In this project supported by the Chemical Structure, Dynamics, and Mechanisms Program of the Division of Chemistry, Professor Jochen Autschbach of the University at Buffalo, State University of New York, and his research team will develop theoretical models for the calculation of nuclear magnetic resonance (NMR) spectra, and for circular dichroism (CD) spectra and optical rotatory dispersion (ORD). This work will advance our understanding of structure-specific NMR parameters, and the structural and electronic origins of the chiro-optical response. In addition, the influence of the chemical and physical environment on these molecular properties will be explored.
This research will not only advance our understanding of the relationship between molecular structure and measured spectra, but also our general understanding of the interaction of light and matter. Theoretical methods and software developed during this investigation will be made available to the larger community of scientists. In addition, this research project will be a vehicle for the training of graduate and undergraduate students. The student experience will be enhanced by the collaborative nature of the project; while the work within the Autschbach group is computational, it will be done in the context of collaborations with experimentalists from a variety of fields, including materials science and catalysis.
In this research project we use high-performance computing to calculate, from first principles, how molecules and nano-scale systems interact with light (visible, ultraviolet, or infrared) or electric and magnetic fields. The calculations use quantum mechanics to describe how the electrons in a molecule respond to the presence of light and field (hence the word 'response' in the project title). These interactions can also be probed experimentally, which give rise to science's most powerful experimental tools that tell researchers about chemical bonding in molecules and the geometric shapes of molecules. The intellectual merit of the research project is the prediction of interactions with electromagnetic fields for specific classes of molecules for which the molecular geometries or bonding are not known or debated, and for which knowledge of their geometries or their chemical bonds would be very important. The idea is that we can computationally predict the outcomes of experimental measurements for different possible geometries or bonding scenarios, and experimentalists can then check which prediction matches the experiment. Another facet of the research is explaining experimental measurements after the fact, in order to confirm that they are properly understood and interpreted. A third aspect is to develop a better fundamental understanding of molecule - field interactions, i.e. what makes them strong or weak, or why does an observed effect have a certain sign and not the other. Prime examples that have been studied with support from this grant are catalysts and co-catalysts for which molecular geometry and reactivity are often poorly understood but it would have tremendous economic impact if they could be improved in a rational design process. Other examples that were studied during this project are platinum complexes with anti-tumor activity. Here, we showed how the geometry of the complexes dictates the outcome of magnetic resonance experiments. It may be possible to use this information and learn to monitor how the structure of the complexes change as they react with DNA and other molecules. A third sub-topic focused on the interaction of carbon nanotubes with magnetic fields, to learn on how these interactions depend on the tube structures. We also have a very active collaboration with an experimental group on the optical properties of organo-metallic complexes with helical organic groups. When synthesized, these molecules come in pairs that are mirror-images of one another with different optical properties, and they can be separated into samples containing pure forms of these mirror images. The technical terms are that these molecules have a 'handedness' ('chirality', from the Greek word for hand, as our left and right hands are mirror images of one another and nor ) and can be separated into two distinct enantiomers with different 'chiro-optical' properties. Most bio-chemically active molecules are also chiral. The principal investigator maintains a web page at http://ja01.chem.buffalo.edu/~jochena/research/opticalactivity.html explaining chiro-optical effects to non-specialists. Potential applications of the organometallic complexes that we are studying are in optical materials that require strong chiro-optical effects. The broader impacts of the project are as follows: New theoretical methods were developed for calculating interactions between molecules and electromagnetic fields, and to improve the accuracy of such calculations. These are available to other researchers and the public in the free open-source quantum chemistry package NWChem (www.nwchem-sw.org/index.php/Main_Page) of which the principal investigator is a co-developer, and in other quantum chemistry software packages. Our developments of new theoretical methods contribute to the scientific software infrastructure in general and are used by chemists, bio-chemists, physicists, and material scientists. Some of our research has implications for bio-medical research, catalysis, and materials research. In-depth training in science, technology, engineering, and mathematical (STEM) fields is widely recognized as a crucial asset for any advanced nation in the 21st century. The training of a research scientist is not done via lectures, on-site or on-line. Rather, this training is more like a hands-on apprenticeship where the student learns from observing others who master the trade. The PI and his group contribute actively to this endeavor, by training next generation scientists in the laboratory and by providing research experiences for undergraduate students. Furthermore, the PI's outreach and his numerous contributions to the chemical education literature help to train the next generation of scientists as well as school teachers who educate our children.
