The Excited State Behavior of Ru(II) Photodrugs

With this award, the Chemical Structure, Dynamics, and Mechanism-B program is supporting the research of Professor Sherri McFarland at the University of Texas, Arlington to examine the excited state photophysics and redox properties of Ru-based photosensitizers. Photosensitizers are compounds that can trap the energy of light and use it to effect a useful chemical reaction.

Examples of this include solar energy conversion, catalysis, and photodrugs. This project focuses on a particular class of such photosensitizers that show promise in cancer therapy, but have many unanswered questions about their mode of action. The work will investigate the fundamental photophysical and electrochemical properties of oligothiophene-containing ruthenium compounds specifically, and reveal the details of photocatalytic mechanisms in which they can participate.

It will also explore how the behavior of these photosensitizers can change as a function of its environment, e.g., agglomeration effects and the influence of simulated biological structures. The proposed work will train graduate and undergraduate students in highly multidisciplinary research at the interface of chemistry, biology, physics, and engineering.

The knowledge and skills these trainees will acquire will give them tools necessary for success as future research scientists in cutting-edge multidisciplinary fields ranging from photomedicine to solar energy conversion and chemical biology. The broader impact objectives will simultaneously equip tomorrow’s leaders with skills in science communication and expose them to entrepreneurship and commercialization as it relates to bringing scientific discoveries from the laboratory to society.

It will also provide curriculum-based research opportunities for undergraduate students that would otherwise not have the opportunity to experience scientific research in a real-world laboratory setting, expanding diversity in our next generation of emerging scientists.

This project project will examine the excited state photophysics and redox properties of oligothiophene-containing Ru(II) complexes, compounds that have important applications as photosensitizers in fields ranging from solar energy conversion to photodrugs. The project also aims to develop the photophysical model(s) for these photosensitizers in complex biological environments.

We will synthesize and characterize oligothiophene-appended Ru(II) photosensitizers, [Ru(LL)2(IP-nT)]2+ that differ in the number of thiophene rings (nT), the types of substituents on the thiophene rings, and the co-ligands (LL). The modifications are designed to systematically vary redox potentials and triplet state characteristics, and to alter the covalent and noncovalent associations typical of oligothiophenes.

Electrochemical and photophysical techniques will be used to test hypothetical photoredox catalysis mechanisms in complex substrates, where synthetic and cell-derived vesicles will be used to model how photosensitizer response modulates in confined matrices, e.g., a lipid bilayer. The results will advance the field of Ru(II)-oligothiophene photosensitization.

With a mechanistic understanding of oligothiophene-containing Ru(II) photosensitizers, there exists the opportunity to create better next-generation photosensitizers for photocatalytic applications. The broader impact activities are equally focused on exposing STEM scientists to science communication and entrepreneurship based on past translational research and commercialization efforts related to light-molecule interactions.

The training program will cover outreach, education, and curriculum, emphasizing the process from fundamental discovery to societal application, and provide opportunities for researchers to improve their science communication skills. Curriculum-based research opportunities for undergraduate STEM students will be designed and delivered to ensure that a larger percentage of these students receive hands-on research experience during their degree programs.

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.