Photoresponsive Vinyl Azide Crystals

University Of Cincinnati Main Campus, Cincinnati OH

Investigators

Abstract

In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Anna D. Gudmundsdottir of the Department of Chemistry at the University of Cincinnati is studying the fundamental science behind "photodynamic" crystals. These are unusual substances which move as they are exposed to light. When illuminated, photodynamic crystals can twist, bend, leap, crawl or shatter. This behavior holds the potential for development of new devices in which light is converted into motion, such as actuators and sensors. The interdisciplinary nature of this project, which connects photochemistry and materials science, provides diverse educational training opportunities for students. Through this research, students are prepared as future scientists who can address the technical challenges facing society. Both high school and college undergraduate students will be recruited from groups underrepresented in science to carry out research in the Gudmundsdottir laboratory. Students will also be provided with educational activities that focus on their professional development. The Gudmundsdottir research group investigates photodynamic behavior of crystalline vinyl azide derivatives which, upon light exposure, dissociate to triplet vinylnitrenes and molecular N2. The mode of nitrogen release within the crystal lattice is distinctive for each vinyl azide derivative. Some crystals tolerate a build-up of large N2 bubbles within the lattice before cracking, whereas others release N2 immediately with light exposure. In this research, structural factors which control the release of N2 molecules within the crystal are identified. As part of this research, solid-state photoreactivity of these compounds is investigated by performing laser flash photolysis of nanocrystals. These studies are designed to characterize the transients formed within the crystals and determine the solid-state kinetics of these transients. X-ray crystallography and photoproduct identification are critical elements of this study. Solid-state reaction mechanisms are supported by quantum chemical calculations. Collectively, these data make it possible to elucidate detailed solid-state reaction mechanisms and explain how the crystal lattice controls both the reactivity and the photodynamic behavior of vinyl azide derivatives. 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.