Date of Award
Doctor of Philosophy
Arthur H Winter
The work contained in this dissertation sheds a light on a previously under-investigatedclass of stable radicals; aryl dicyanomethyl radicals. Organic compounds with spin unpairedelectrons, dubbed free radicals, are often reactive and tend to decompose quickly under normalatmospheric conditions. If organic radicals are stabilized, they are attractive candidates for stimuliresponsive materials. If these stabilized radicals are to be useful in future materials applications,studies must be performed to learn as much as possible. This work will describe the journey fromstart to dissertation on the synthesis and analysis of new various dicyanomethyl radicals for theirstimuli responsive properties. Aryl dicyanomethyl radicals exist in an equilibrium between a closed shell diamagneticdimer and two open shell paramagnetic radicals. The equilibrium of each differentdicyanomethylene radical is dependent upon both the substituents on the aryl ring as well as thesolvent these radicals are studied in. Another factor that determines the equilibrium of thesecompounds is temperature. Thermal stimulation, in both solution and the solid-state, leads tohomolysis of the radical-radical sigma bond into two identical radicals for intermolecular dimers.Each compound is investigated by variable temperature electron paramagnetic resonancespectroscopy (VT-EPR) in order to determine thermodynamic values. With thermodynamic data,binding constants for each compound can be calculated from a generated van't Hoff plot. Inaddition to VT-EPR analysis, some of these radicals have vibrant absorbances in the visible region,so variable temperature UV-Vis spectroscopy can also be performed on select radicals. Variousother methods of dimerization other than normal "sigma-dimerization" have been studied as well.This class of organic radicals proves to be rich in potential for stimuli responsive materials.
Peterson, Joshua, "Combining synthesis, computation, and spectroscopy to investigate dicyanomethyl radical dimerization" (2020). Graduate Theses and Dissertations. 17857.