Characterization of Azaphenalenes with Inverted Singlet-triplet Gap for Photocatalytic Applications

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

With funding from the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Etienne Garand of the Department of Chemistry at the University of Wisconsin-Madison is studying the electronic structure of azaphenalenes, a class of molecules with very unusual and interesting optical properties. The goal of this research is to understand the origin of these unusual characteristics and how they evolve as a function of molecular structure. This understanding will be used to create models to guide development and refinement of these chromophores for use in organic light emitting devices and as metal-free photocatalytic materials for the conversion of solar energy into stored chemical energy. The project includes components of organic synthesis, laser spectroscopy and computational chemistry, and is therefore well suited for the development of a highly skilled scientific workforce. Participants in this project will also contribute to departmental programs aimed at broadening diversity and representation at the graduate education level. Under this award, the research team of Professor Etienne Garand at the University of Wisconsin-Madison will study the electronic structure of azaphenalenes, a class of molecules that is predicted to have an inverted singlet-triplet gap. This unusual molecular characteristic, which stands in formal contradiction to Hund’s rule, can lead to interesting optical properties for the development of organic light-emitting devices and photocatalytic graphitic carbon nitride materials. Specifically, this project aims to (i) directly quantify the singlet-triplet gap in these species via cryogenic anion photoelectron spectroscopy and use these results to benchmark the accuracy of various computational electronic structure approaches; (ii) vary the chromophore core substituents in order to develop a semi-empirical model that enables rapid estimation of the magnitude of the inverted singlet-triplet gap and (iii) measure the excitation energy of the reactive charge transfer state relative to the singlet reservoir state of such a system to optimize its potential for photocatalytic activity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.