Rigid and Compact Binuclear Bis‐hydrated Gd‐complexes as High Relaxivity MRI Agents

Abstract

The first binuclear Gd‐complex of the 12‐membered pyridine‐based polyaminocarboxylate macrocyclic ligand PCTA was synthesized by C−C connection of the pyridine units through two different synthetic procedures. A dimeric AAZTA‐ligand was also synthesized with the aim to compare the relaxometric results or the two ditopic Gd‐complexes. Thus, the 1H relaxometric study on [Gd2PCTA2(H2O)4] and on [Gd2AAZTA2(H2O)4]2− highlighted the remarkable rigidity and compactness of the two binuclear complexes, which results in molar relaxivities (per Gd), at 1.5 T and 298 K of ca. 12–12.6 mM−1 s−1 with an increase of ca. 80 % at 1.5 T and 298 K (+70 % at 310 K) with respect to the corresponding mononuclear complexes.

Advances in Characterizing Gas Hydrate Formation in Sediments with NMR Transverse Relaxation Time

“…MRI is an effective tool for investigations in physical, chemical, life, and clinical sciences as it noninvasively maps the liquid water protons with high spatial resolution in three dimensions [122][123][124][125]. MRI technique has been vastly used to observe the dynamic process of hydrate formation and decomposition in hydrate-bearing sediments due to its [111]); (b) The original CT image of hydrate-bearing sediments with KI solution (modified from [107]); (c-f) The formation process of gas hydrate monitored by MRI, and (g,h) SEM images from gas hydrate in sediments (modified from [114,121]).…”

“…MRI is an effective tool for investigations in physical, chemical, life, and clinical sciences as it noninvasively maps the liquid water protons with high spatial resolution in three dimensions [122][123][124][125]. MRI technique has been vastly used to observe the dynamic process of hydrate formation and decomposition in hydrate-bearing sediments due to its immediacy of image acquisition (Figure 8c-f).…”

Recent progress in the chemistry of 12-membered pyridine-containing tetraazamacrocycles: from synthesis to catalysis

“…Botta, Tei and coworkers recently reported the synthesis of binuclear Gd( iii ) complexes. 32 In particular, the synthesis of PCTA dimer L27 ligand bearing a 4,4′-bipyridine backbone was reported (Scheme 10). The synthesis relied on the use of 4-bromo-2,6-bis-(bromomethyl)-pyridine ( 41 ) and tosyl-protected triamine 1b to assemble the macrocycle 42 , via the Richman–Atkins reaction.…”

The effect of Gd-DOTA locations within PLGA-b-PEG micelle encapsulated IR-1061 on bimodal over-1000 nm near-infrared fluorescence and magnetic resonance imaging

“…The enhancement of r 1 relaxivities is attributable primarily to the repression of the global rotational motions when the Gd (III) chelates are conjugated to high molecular relaxivity reagents such as polymers in micellar structures. 6,20,31,[34][35][36][37] . This enhancement is related to the number of acetate groups of DOTA substituted by polymer chains enhancing the structure stability and kinetically inert manner compared to that of Gd chelates resulting in the elongated rotation time  r .…”

“…In this work, the relaxometry was performed at 3T, and the relaxivity of PLP-D[70] was 16 mM −1 s −1 and PL-D-P [70] was 26 mM −1 s −1 . [31][32][33] The relaxivities of the micelle structures display higher values than those of small molecules such as Gadovist® (3.8 mM −1 s −1 ). The enhancement of r 1 relaxivities is attributable primarily to the repression of the global rotational motions when the Gd(III) chelates are conjugated to high molecular relaxivity reagents such as polymers in micellar structures.…”