Professor Peter Dinolfo of Rensselaer Polytechnic Institute

"Utilizing Stark Spectroscopy to Characterization of the Excited State Properties of Chromophores and Photoredox Catalysts"

Stark spectroscopy measures the change in spectra properties of molecules in the presence of large electric fields. This technique has been particularly useful in characterizing the change in dipole moment and polarizability of electronic transitions. This information is important when designing molecular chromophores for use in solar energy conversion, artificial photosynthesis, photocatalysis, among others. Herein, the Stark results for several classes of molecular chromophores is described, including perylene diimides and several photoredox catalysts. We have recently characterized the photophysical properties of three distinct isomers of dodecylthio-functionalized perylene diimides. Significant differences in the electronic absorption and emission spectra, and excited state lifetimes were observed between the 1,6-, 1,7- and 1,6,7-ThioPDI. Stark electroabsorption and electrofluorescence spectroscopy provide detailed information on how the substitution pattern affects the excited state properties. Additionally, we have begun to explore the Stark response of two series of organic based photoredox catalysts, including 9-mesityl-acridiniums and carbazolyl dicyanobenzenes. The magnitude of charge transfer determined via Stark spectroscopy can be used to design new, more efficient organic based photoredox catalysts.