An NMR relaxivity and ESR study of the interaction of the paramagnetic manganese(II) and gadolinium(III) ions with anionic, cationic and neutral water-soluble polymers and their mixtures

Design of High-Relaxivity Polyelectrolyte Nanocapsules Based on Citrate Complexes of Gadolinium(III) of Unusual Composition

“…However, the limiting value of the relaxivity curve for PEI solution is much higher than that of aqueous solution of Gd(III) at the same pH (4 vs. 0.4 mM −1 s −1 ). A similar effect was previously discovered by the authors of this paper not only for Gd(III), but also for Mn(II) [26]. The aforementioned phenomenon could not be caused by the binding of the hydrolyzed form of metal due to the competition of OH --ions and amino groups of the branched PEI molecule for binding with metal ions [46], even though gadolinium ions do not form complexes in solutions with ammonia, ethylene diamine, and other low-molecular amines.…”

“…NMR relaxation measurement is highly informative tool not only for the investigation of paramagnetic cation complexes (including development of new types of CAs for MRI), but also for the study of nanosized objects in solutions. Features of the mechanism of proton relaxation in gadolinium solutions (an increase in the relaxivity due to the slow-down of rotation of Gd(III) ions bound to nanoparticle) revealed not only aggregation in the solutions of surfactants [22,23] or lipophilic macrocycles [24,25], but also the binding of cations with polymers [26], or graphene oxide [27,28]. In addition, the authors of this current paper have previously discovered that metal ion complexes can form associates with oppositely charged ions of surfactants, macrocycles, or polymers [29][30][31][32].…”

NMR-Relaxometric Investigation of Mn(II)-Doped Polyoxometalates in Aqueous Solutions

“…The region of elevated R1 relaxivity values, which was explained above by the slow rotation of the cluster, disappeared, and, based on the high R2/R1 ratio values (4.75-4.95), almost up to pH 7 manganese ions are present as aqua ions. In general, the profile of curves 2 in Figures 8 and S6 is similar to that of curves 3 depicted in our previous study of the state of manganese(II) in polymer solutions [22]. The decrease in relaxivity above pH 7 and the decrease in the hydration of manganese ions are explained by the binding of these ions to numerous amino groups in the branched polymer, which loses its cationic nature upon deprotonation of its ammonium groups.…”

“…This ratio is 4.8 ± 0.2 for [Mn(H 2 O) 6 ] 2+ ( q = 6), and it decreases to 1.2 ± 0.2 for the complex with diethylenetriaminepentaacetic acid, where all water molecules of the first coordination sphere are substituted with the donor atoms of the chelating ligand ( q = 0). Thus, the relaxation rate ratio R 2 / R 1 is an important tool for assessing the degree of substitution of water molecules in the first coordination sphere of manganese(II) ions with donor atoms both during complex formation and association processes [ 21 , 22 , 23 , 24 ].…”

Easy colorimetric detection of gadolinium ions based on gold nanoparticles: key role of phosphine-sulfonate ligands

“…44,45 The interaction between Gd 3+ ions and an increased number of styrene sulfonate groups accounted for the strong polystyrenesulfone-Gd 3+ binding. 47 Here, hydrogen bonds are formed with the ligands from the rst coordination sphere of Gd 3+ ions. These interactions can thus be easily broken by changing the chemical environment as demonstrated by QCM-D experiments during the rinsing step (vide supra).…”