Research article summary (published 10 Jun 2008):

Triethylenetetramine penta- and hexa-acetamide ligands and their ytterbium complexes as paraCEST contrast agents for MRI.

Full Abstract

The ligand triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetamide (ttham) was synthesized with the aim of forming lanthanide complexes suitable as contrast agents for magnetic resonance imaging applications utilizing the chemical exchange-dependent saturation transfer (CEST) effect. It was designed to exclude water molecules from the first coordination sphere and provide a high number of CEST active amide protons per lanthanide ion. The ligand was characterized by its protonation behavior and its complexation properties with ytterbium ions in aqueous solution. The basicity of the ttham backbone amine protons decreases in the order N(central(1)) > N(terminal(1)) > N(terminal(2)) > N(central(2)), as deduced from NMR titration experiments and from a comparison of its protonation constants with those of two ttham derivatives, in which either a terminal (N-benzyl-triethylenetetramine-N,N',N'',N''',N'''-pentaacetamide, 1bttpam) or a central acetamide group (N'-benzyl-triethylenetetramine-N,N,N'',N''',N'''-pentaacetamide, 4bttpam) is substituted with a benzyl group. This protonation sequence results from the combined influence of inductive effects, the intramolecular hydrogen bonding network, and the Coulomb repulsion between protonated ammonium groups. The ytterbium complex of ttham, [Yb(ttham)]Cl(3), is coordinatively frustrated. Due to steric constraints, in addition to the four backbone nitrogen atoms, only three of the four symmetry-equivalent terminal acetamide donors can coordinate simultaneously to the ytterbium ion, and the dangling fourth one exchanges quickly with the other three. The ytterbium complexes of a total of five ligands (ttham, 1bttpam, 4bttpam, 2,2',2''-triaminotriethylaminehexaacetamide (ttaham), and diethylenetriamine-N,N,N',N'',N''-pentaacetamide (dtpam)) were studied with respect to their CEST properties. In solution, all of these complexes have a low symmetry. The presence of multiple magnetically different amide groups in each complex prevents the realization of very high CEST effects. These results nevertheless form an excellent basis for a further optimization of this class of ligands.

Author information

Author/s: Burdinski, Dirk (D); Lub, Johan (J); Pikkemaat, Jeroen A (JA); Moreno Jalón, Diana (D); Martial, Sophie (S); Del Pozo Ochoa, Carolina (C);

Affiliation: Department of Bio-Molecular Engineering, Philips Research, High Tech Campus, 5656 AE, Eindhoven, The Netherlands. dirk.burdinski(-atsign-)philips.com

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Dalton transactions (Cambridge, England : 2003) (Dalton Trans), published in England. (Language: eng)

Reference: 2008-Aug; vol (issue 31) : pp 4138-51

Dates: Created 2008/08/08; Completed 2009/09/25;

PMID: 18688432, status: MEDLINE (last retrieval date: 9/25/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

Comments and Corrections

ErratumIn: Dalton Trans. 2008 Dec 28;(48):7037.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Acetamides - chemistry Benzene - chemistry Contrast Media - chemical synthesis; chemistry; diagnostic use Ligands Magnetic Resonance Imaging

Magnetic Resonance Spectroscopy Organometallic Compounds - chemical synthesis; chemistry; diagnostic use Protons Triethylenetetramine - chemistry Ytterbium - chemistry

Associated Chemicals: Acetamides (0) ; Contrast Media (0) ; Ligands (0) ; Organometallic Compounds (0) ; Protons (0) ; Triethylenetetramine (112-24-3) ; acetamide (60-35-5) ; Benzene (71-43-2) ; Ytterbium (7440-64-4)

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