Thermodynamics and NMR studies of DTPA-bis(methoxyethylamide) and its derivatives. Protonation and complexation with Ln(III)

A Bisamide Derivative of [Mn(1,4‐DO2A)] – Solution Thermodynamic, Kinetic, and NMR Relaxometric Studies

“…In general, the presence of an amide group in an open-chain or macrocyclic aminopolycarboxylate ligand decreases the basicity of the amine N atoms. [14,15] The lower protonation constants of 1,4-DO2AM can be explained by the replacement of the carboxylate pendant arms with the amide groups, which form weaker H bonds with the protonated ring nitrogen atoms. The Σlog K i H value of 1,4-DO2AM is significantly lower than those of 1,4-DO2A, 1,7-DO2A, DO3A and DOTA owing to the absence of protonable carboxylate groups.…”

Potential MRI Contrast Agents Based on Micellar Incorporation of Amphiphilic Bis(alkylamide) Derivatives of [(Gd−DTPA)(H2O)]2−

“…[9,10,14,16] In solution, the presence of H 2 O molecule in the inner sphere was detected in the europium() complex by luminescence lifetime measurements [3,20] and for some dysprosium() complexes by 17 O NMR studies. [11] In attempt to achieve higher proton relaxivity, the Gd III complexes of (DTPA-bisamide) alkyl copolymers with alkyl chains containing six, ten, or twelve ϪCH 2 groups have been synthesized.…”

Synthesis, Equilibrium and Kinetic Properties of Gd3+ Complexes of Three DTPA‐Bis(Amide) Derivatives Containing Stable Nitroxide Free Radical Substituents

“…[6] [b] Ref. [7] The first protonation constants of the different DTPAbis(amide) derivative ligands are quite similar. The second protonation constants are somewhat lower for L 1 and L 2 , containing two monosubstituted -C(O)NHR amide groups, than for L 3 , containing two disubstituted -C(O)NR 2 amide groups.…”

“…Similar results were found for L 4 and L 5 , so the amide group does not decrease the logK 2 H value of the DTPA derivative so significantly if both amide hydrogens are replaced with alkyl (or aryl) groups. [7] This result was explained by the assumption of the formation of more hydrogen bonds in the ligands containing amide [-C(O)NHR] hydrogen atoms. [7] The titration curves of the ligands obtained in the presence of equivalent amounts of Zn 2ϩ (Figure 1) could be fitted with lower values of the standard deviations and fitting parameters (the difference between the experimentally ascertained and the calculated volumes of base needed to attain a given pH value) if formation of the species ZnL, ZnHL and ZnH 2 L was assumed.…”

“…[7] This result was explained by the assumption of the formation of more hydrogen bonds in the ligands containing amide [-C(O)NHR] hydrogen atoms. [7] The titration curves of the ligands obtained in the presence of equivalent amounts of Zn 2ϩ (Figure 1) could be fitted with lower values of the standard deviations and fitting parameters (the difference between the experimentally ascertained and the calculated volumes of base needed to attain a given pH value) if formation of the species ZnL, ZnHL and ZnH 2 L was assumed. The stability constants are defined as described in Equation (2), where i ϭ 0, 1 or 2.…”