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Abstract

Heteronuclear lanthanide complexes have gained an increased level of interest recently, due to their high potential for application in various molecular imaging techniques. They appear primarily as the most rational choice for agents to be used in multimodal imaging approaches.[1-2] Namely, due to their versatile physicochemical properties, they are widely used in MRI or luminescence imaging. Several lanthanide complexes have been reported recently with the potential to be used as multimodal agents. Depending on the approach the final ligand structure contained a single chelator for the lanthanide ion, or consisted of two chelating units, consequently bearing same or different Ln3+. Following these principles, we designed and synthesized a ligand containing two different chelators where the antenna acts not only as a linker between these two chelators, but also as an integral component in one of their structures. The macrocyclic, DOTA-type moiety of this ligand forms a stable complex with Eu3+ and Gd3+ which exhibit the expected luminescence emission and relaxometric characteristics, respectively. An aryl-containing acyclic chelator 5A-PADDTA (abbreviated from 5-aminoisophthalamide diethylenediaminetetraacid) of this ligand also forms complexes with lanthanides and their existence is confirmed by the means of luminescence and NMR spectroscopy. Depending on the choice of the metal ion (Gd3+, Tb3+, Eu3+, Nd3+, Yb3+ or Er3+), the system could act as a potential dual-modal (MRI / Vis or NIR luminescence imaging) or dual-emissive (luminescence imaging at various wavelengths in Vis/NIR region) contrast agent.