Gd3+ chelates of interest in magnetic resonance imaging (MRI): studies using 17O NMR and EPR at several magnetic fields

Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications

“…In 1993 Micskei et al showed that the water exchange rates for [Gd(DTPA)(H 2 O)] 2- and [Gd(DOTA)(H 2 O)] - (Chart ) were lower by about 3 orders of magnitude compared with the Gd 3+ aqua ion. The Merbach group has since shown that Gd(III) water exchange rates can vary over 4 orders of magnitude. ,,,− Recently a tripositive europium complex was shown to have an exceedingly slow water exchange rate in a water−acetonitrile mixture . If the analogous Gd(III) complex has a similar rate (which is likely), then the rate of water exchange would vary by almost 7 orders of magnitude for known complexes!…”

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

“…However, more-recent studies, catalyzed by the pioneering work of Andre Merbach and his group, have revealed that this is not, in fact, the case. For example, the water residence lifetimes (t M ) of two common clinical agents, [ [5], some two orders of magnitude higher than that of the aqua Gd 3 ion [6 ± 11]. Merbach and coworkers [12] also discovered that t M of bound water in the neutral diamide complex [Gd III (DTPA)(BMA)] 0 , was even higher, ca.…”

Gadolinium Complexes as Contrast Agent for Cellular NMR Spectroscopy

“…At 298 K, T 1e calculated from parameters reported [45,64,65] is approximately 1.35 × 10 −7 and 2.01 × 10 −6 s for aqua Gd 3+ and Gd-DOTA complexes respectively. The time constant for the rotational diffusion is much shorter than that for the exchange between the inner sphere and the outer sphere of gadolinium complexes as (τ r , τ m ) = (2.9 × 10 −11 s, 1.2 × 10 −9 s) and (9.0 × 10 −11 s, 2.0 × 10 −7 s) at 298 K for aqua Gd 3+ and Gd-DOTA complexes, respectively [65,66]. Because τ r << τ m << T 1e , Equation (2) is expressed as 1/τ c ≈ 1/τ r by neglecting τ m and T 1e .…”