title: Gadolinium(III) 1,2-hydroxypyridonate-based complexes: toward MRI contrast agents of high relaxivity.
abstract: Prospective gadolinium(III) MRI contrast agent precursors [Gd-TREN-1,2-HOPO] (1) [TREN-1,2-HOPO = tris[(1-hydroxy-2-oxo-1,2-dihydropyridine-6-carboxamido)ethyl]amine] and [Gd-TREN-bis(Me-3,2-HOPO)-1,2-HOPO] (2) have been synthesized and characterized by relaxometric measurements. The water proton relaxivity values of 1 and 2 (20 MHz and 25 degrees C) are 9.5 and 9.3 mM(-)(1)s(-)(1), respectively, suggesting the presence of two coordinated water molecules. The molecular structure of [1.DMF](2) was obtained and reveals a similar eight-coordinate geometry to [Gd-TREN-Me-3,2-HOPO.2H(2)O] ([3.2H(2)O]). A shape analysis of the coordination polyhedron of 1 reveals that this geometry is best described as a bicapped trigonal prism, poised to accommodate an additional donor atom to give a tricapped trigonal prismatic intermediate. This geometry supports the model that formation of a tris-aquo intermediate for 1 enables fast and associative water exchange.
authors.affiliation: University of California, Berkeley, CA 94720-1460, USA.
authors.forename: Jide
authors.initials: J
authors.lastname: Xu
authors.forename: David G
authors.initials: DG
authors.lastname: Churchill
authors.forename: Mauro
authors.initials: M
authors.lastname: Botta
authors.forename: Kenneth N
authors.initials: KN
authors.lastname: Raymond
mesh_terms: D002614:Chelating Agents / Q000138:chemical synthesis / Q000737:chemistry; D003287:Contrast Media / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005682:Gadolinium / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011522:Protons; D011728:Pyridones / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D003287:Contrast Media; D009942:Organometallic Compounds; D011522:Protons; D011728:Pyridones; C500102:gadolinium(III) 1,2-hydroxypyridonate; D005682:Gadolinium