Unexpectedly Large Change of Water Exchange Rate and Mechanism on [Ln(DTPA-BMA)(H2O)] Complexes along the Lanthanide(III) Series

Synthesis, Variable Temperature and Pressure 17O NMR Study of Bis(alkylamide) Derivatives of [(Gd-DTPA)(H2O)]2 − An Assessment of the Substitution Effect on Water Exchange Kinetics

“…[6Ϫ9] The determination of water exchange rates for a set of lanthanide complexes of DTPA-BMA (from Nd 3ϩ to Ho 3ϩ ) has shown that the exchange rate increases when the ionic radius of the lanthanide decreases. [10] These two latter observations show the importance of steric hindrance in the coordination cage on the water exchange rate. Furthermore, the charge has also been invoked as a factor affecting residence times which are particularly long, as for [Gd(DTMA)(H 2 O)] 3ϩ (τ M ϭ 17 µs at 278 K), [11] or short, as for [Gd(PCTP- [13])(H 2 O)] 3Ϫ (τ M ϭ 8 ns at 278 K).…”

Alternatives to Gadolinium-Based Metal Chelates for Magnetic Resonance Imaging

“…The water exchange rates of lanthanide complexes of both DTPA and DOTA amides show a strong dependence on the lanthanide ionic radii 131. The exchange rates in the lanthanide complexes of 15 is nearly constant for the lighter lanthanides (Ln = Nd 3+ , Eu 3+ ), but increases sharply for the heavier ones from Gd 3+ to Ho 3+ (Figure 11a).…”

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

“…The molar ratios of bound vs. bulk water were determined directly from the low-temperature 1 H-NMR integration values. The VT- 17 O-NMR linewidth data were fitted by following procedures published by Merbach and co-workers [12].…”

“…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. 2.2 ms.…”