Synthesis and Characterization of Pyridine and Pyrazine-Derived Tripodal Ligands for Use in Novel Mn(II)-Based MRI Contrast Agents

Anna Friedman
Anna Friedman

Anna Friedman is a rising senior (’22) from San Carlos, California. She graduated from Castilleja School in 2018. Currently, Anna is double majoring in Chemistry and Italian at Wesleyan University. She enjoys volunteering as a clinic escort, drinking coffee, working with kids, and playing volleyball. After she graduates, Anna plans to live her best life in Italy for a time and then attend medical school.

Abstract: Molecular resonance imaging (MRI) is a powerful technique used for visualizing structures inside the body. In approximately 40% of MRI scans, a contrast agent is utilized to improve the definition of soft tissues in the scan. After injection into the bloodstream, contrast agents can increase the visibility of blood vessels, tumors, and areas of inflammation. The most common MRI contrast agents are gadolinium chelates, meaning that the ligands in the complex are coordinated to a central gadolinium(III) ion. Unfortunately, in patients with renal insufficiencies, repeated use of gadolinium-based contrast agents has been demonstrated to result in severe ailments like gadolinium toxicity and nephrogenic systemic fibrosis. Thus, it is important to research alternative contrast agents that are less harmful and still effective. Previous studies have shown that small, water-soluble, polydentate ligands are preferable for creating metal-ligand complexes. The ligands explored here are specifically composed of nitrogen-containing heterocycles because the nitrogen atoms can effectively coordinate to metal ions. Manganese is being examined as a potential central metal ion because it is present in the human body, forms paramagnetic complexes, and is not highly susceptible to oxidation. The present research explores the syntheses and characterizations of different tripodal ligands, including tris(2-pyridylmethyl)amine (TPAA), 6,6′-[((pyridin-2-ylmethyl)azanediyl) bis(methylene)] dipicolinic acid (H2TPADA), and 6-​[[bis(2-​pyridinylmethyl)​amino]​methyl]​-​2-​pyrazinecarboxylic acid (brenda). Here, these pyridine and pyrazine ligands are compared and evaluated for potential use in transition metal-based MRI contrast agents.

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