Towards the Synthesis and Characterization of Mn(II) Polypyridyl Complexes for Photochemical Applications

Abstract

Coordination complexes of transition metals that have long-lived charge-separated excited states have many photochemical applications such as solar energy conversion and photoredox catalysis. The traditionally used transition metals are in the second- and third-row, including Ir(III), Ru(II), and Re(I), which are both expensive and scarce. For this reason, researchers have attempted to find are developing photoactive complexes with alternative other transition metals. For this project, manganese was chosen as the metal-of-focus as it is cheap, relatively non-toxic, and has a wide range of oxidation states. Our goal is to prepare photoactive manganese complexes: In particular, Mn(II) is air-stable, making it a convenient starting point for research. In this work, we describe the synthesis of tridentate polypyridyl ligands N,N’-dimethyl-N,N’-dipyridin-2-ylpyridine-2,6-diamine (ddpd) and di-2,6-(2-pyridylcarbonyl)pyridine (dcpp). The synthesis of their corresponding Mn(II) complexes was then attempted but resulted in the protonation of the ligands without any coordination occurring.