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Titolo:
MULTINUCLEAR MAGNETIC-RESONANCE STUDY OF THE STRUCTURE AND DYNAMICS OF LANTHANIDE(III) COMPLEXES OF THE BIS(PROPYLAMIDE) OF DIETHYLENETRIAMINEPENTAACETIC ACID IN AQUEOUS-SOLUTION
Autore:
GERALDES CFGC; URBANO AM; HOEFNAGEL MA; PETERS JA;
Indirizzi:
UNIV COIMBRA,DEPT BIOCHEM P-3000 COIMBRA PORTUGAL DELFT UNIV TECHNOL,ORGAN CHEM & CATALYSIS LAB 2628 BL DELFT NETHERLANDS
Titolo Testata:
Inorganic chemistry
fascicolo: 11, volume: 32, anno: 1993,
pagine: 2426 - 2432
SICI:
0020-1669(1993)32:11<2426:MMSOTS>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
O-17 NMR SHIFTS; CONTRAST AGENTS; CHEMICAL EXCHANGE; RELAXATION-TIMES; CATIONS; COORDINATION; SEPARATION; HYDRATION; REAGENTS; SYSTEMS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
52
Recensione:
Indirizzi per estratti:
Citazione:
C.F.G.C. Geraldes et al., "MULTINUCLEAR MAGNETIC-RESONANCE STUDY OF THE STRUCTURE AND DYNAMICS OF LANTHANIDE(III) COMPLEXES OF THE BIS(PROPYLAMIDE) OF DIETHYLENETRIAMINEPENTAACETIC ACID IN AQUEOUS-SOLUTION", Inorganic chemistry, 32(11), 1993, pp. 2426-2432

Abstract

The structure and dynamics of the lanthanide(III) complexes of the bis(propylamide) of diethylenetriaminepentaacetate (DTPA-PA2) in aqueoussolution have been investigated by C-13 and O-17 NMR. With the use ofthe longitudinal C-13 relaxation times of the Nd(III) complex it is shown that the organic ligand is bound to the lanthanide(III) ion in anoctadentate fashion via the three nitrogens of the diethylenetriaminebackbone, the three carboxylate groups, and the two amide oxygens. O-17 NMR measurements show that the coordination sphere is completed by one water ligand. The inversion of the lanthanide-bound nitrogens is precluded, and therefore four diastereomeric pairs of isomers are possible for these complexes. Low-temperature C-13 NMR spectra show that all these isomers occur in solution. Three dynamic processes have been identified by means of variable-temperature NMR measurements: (i) rapidrotations of the carboxylate groups, (ii) racemization at the middle N atom via interconversions between the two possible conformations of the ethylene bridges, and (iii) racemization at the terminal N atoms of the diethylenetriamine backbone via decoordination-inversion-coordination. The barriers of the interconversions between the enantiomers have been determined by line-shape analysis and from coalescence temperatures. A comparison is made with the Ln(III) diethylenetriaminepentaacetate (DTPA) complexes.

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Documento generato il 28/11/20 alle ore 09:56:48