Modulation of the Lifetime of Water Bound to Lanthanide Metal Ions in Complexes with Ligands Derived from 1,4,7,10-Tetraazacyclododecane Tetraacetate (DOTA)

✍ Scribed by Shanrong Zhang; Xiuyan Jiang; A. Dean Sherry

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: German
• Weight: 261 KB
• Volume: 88
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200590086

✦ Synopsis

Abstract

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.