Synthesis and dynamic properties of kinetically inert lanthanide compounds: Lanthanum(III) and Europium(III) complexes of 1,4,7,10-tetrakis(2-hydroxyethyl)-1,4,7,10-tetraazacyclododecane

Journal Article · Wed Jul 21 04:00:00 EDT 1993 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00067a028· OSTI ID:5548539

Morrow, J R; Aileen Chin, K O ^[1]

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1. State Univ. of New York, Buffalo (United States)

The synthesis and dynamic properties of La(THED)(CF[sub 3]SO[sub 3])[sub 3] and Eu(THED)(CF[sub 3]SO[sub 3])[sub 3] are described. (THED is 1,47,10-tetrakis(2-hydroxyethyl)-1,4,7,10-tetraazacyclododecane.) Variable-temperature [sup 1]H and [sup 13]C NMR studies indicate that the ethylenic groups of the 12-membered tetraaza macrocycle are rigid on the NMR time scale at low temperatures (-40[degrees]C), and all adopt the same conformation. Macrocycle rigidity is lost at elevated temperatures. A dynamic process involving conformational changes of the ethylenic groups in the tetraazamacrocycle is consistent with NMR data. An energy barrier of 52 ([plus minus]0.7) kJ mol[sup [minus]1] is calculated for this process from line-shape analysis of [sup 13]C NMR spectra of La(THED)(CF[sub 3]SO[sub 3])[sub 3] at four temperatures. Both complexes are stable in water at near-neutral pH. The dissociation of La[sup 3+] or Eu[sup 3+] from their respective complexes is investigated in the presence of excess Cu[sup 2+] by monitoring an absorbance at 312 nm attributed to the Cu(THED)[sup 2+] complex. For La(THED)(CF[sub 3]SO[sub 3])[sub 3], dissociation is first-order in lanthanum complex and independent of Cu[sup 2+] with a first-order rate constant of 9.2 ([plus minus]0.5) x 10[sup [minus]6] s[sup [minus]1] at 37 [degrees]C, pH 6.0. Eu(THED)(CF[sub 3]SO[sub 3])[sub 3] is substantially more inert to metal ion release than is the lanthanum complex. The first-order rate constant for dissociation of the europium complex at pH 6.0 and 37 [degrees]C is 7.1 ([plus minus]0.4) x 10[sup [minus]7] s[sup [minus]1]; there is a slight dependence of the rate constant on pH in the pH range 3.0-6.8.

• OSTI ID: 5548539
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 32:15; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AZINES
CARBON 13
CARBON ISOTOPES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
COMPLEXES
CONFORMATIONAL CHANGES
COPPER COMPLEXES
DISSOCIATION
EUROPIUM COMPLEXES
EVEN-ODD NUCLEI
HETEROCYCLIC COMPOUNDS
ISOTOPES
KINETICS
LANTHANUM COMPLEXES
LIGHT NUCLEI
MAGNETIC RESONANCE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
RARE EARTH COMPLEXES
REACTION KINETICS
RESONANCE
SPECTRA
SPECTROPHOTOMETRY
STABLE ISOTOPES
SYNTHESIS
TRANSITION ELEMENT COMPLEXES