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Titolo:
NMR CONFORMATIONAL STUDY OF DIAMAGNETIC COMPLEXES OF SOME TRIAZATRIACETATE MACROCYCLES
Autore:
GERALDES CFGC; MARQUES MPM; SHERRY AD;
Indirizzi:
UNIV COIMBRA,FAC SCI & TECHNOL,DEPT BIOCHEM,APARTADO 3126 P-3000 COIMBRA PORTUGAL UNIV COIMBRA,FAC SCI & TECHNOL,CTR NEUROSCI P-3000 COIMBRA PORTUGAL UNIV TEXAS,DEPT CHEM RICHARDSON TX 75083 UNIV TEXAS,SW MED CTR,DEPT RADIOL,ROGERS MAGNET RESONANCE CTR DALLAS TX 75235
Titolo Testata:
Inorganica Chimica Acta
fascicolo: 1-2, volume: 273, anno: 1998,
pagine: 288 - 298
SICI:
0020-1693(1998)273:1-2<288:NCSODC>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEAR MAGNETIC-RESONANCE; METAL-ION COMPLEXES; MOLECULAR-STRUCTURE; CRYSTAL-STRUCTURES; AQUEOUS-SOLUTION; ACID; LIGANDS; DESIGN; GADOLINIUM(III); STABILITIES;
Keywords:
NMR STUDY; ALKALINE COMPLEXES; ALKALINE-EARTH COMPLEXES; TRIAZAACETATE MACROCYCLE COMPLEXES; DIAMAGNETIC COMPLEXES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
46
Recensione:
Indirizzi per estratti:
Citazione:
C.F.G.C. Geraldes et al., "NMR CONFORMATIONAL STUDY OF DIAMAGNETIC COMPLEXES OF SOME TRIAZATRIACETATE MACROCYCLES", Inorganica Chimica Acta, 273(1-2), 1998, pp. 288-298

Abstract

The conformational properties of the diamagnetic complexes formed by five triazatriacetic macrocyclic ligands with monovalent (alkaline) and divalent (alkaline-earth, Zn2+ and Cd2+) cations have been studied by proton nuclear magnetic resonance spectroscopy (H-1 NMR) in aqueous solution as a function of pH and temperature. These structurally related triazatriacetic ligands, 1,4,7-triazacyclononane-N,N',N ''-triacetic acid (NOTA), 1,4,7-triazacyclodecane-N,N',N ''-triacetic acid (DETA), 1,4,8-triazacycloundecane-N,N',N ''-triacetic acid (UNTA), 1,5,9-triazacyclododecane-N,N',N ''-triacetic acid (DOTRA), and 9,10-benzylidene-1,4,7-triazacyclotridecane-N,N',N ''-triacetic acid, (BUNTA) have triazamacrocyclic rings with different sizes and flexibilities, bearing three pendant acetate arms. In the case of the alkaline-earth, Zn2+ and Cd2+ cations, only one complex form (1:1) has been detected for all the ligands studied. In most cases the metal ion is coordinated to allthe ligand ring nitrogens and to all or some of the carboxylate groups of the pendant arms, except when a poor fit of the cations into the macrocyclic hole occurs, such as for the Ba2+ complexes of DETA, UNTA and DOTRA and the Ca2+ and Sr2+ complexes of BUNTA. The resonance patterns of the ring proton resonances, determined by the long lifetime ofthe metal-nitrogen bonds, indicate that the six-membered rings formedupon chelation are conformationally rigid and the five-membered ringsare conformationally flexible. The multiplicity of the acetate protonresonances shows that the metal-oxygen bonds are long-lived or short lived depending whether the acetates are bound to nitrogens involved in two ring bridges of equal or unequal sizes. (C) 1998 Elsevier Science S.A. All rights reserved.

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Documento generato il 12/07/20 alle ore 03:07:42