically equal and are higher than those of the lanthanide complexes; this has been explained by the stronger hydration and the more significant water-ordering effect of the Ln3+ ions coordinated in the complexes Lnedta-. The postulated structural changes correlate with the trend of the protonation constant values, as well as with the results of 1H NMR studies on the complexes Lnedta-.

AB - The apparent molal volumes of the complexes KLnedta (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb), KCoedta and KCredta were determined from density measurements. The apparent molal volumes of the complexes KLnedta show a non-monotonous change with increasing atomic number; there is a significant increase in the values between Nd and Gd. To explain the observed trend, a structural change is postulated to take place gradually on progressing from Gd towards La. With increasing ionic size, there is an increase in the metal-ligand bond distances and in the mobility of the functional groups, resulting in a jump in the number of coordinated water molecules by one between Gd and Nd. There is a further increase in the hydration of the central ions, connected with the gradual de-coordination of a carboxylate group. As a result of the gradual structural change there is one free carboxylate group on average in Laedta- and about four water molecules are coordinated in the inner sphere, while in the complexes of the elements heavier than Gd the ligand is hexadentate and only two water molecules are in the inner sphere. The apparent molal volumes of KCoedta and KCredta are practically equal and are higher than those of the lanthanide complexes; this has been explained by the stronger hydration and the more significant water-ordering effect of the Ln3+ ions coordinated in the complexes Lnedta-. The postulated structural changes correlate with the trend of the protonation constant values, as well as with the results of 1H NMR studies on the complexes Lnedta-.

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