RUI: Photophysics of Small-Molecule and Polymeric Fullerene-Transition Metal Organometallic Supramolecular Systems

Northern Kentucky University Research Foundation (Do Not Use), Highland Height KY

Investigators

Abstract

RUI: Photophysics of Small-Molecule and Polymer Fullerene-Transition Metal Organometallic Supramolecular Systems The Macromolecular, Supramolecular, and Nanochemistry Program supports Professor Keith A. Walters of Northern Kentucky University for the synthesis and spectroscopic behavior of organometallic systems that combine fullerenes and transition metals. Relatively simple Diels-Alder reactions have allowed for the functionalization of these molecules and provided an opportunity to incorporate fullerene into pi-conjugated ligand structures and ultimately to form complexes with various transition metals (e.g., Rhenium and Ruthenium). Spectroscopic analysis of the ensuing systems indicates the presence of multiple excited states and decay pathways. Stark absorption spectroscopy is being used to confirm that charge transfer is taking place. In this work, the researchers will continue these investigations with several goals: 1) to investigate other reaction methodologies to improve the yields of the reactions, including the use of microwave-assisted reactions; 2) to explore other polyaromatic moieties (e.g., coronene and corannulene) in analogous systems to better understand the role of the organic subunit in the observed photophysics; 3) to modify the linkages between the transition metal and fullerene to possibly increase their excited state interaction; and 4) to expand efforts beyond small molecules and prepare poly(phenylene-ethynylene)-type polymers containing the substituted fullerene building blocks and transition metal chromophores. The research will expand knowledge in the field of organometallic supramolecular chemistry and provide new structures for use in various molecular device applications, for example in solar energy conversion. Over the past two decades, there has been keen interest in the design of molecular devices for use in energy conversion (e.g., solar cells) and charge transport (e.g., molecular wires). This approach has evolved from purely organic polymeric systems, which require considerable redesign to modify the system?s properties, to organometallic systems that utilize transition metal chromophores to tune the organic polymer. The Walters research group has been interested in these systems for some time, where both the synthetic challenges and system characteristics upon light excitation are explored. This work is centered upon methods developed by undergraduate researchers that attach a simple chemical handles to fullerene. Organometallic systems bringing together these modified fullerenes and transition metals have exhibited complex behavior following light excitation that suggests charge does move between portions of the molecule, a necessary component in the desired molecular devices. Moving forward, this research seeks to further understand how these molecules interact with light. The acquired knowledge will also be applied in the creation of polymeric systems, an essential evolutionary step in the use of these materials in the desired new molecular devices. In addition, undergraduate researchers will work with other department instructors and with the chemistry student group at Northern Kentucky University in their outreach activities to advance the importance of alternative energy and nanoscale materials through presentations and other demonstrations.