Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms-B Program of the Division of Chemistry, Dr. Nancy Mills of Trinity University will examine the factors that affect delocalization by modification of antiaromatic dications and dianions. Antiaromatic species have been shown to be more sensitive to factors affecting delocalization because of their inherent tendency to avoid delocalization which results in an increase in antiaromaticity. For example, by annulation of a variety of polycyclic aromatic compounds to a cyclopentadienyl cation, the tension between the energetic advantages of delocalization of positive charge versus the stability from the intact polycyclic aromatic compound can be probed. Antiaromatic dianions are also accessible experimentally. Initial studies suggest that they are more antiaromatic than corresponding dications. Varying the position of benzannulation of a cycloheptatrienyl anionic system can again result in differences in antiaromaticity through differences in patterns of delocalization.
Stability is one of the most important concepts in chemistry because all chemical reactions result in making the most stable molecules possible. There is a class of compounds, called antiaromatic, which have been suggested by theory to be particularly unstable. Needless to say, these compounds have not been carefully studied because of the anticipated difficulty in making them. However, a suite of these compounds was discovered in an attempt to make something else and have proven to be much easier to make and study than anticipated. Because they are still relatively unstable, they turn out to be very sensitive to changes in their structure. Just as some changes in a physical structure, like a house or an automobile, might be hard to see in the dim light of dusk, but be very visible in daylight, changes that are hard to understand in a molecular structure that is stable, become very visible in a less stable, antiaromatic compound. These studies will be carried out by undergraduate students, with an emphasis on students just beginning their study of chemistry. By engaging these students in research early in their academic career, they are in a better position to learn what aspects of science interest them the most, and to make choices in coursework to support that interest. They will be aided by post-doctoral researchers who are interested in teaching undergraduate students as a career. The workforce development inherent in training undergraduates and prospective faculty is the primary broader impact of the grant.
