Mn(II) based T₁ and T₂ potential MRI contrast agent appended with tryptamine: Recognition moiety for Aβ-plaques

We report the synthesis and characterization of manganese(II) complexes having pentadentate ligands L₁ (2,6-bis(1-(2-phenyl-2-(pyridin-2-yl)hydrazono)ethyl)pyridine), L₂ (methyl 2,6-bis((E)-1-(2-phenyl-2-(pyridin-2yl)hydrazono)ethyl)isonicotinate), L₃ (N-(2-(1H-indol-3-yl)ethyl)-2,6-bis((E)-1-(2-phenyl-2-(pyridin2yl)hydrazono)ethyl)isonicotiamide) and their application as dual contrast agents for simultaneous T₁ and T₂ weighted magnetic resonance imaging. Single crystal analysis of all the complexes [Mn^IIL₁, Mn^IIL₂ and Mn^IIL₃] confirm the formation of novel seven-coordinate manganese complexes with an inner sphere water and perchlorate ion. The Magnetic Resonance Imaging (MRI) contrast agent [MnL₂] was further modified by incorporating tryptamine as a binding moiety specific to Amyloid Beta-fibrils (Aβ-fibrils) in Alzhiemer's disease (AD) and it's in vitro evaluation for specific binding with Aβ-fibrils indicated as a bio-marker of AD.