Unprecedented Kinetic Inertness for a Mn2+‐Bispidine Chelate: A Novel Structural Entry for Mn2+‐Based Imaging Agents

摘要: The search for more biocompatible alternatives to Gd3+ -based MRI agents, and the interest in 52 Mn PET imaging call ligands that form inert Mn2+ chelates. Given labile nature of , high inertness is challenging achieve. strongly preorganized structure 2,4-pyridyl-disubstituted bispidol ligand L1 endows its complex with exceptional kinetic inertness. Indeed, MnL1 did not show any dissociation 140 days presence 50 equiv. Zn2+ (37 °C, pH 6), while recently reported potential agents MnPyC3A MnPC2A-EA have half-lives 0.285 h 54.4 h under similar conditions. In addition, relaxivity (4.28 mm-1  s-1 at 25 °C, 20 MHz) remarkable a monohydrated, small chelate. In vivo experiments mice determination tissue content evidence rapid renal clearance . Additionally, could be radiolabeled revealed good stability biological media.