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A Multinuclear NMR Relaxometry Study of Ternary Adducts Formed between Heptadentate Gd III Chelates and L ‐Lactate
Author(s) -
Terreno Enzo,
Botta Mauro,
Boniforte Patrizia,
Bracco Chiara,
Milone Luciano,
Mondino Bruna,
Uggeri Fulvio,
Aime Silvio
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500129
Subject(s) - chemistry , ternary operation , adduct , relaxation (psychology) , denticity , chelation , nuclear magnetic resonance spectroscopy , ligand (biochemistry) , relaxometry , ternary complex , crystallography , nuclear magnetic resonance , stereochemistry , inorganic chemistry , organic chemistry , magnetic resonance imaging , crystal structure , biochemistry , receptor , spin echo , medicine , psychology , social psychology , enzyme , physics , computer science , radiology , programming language
Dramatic relaxation enhancements of L ‐lactate resonances have been observed upon formation of ternary adducts with Gd III complexes of heptadentate DO3A and DO3A‐like ligands (DO3A=1,4,7,10‐tetraazaciclododecane‐1,4,7‐triacetic acid). Detailed 1 H and 17 O NMR relaxometry investigations allow us to obtain structural, dynamic and thermodynamic information on the ternary complexes in which L ‐lactate acts as a bidentate ligand replacing two water molecules in the inner coordination sphere of the Gd III ion. It has been found that the exchange rate of the coordinated L ‐lactate is modulated by the structural and electronic properties of the parent Gd‐heptacoordinated macrocyclic chelate. In addition to the characterisation of the relaxation behaviour of the 1 H methyl resonance of L ‐lactate, this study has been extended to its 13 C isomer (fully enriched at the three positions) and to the trifluoro‐ L ‐lactate. The obtained results may be relevant to the development of relaxation agents able to promote the relaxation enhancement of specific substrates detectable by in vivo magnetic resonance spectroscopy.