Direct NMR and luminescence observation of water exchange at cationic ytterbium and europium centres

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

“…120 ms for the M-isomer 1 ). This was quickly followed by similar reports for other tetraamide derivatives, including the corresponding N-methylated compound 11 [24] (or the dimethyl variant thereof [24]) or the sterically more-crowded N-(2-phenylpropyl) analogue 13 [25]. The t M values of the M-isomers for this series of complexes seem to vary with increasing steric bulk of the amide pendent arms, increasing from 120 to 156 to 278 ms (in MeCN at 298 K) for [Eu III (10) [24], and [Eu III (13)] 3 [25], respectively (Table).…”

“…This was quickly followed by similar reports for other tetraamide derivatives, including the corresponding N-methylated compound 11 [24] (or the dimethyl variant thereof [24]) or the sterically more-crowded N-(2-phenylpropyl) analogue 13 [25]. The t M values of the M-isomers for this series of complexes seem to vary with increasing steric bulk of the amide pendent arms, increasing from 120 to 156 to 278 ms (in MeCN at 298 K) for [Eu III (10) [24], and [Eu III (13)] 3 [25], respectively (Table). However, factors other than steric bulk may also influence water exchange, as evidenced by the observation that a Eu 3 -bound water resonance has been detected in the high-resolution 1 H-NMR spectrum of [Eu III (15)] 3 in pure water at ambient temperature [27].…”

Structure, Dynamics, and Computational Studies of Lanthanide‐Based Contrast Agents

“…These complexes show potential as artificial nucleases, NMR shift reagents for anions in aqueous solution and various chiral Eu 3+ and Tb 3+ complexes are of interest as emissive chiral probes in biological media [393][394][395][396][397][398][399][400][401]. Furthermore, the N-substituted tetraamide derivatives (Chart 5.11) have proven useful in understanding the relationship between the solution structure of the Ln 3+ complex and the water exchange rate, a critical issue in attaining optimal relaxation efficiency of CAs for MRI based on the T 1 or the chemical exchange saturation transfer (CEST) mechanisms [175,[402][403][404][405][406][407][408].…”

“…Luminescence and relaxivity studies of the Eu 3+ and Gd 3+ complexes, respectively, confirm the q = 0 value. Ln 3+ complexes of several chiral tetraamide ligands have been reported (Chart 5.11) [397,398,400,401,[432][433][434][435]. Introducing a chiral center with R-or S-configuration at a position α to the amide N (δ to the ring N) imparts ample conformational rigidity to hinder pendant arm rotation and produces the possibility of a maximum of four disatereoisomeric pairs of enantiomers.…”

Yb(fod)3 in the spectroscopic determination of the configuration of chiral diols: A survey of the lanthanide diketonate method

“…6) and locating them symmetrically along the C 3 axis of Yb(fod) 3 ; bonding distances of 2.5 A Ê between the lanthanide and the oxygens were derived from data available on a large set of ytterbium compounds. 20 Averaged geometric parameters were calculated for the CH and methyl protons in the two reference models and are displayed in Table 3 as well.…”