Collaborative Research: Theory and Synthesis of Strained Cyclic Photoswitches Towards Controlling Isomerization and Cycloadditions

With the support of the Chemical Mechanism, Function, and Properties Program of the Division of Chemistry, Professor Michael Kienzler of the Department of Chemistry at the University of Connecticut and Professor Steven Lopez of the Department of Chemistry at Northeastern University are collaborating across synthetic and theoretical chemistry to study the reactivity of molecular photoswitches. Molecular photoswitches use light to trigger controllable changes in molecular function. In this project, the PIs are using ring strain as a second means of controlling and enhancing the photoswitching functions. Using ring-strain to increase molecule reactivity is well-established in chemistry. This proposal combines these two ideas to develop cyclized photoswitches to generate ring-strain reversibly and study the activation of functional groups in the rings for wavelength-dependent spatiotemporal control of target reactions. Results from this research project will significantly impact organic chemistry, energy storage, biophysics, and chemical biology. Furthermore, this interdisciplinary project includes a substantial educational framework for supporting STEM students from high school through graduate level chemistry. The long-term goal of this collaboration is to understand the photophysical effects of ring-strain on photoswitches and to demonstrate that the reversible generation of ring-strain can accelerate otherwise unfavorable photochemical reactions. Molecular photoswitches reversibly interconvert between isomers when irradiated with different wavelengths of light and have been a subject of fascination in the chemical community for over a century. Photoswitches like azobenzenes, fulgides, diarylethenes, and hydrazones have numerous applications in widely disparate scientific fields, from nonlinear optics to pharmacology. The broader scientific impacts include light-patterned polymerization to install photoswitches directly into the polymer backbone and to use different wavelengths of light to tune the reactivity of strain-promoted cycloadditions for bioorthogonal labeling. High throughput computations will create datasets of ground- and excited-state properties to guide experimental efforts. This collaborative work will produce structure-reactivity relationships needed to inform the discovery of new photoswitches and their reactions. 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.