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Titolo:
Nuclear and electronic relaxation of Eu-(aq)(2+): An extremely labile aquaion
Autore:
Caravan, P; Toth, E; Rockenbauer, A; Merbach, AE;
Indirizzi:
Univ Lausanne, Inst Inorgan & Analyt Chem, BCH, CH-1015 Lausanne, Switzerland Univ Lausanne Lausanne Switzerland CH-1015 CH-1015 Lausanne, Switzerland Chem Res Ctr, Inst Chem, Budapest, Hungary Chem Res Ctr Budapest Hungary hem Res Ctr, Inst Chem, Budapest, Hungary Tech Univ Budapest, Dept Expt Phys, Budapest, Hungary Tech Univ Budapest Budapest Hungary , Dept Expt Phys, Budapest, Hungary
Titolo Testata:
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
fascicolo: 44, volume: 121, anno: 1999,
pagine: 10403 - 10409
SICI:
0002-7863(19991110)121:44<10403:NAEROE>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELASTIC NEUTRON-SCATTERING; WATER EXCHANGE-RATE; MAGNETIC-RESONANCE; AQUEOUS-SOLUTIONS; O-17 NMR; SPIN RELAXATION; CONTRAST AGENTS; COMPLEXES; DYNAMICS; PRESSURE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
42
Recensione:
Indirizzi per estratti:
Indirizzo: Merbach, AE Univ Lausanne, Inst Inorgan & Analyt Chem, BCH, CH-1015 Lausanne, Switzerland Univ Lausanne Lausanne Switzerland CH-1015 anne, Switzerland
Citazione:
P. Caravan et al., "Nuclear and electronic relaxation of Eu-(aq)(2+): An extremely labile aquaion", J AM CHEM S, 121(44), 1999, pp. 10403-10409

Abstract

Variable-temperature (at 4.7 and 9.4 T) and variable-pressure (9.4 T) O-17nuclear relaxation rates were measured for the Eu(TI) aqua ion. Variable-temperature H-1 nuclear magnetic relaxation dispersion(NMRD) profiles were recorded. In addition, EPR spectra of the Eu(II) aqua ion are reported as a function of temperature at 0.34, 2.7, 5.4, and 8.1 T. The simultaneous fit of the nuclear and electronic relaxation rate data results in k(ex)(298) = 4.4 x 10(9) s(-1) for the water exchange rate with activation parameters Delta H-double dagger = 15.7 kJ mol(-1) and Delta S-double dagger = -7.0 J K-1 mol(-1), Delta V-double dagger = -11.3 cm(3) mol(-1) for the volume of activation for exchange, and tau(R)(298) = 16.3 ps for the rotational correlation time. Water exchange at Eu-(aq)(2+) occurs via an associative mechanism and has the highest rate ever measured at an aqua ion by magnetic resonance.:The high-field EPR spectra, reported here for the first time for divalent Eu, show hyperfine coupling to Eu-151 and Eu-153 and the coupling constants are determined (37.3 and 16.4 G for Eu-151 and Eu-153, respectively). The electronic relaxation times, T-1e and T-2e, are longer than for the isoelectronic Gd(III) aqua ion. The implications of these results for ligand exchange at Ca(II) and for magnetic resonance imaging contrast agents are discussed.

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Documento generato il 11/07/20 alle ore 20:07:22