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Modulation of the Lifetime of Water Bound to Lanthanide Metal Ions in Complexes with Ligands Derived from 1,4,7,10‐Tetraazacyclododecane Tetraacetate (DOTA)
Author(s) -
Zhang Shanrong,
Jiang Xiuyan,
Sherry A. Dean
Publication year - 2005
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200590086
Subject(s) - dota , chemistry , lanthanide , amide , molecule , coordination sphere , crystallography , metal , inner sphere electron transfer , metal ions in aqueous solution , ion , paramagnetism , stereochemistry , chelation , inorganic chemistry , organic chemistry , quantum mechanics , physics
A series of di‐ and tetraamide derivatives of DOTA were synthesized, and their lanthanide(III) complexes were examined by multinuclear 1 H‐, 13 C‐, and 17 O‐NMR spectroscopy, and compared with literature data of similar, known complexes ( Table ). All ligands formed structures similar to the parent [Ln III (DOTA)] − complexes, with four N‐atoms and four O‐atoms from DOTA and one O‐atom from the inner‐sphere water molecules. Interestingly, the lifetimes τ M of the inner‐sphere, metal‐bound water molecules vary widely, ranging from nano‐ to milliseconds, depending on the identity of the pendent amide side chains. In general, positively charged [Ln III (DOTA‐tetraamide)] 3+ complexes display the longest residence times (high τ M values), while complexes with additional charged functional groups on the extended amides display much smaller τ M values, even when the side groups are not directly coordinated to the central Ln 3+ ions. The design of novel [Ln III (DOTA‐tetraamide)] 3+ complexes with a wide, tunable range of τ M values is of prime importance for the application of fast‐responding, paramagnetic chemical‐exchange‐saturation‐transfer (PARACEST) imaging agents used for the study of physiological and metabolic processes.