EAGER: Controlling Photochemistry via Spatially Selective Excitation

Northern Illinois University, Dekalb IL

Investigators

Abstract

In this project funded by the Chemical Structure, Dynamics, and Mechanisms-B (CSDM-B) Program of the Chemistry Division, Professor Evgueni Nesterov of Northern Illinois University investigates a new general principle to control photochemical reactions through the use of liquid crystalline media and plane polarized light. Liquid crystals (LCs) have properties between those of conventional liquids (in that they can flow) and those of solid crystals (in that they are oriented in a very specific way). Liquid crystal displays are widely used - one example is in digital watch faces. This research seeks to use liquid crystals in capturing light and specifically and uniformly redirecting the light's energy into specific chemical reactions. The project is high risk as such a concept has not yet been demonstrated in practice. If successful, this research may establish a new paradigm for controlling photochemical reactions so that very specific chemical products are made. This can potentially lead to new environmentally benign chemical processes which rely on light as a source of energy for chemical transformations. Students participating in this program benefit from multidisciplinary and collaborative training, which allows them to become highly competitive in the technical job market. They also contribute to society through participation in special hands-on activities targeting local K-12 education. The ultimate goal of this early-stage exploratory program is to develop and experimentally confirm a novel paradigm for controlling the course and selectivity of photochemical reactions through the uniform molecular alignment of photoreactive compounds in liquid crystalline (LC) media and spatially selective excitation of specific electronic transitions with plane-polarized light. In contrast to the conventional ways of controlling photochemical selectivity by imposing geometrical restrictions on the photoreactive molecule, this approach relies on selective excitation of the particular electronic transitions leading to a desired photochemical transformation. The research seeks to design and synthesize a series of photochemically reactive compounds with enhanced ability to align in nematic LC media, which can display excitation-selective photochemical reactivity. The research group provides detailed experimental analysis and characterization of their LC-imposed alignment and transition dipole moment orientation using UV/vis polarization spectroscopy. This research program may establish a new paradigm for controlling and enhancing selectivity of photochemical reactions. This can potentially lead to new environmentally benign chemical processes which rely on light as a source of energy for chemical transformations. In addition to these practical benefits, the broader impacts of this work include benefits to the society from multidisciplinary training of students in STEM disciplines, both through student involvement in advanced research and participation in special outreach activities developed with the goal of improving public awareness and appreciation of modern science and technology, particularly among younger generations. 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.