The Organic and Macromolecular Chemistry Program in the Chemistry Division at the National Science Foundation supports Professors Devens J. Gust, Anna L. Moore and Thomas A. Moore of Arizona State University for a research project that involves the synthesis and study of complex molecules consisting of covalently linked chromophores, electron donors and acceptors, and photochromic molecules that change their structure upon exposure to light. Each of these components can exchange information with others via intramolecular energy and electron transfer. It is these interactions that will allow complex phenomena to emerge. Several different classes of molecular systems have been identified as most promising for study. In one of these systems, Professor Gust and his collaborators will design, synthesize, and spectroscopically investigate molecules that absorb light and convert it to electrochemical energy in the form of a charge-separated state, as occurs in photosynthetic reaction centers. In another, "molecular triodes" and related structures will be studied. In these, a light-induced output such as fluorescence or photoinduced charge separation will be modulated by a second wavelength of light that is also absorbed by the molecule. These molecules will be analogs of electronic triode amplifier tubes or transistors, and their design will challenge our understanding of the factors influencing intramolecular energy and electron transfer. And finally, it has been recently demonstrated that the earth's magnetic field affects the lifetime of biradical states formed by light-induced intramolecular electron transfer. This discovery may help uncover how birds and other mammals can navigate using the earth's magnetic field. However, the chemical basis of the observed effect is not yet understood. Professor Gust and collaborators will prepare and study new molecules designed to uncover the mechanism in collaboration with researchers at the University of Oxford.
Broader impacts of the proposed research will be results that lead to a better understanding of emergent phenomena, a topic that cuts across many fields of chemistry, physics and biology. The research will involve students at the undergraduate, graduate and postdoctoral levels. Of special importance is the training of students from groups traditionally underrepresented in chemistry. Some of the recruiting and training will be in collaboration with several units of WAESO, (Western Alliance to Expand Student Opportunities), an NSF-LSAMP program centered at Arizona State University. Additionally, formal and informal programs for exchange of research students will be instituted with several Latin American universities. Experience has shown that highly-talented, successful students from Latin America serve as excellent role models for domestic Hispanic students, giving them the guidance and confidence necessary to achieve their potential. Informal student exchange programs with several European universities are currently in place, and will be continued and expanded in the new project.
The purpose of this research was to investigate some of the complex phenomena that occur when small functional molecules are chemically joined to form larger molecules. When linked together, the smaller molecules can interact with each other, permitting interesting and useful new properties to emerge. Two areas were investigated. In the first, photochromic molecules that change color when exposed to light were combined with other molecules to create larger "supermolecules" that can be used to manipulate data using light. This work may lead to new methods for data processing and transmission. Related molecules were shown to act like light-driven molecular transistors, and these results may lead to new methods for visualizing proteins, cells, etc., in medicine and biology. The second area of research involved a collaborative study on how birds use magnetic fields to navigate. The birds act like they have molecular compasses. In the research, we learned how to make molecular systems that change their properties according to the magnitude and direction of weak magnetic fields. This research may lead to a fuller understanding of how birds and other organisms navigate. Much of the research was carried out by graduate students and postdoctoral students. These men and women learned how to become better, more creative scientists, and will apply their new skills when they enter the workplace or find new jobs in science.
