Novel Exciplexes

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With this award, the Chemical Structure, Dynamics, and Mechanism B program supports the research of Professor Joseph P. Dinnocenzo at the University of Rochester. Professor Dinnocenzo and his students investigate novel exciplexes (excited state complexes), especially cationic (positively charged) exciplexes. The research activities provide foundational knowledge about electron transfer and new types of exciplexes. Substances which form exciplexes have potential applications as sensors, as biological probes, and in organic light emitting diodes (OLED). Due to their solubility in water, cationic exciplexes have enhanced potential for development of biological imaging applications. The research provides a rich educational experience for undergraduate, graduate, and postdoctoral students, in synthesis, electrochemistry and time-resolved spectroscopy. This research specifically engages undergraduates from the University of Guam (a minority institution in the US Territory) for summer research opportunities. This group is underrepresented in science, technology, engineering and mathematics (STEM).This project investigates two types of novel, charge transfer exciplex intermediates that were recently discovered in the Dinnocenzo laboratory. One type of exciplex is formed by reaction of cationic, excited state acceptors with neutral donors. Research objectives include determining the electronic nature of the exciplexes (e.g. electronic coupling matrix elements) through theoretical fitting of radiative lifetimes, which are determined by Time Correlated Single Photon Counting (TCSPC) and fluorescence spectra. This project expands the generality of cationic exciplexes by measuring some of their photophysical properties, examining cationic exciplexes in a variety of media (including water), and synthesizing intramolecular examples. A related project investigates examples uncovered in the Professor Dinnocenzo's lab where two exciplex emissions are observed from a single acceptor and donor. Preliminary results are consistent with dramatically different solvent reorganization energies for the two types of exciplexes, indicating major differences in their structures. In this research, students learn how to synthesize, purify, and spectroscopically characterize compounds. Students also receive training in a range of less traditional techniques including transient absorption spectroscopy (TCSPC), fluorometry, electrochemistry, and modern computational chemistry. The students trained through the research are prepared to tackle a variety of multidisciplinary problems in their professional careers.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.