TREN-HOPO

Apromising new class of stable Gd3+ complexes based onTREN-Me- 3,2 -HOPO shows relatively fast water exchange rates. The water soluble tris(2-hydroxymethyl)-TREN-Me-3,2-HOPO complex is eight-coordinate with two water molecules in the first coordination sphere (234). The water exchange rate is more than one order of magnitude faster than on DTPA and DOTA complexes and the mechanism is proposed to be a-activated. 

Fig. 4. Capping units (a) bonding through peptide links, (b) to ring-carbon or ring-nitrogen, (c) to give hexadentate hydroxypyridinones, (d) such as 21, tren(3,2-hopo)3.

Fig. 6. (a) (b) Replacement of a peptide-bound l-hydroxy-2-pyridinone unit by a catechol unit on a tris(ammoethyl)aniine (tren) cap. (c) A tren-capped hexadentate ligand with two 3-hydroxy-2-pyridinone (3,2-hopo) and one terephthalamide (tarn) chelating units. 

The first report of the preparation and characterization of a tripodal hexadentate ligand complex of Gd, that of tren-Me-3,2-hopo (25 in... 

Attaching cyclic, bidentate 1-hydroxy-177-pyridin-2-thione, 1-hydroxy-177-pyridin-2-one (1,2-HOPO) and 2-hydroxy-277-isoquinolin-l-one (1,2-HOIQO) ligating units via their C-6 carbon to TREN template produced 19 , 20 and 21 , respectively. 

Figure 46.1 Schematic structure of some ligand cages used to prepare highly sensitive gadohnium-based contrast agent with q = 2. (a) PCTA-[12], (b) D03A, (c) AAZTA, and (d) TREN-l-Me-3,2-HOPO.

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