NMR, Relaxometric, and Structural Studies of the Hydration and Exchange Dynamics of Cationic Lanthanide Complexes of Macrocyclic Tetraamide Ligands

摘要: The solution structure and dynamics of metal-bound water exchange have been investigated in a series lanthanide complexes primary, secondary, tertiary tetraamide derivatives 1,4,7,10-tetraazacyclododecane. In the gadolinium at ambient pH, lifetimes (τm) determined by 17O NMR were sufficiently long (19 μs for [Gd·2]3+, 298 K, 17 [Gd·3]3+, 8 [Gd·4]3+) to limit measured relaxivity. Direct 1H observation bound resonance is possible corresponding Eu low temperature CD3CN, rate proton about 50 times faster twisted square antiprismatic isomer (m) than isomeric (M) complex. ratio these two isomers sensitive steric demand amide substituent, with m/M = 2 [Eu·4]3+, but 0.25 [Eu·2]3+. slowness coordinated has allowed prototropic be studied:  basic media deprotonat...