Organic molecules with high-spin ground states will be prepared and studied as models for building ferromagetic organic materials. Tetramethyleneallene (TMA) is one of the species that will be prepared and the electronic structure will be determined. This tetraradical can be viewed as a union of two planar pi-systems, each a trimethylenemethane triplet biradical, in an orthogonal arrangement. TMA is expected to display an extremely strong quintet spin preference, since it provides powerful exchange coupling of the orthogonal triplet trimethylenemethane subunits. This concept will be tested experimentally. A second class of high-spin ground state compounds will be prepared and studied, which consist of two carbons in a trimethylenemethane biradical fused to an array of aromatic rings. These high-spin compounds will be characterized by cryogenic, matrix-isolation EPR and electronic spectroscopy. Another aspect of the research will employ photoacoustical calorimetry to acquire thermochemical data on strained bridgehead olefins and imines via the enthalpies of their photochemical generation and subsequent reactions. %%% This grant from the Organic Dynamics Program supports the research of Professor Gary J. Snyder at the University of Chicago. Molecules in their lowest energy state ordinarily have all of their electron spins paired. A simplistic view is that electrons normally travel in pairs, where one electron of the pair spins clockwise and the other spins counterclockwise. In this research project, molecules will be prepared where the lowest energy state has either two or four unpaired electrons. That is, electrons that do not travel in pairs, which usually defines a higher energy state of a molecule. Specially designed molecules will be prepared to have these so-called high-spin states and their electronic and physical properties will be studied. This may be of practical importance to the preparation of organic ferromagnetic substances.
