An Investigation of Antenna, Ligand Side-chain, and Metal Ion Effects on the Optical and MRI Properties of Bimodal Lanthanide (III) Complexes

Magnetic Resonance Imaging (MRI) is a leading anatomical imaging modality for disease diagnosis. With the aid of Gd3+ based contrast agents, high resolution images of biological structures can be obtained. However, there is an increased need for contrast agents that are responsive to specific analytes and chemical environments. Paramagnetic Chemical Exchange Saturation Transfer (PARACEST) agents that utilize a paramagnetic lanthanide ion chelated with a ligand have shown great promise in this area. Lanthanide ions also possess luminescence properties that do not suffer from common limitations of conventional optical imaging agents such as autofluorescence and photobleaching. The projects described in this thesis aim to capitalize on the dual MRI and optical characteristics of lanthanide ions through the synthesis and characterization of a series of bimodal Eu3+ and Tb3+ complexes. Chapter one contains an overview of lanthanide complexes, MRI, and optical imaging. Chapter two details a study on the effect of quinoline-amide substituent position on the optical properties and stabilities of a library of Eu3+ complexes. In chapter three the effect of varying side-chain identities of Tb3+ and Eu3+ complexes is investigated. The results obtained from these projects indicate that minor changes in ligand structure can have a significant impact on the imaging properties and stabilities of these lanthanide complexes. This insight can be applied towards further optimization of the MRI and optical properties of bimodal Ln(III) complexes