A Bioinspired Cu-Responsive Magnetic Resonance Imaging Contrast Agent with Unprecedented Turn-On Response and Selectivity.

Imaging extracellular Cu in vivo is of paramount interest due to its biological importance in both physiological and pathological states. Magnetic resonance imaging (MRI) is a powerful technique to do so. However, the development of efficient MRI contrast agents selective for Cu, particularly versus the more abundant Zn ions, is highly challenging.

Evaluation of structurally related acyclic ligands OBETA, EHDTA, and EGTA for stable Mn complex formation.

In recent years, significant research efforts have been dedicated to finding efficient and safe alternatives to the currently used gadolinium (Gd)-based MRI contrast agents. Among the most explored alternatives are paramagnetic chelates of the Earth-abundant Mn, which form a prominent class of metal complexes. The design of Mn complexes with enhanced relaxation properties and improved safety profiles hinges on a delicate balance between thermodynamic and kinetic stability, as well as the presence of coordinated water molecules.

Tuning the Properties of Rigidified Acyclic DEDPA Derivatives for Application in PET Using Copper-64.

We present a detailed investigation of the coordination chemistry toward [Cu/Cu]copper of a series of HDEDPA derivatives (HDEDPA = 6,6'-((ethane-1,2-diylbis(azanediyl))bis(methylene))dipicolinic acid) containing cyclohexyl (HCHXDEDPA), cyclopentyl (HCpDEDPA) or cyclobutyl (HCBuDEDPA) spacers. Furthermore, we also developed a strategy that allowed the synthesis of a HCBuDEDPA analogue containing an additional NHBoc group at the cyclobutyl ring, which can be used for conjugation to targeting units. The X-ray structures of the Cu(II) complexes evidence distorted octahedral coordination around the metal ion in all cases.

Improving the In Vivo Stability of [Mn]Mn(II) Complexes with 18-Membered Macrocyclic Chelators for PET Imaging.

We report the [Mn/Mn]Mn(II) complexes of the macrocyclic chelators PYAN [3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane] and CHXPYAN [(4,4,10,10)-3,5,9,11-tetraaza-1,7(2,6)-dipyridina-4,10(1,2)-dicyclohexanacyclododecaphane]. The X-ray crystal structures of Mn-PYAN and Mn-CHXPYAN evidence distorted octahedral geometries through coordination of the nitrogen atoms of the macrocycles. Cyclic voltammetry studies evidence reversible processes due to the Mn(II)/Mn(III) pair, indicating that the complexes are resistant to oxidation.

Relevance of Oxocyclam from Palladium(II) Coordination to Radiopharmaceutical Development.

We provide a comprehensive study of the coordination of with palladium(II), including presentation of a novel bifunctional analogue, bearing an aniline pendant. The complexation of palladium(II) with was examined by various techniques, including NMR analysis and potentiometric titrations which revealed that the Pd(II) complex can adopt different configurations such as -I and -III. In addition, forms a thermodynamically stable palladium(II) complex, the stabilization being attributed to the deprotonation of the amide function.