The Art of the Chemical Bond

Chemical bonding enables scientists to take the 100-plus elements of the periodic table and combine them in myriad ways to form chemical compounds and materials. The success rate is pretty good, as more than 120 million chemical substances are currently registered by CAS, a division of the American Chemical Society. But there are still hundreds of millions more waiting to be created. Researchers continue to find new ways to get atoms to interact and stick together. They also continue to evolve methods for breaking and re-forming bonds during chemical reactions to improve on the synthesis, properties, and performance of existing chemicals and materials. For some, the work of scientists who spend most of their time thinking about chemical bondingboth the wellseasoned principles and newly discovered aspectscan seem mystifying. Taking a deeper look at what these scientists and engineers do and how they go about doing it, from thought experiments to developing their own computational software, can be illuminating. “Chemical bonding is the language of logic for chemists,” according to Anastassia N. Alexandrova, a theoretical and computational chemist at the University of California, Los Angeles. Some researchers spend their time developing bonding theories, and for that you need a strong background in quantum mechanics, Alexandrova says. They have little time to think about synthetic chemistry. In contrast, other researchers focus on computational methods and may spend a lot of time thinking about synthetic chemistry and not so much on quantum mechanics. Experimentation is the essential leveling point between these two camps, Alexandrova says. “It is often the place to start and always the final goal.” She describes her research as being in the middle ground. “Our group uses existing observations to build knowledge and develop theory that allows us to make testable predictions,” Alexandrova says. “Along the way, we might develop new computational methods, but only as a by-product to assist the chemistry. Once we have sufficient understanding, we start manipulating the devised system, and this is the culminating moment, to see if we are getting somewhere new. This is where we provide a service to the rest of the chemistry community.” In July, Alexandrova cohosted the International Conference on Chemical Bonding (ICCB) in Hawaii, an annual conference she cofounded and co-organizes with Alexander I. Boldyrev of Utah State University. The meetings bring together theorists, computational chemists, and experimentalists who probe new ways of manipulating bonds as they seek out means to improve on chemical synthesis, materials design, and property analysis.