This CAREER award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports work by Professor John F. Berry at the University of Wisconsin - Madison to study the interaction of metal-metal multiply bonded groups with other metal atoms held in close proximity. A new class of coordination compounds will be synthesized that feature heterometallic interactions between a transition metal and an electron-rich metal-metal multiply bonded group. Donation of electron density from the metal-metal multiply bonded group will be probed using multiple physical methods with the aim of discovering new avenues for multi-electron redox reactivity promoted by these compounds. Chemical information will be collected and assembled into pedagogically useful data-based exercises in the form of computer-based hands-on learning modules as supplements to graduate and undergraduate coursework. These data will also be presented to the entirety of the chemical community in the form of an online interactive website or wiki.
Heterometallic interactions are important in multi-electron biological processes that are essential to life and are also of industrial importance from the standpoint of energy conversion. The discovery of new oxidative transformations that function via the use of molecular oxygen or hydrogen peroxide is relevant to improving the environmental impact of industrial-scale oxidative chemistry.
The focus of this project has been the discovery of new molecules in which two or more different metals are held together in close proximity. We have prepared a systematic library of novel heterobimetallic compounds and have explored how the identities of the metal atoms in these compounds affect their physical (colors, electronic, and magnetic properties) and chemical characteristics. Highlights include (1) the discovery of a new magnetic interaction between paramagnetic metal ions and a magnetically anisotropic metal-metal quadruple bond, (2) the discovery of unusual structural effects in which a change of ligands at one metal has an influence on the structure of a remote metal center, (3) preparation of thermally- and photolytically-sensitive heterometallic compounds with azide ligands, and (4) preparation of a compound containing all three of the Group 6 metals (Cr, Mo, and W). Additionally, novel molecules have been discovered that contain an oxygen atom attached to a bimetallic unit, a structural feature that had not previously been observed. This new complex is highly reactive and can undergo chemically reversible four-electron transfer reactions. As this compound is reduced, the oxygen atom becomes extremely basic and is able to react with ordinarily unreactive organic molecules, such as acetonitrile. We have also contributed to the theoretical description of metal-metal bonds. In this area, we have studied two types of compounds: (1) those having a closed shell metal-metal multiple bond, and (2) those having an open shell with multiple unpaired electrons that are spin-aligned due to the metal-metal interaction. This work has led to the training of three PhD chemists (to date), and one MS-level chemist. A number of undergraduate students were able to gain research experience in the Berry lab thanks to this award. Several of these students have gone on to graduate-level studies in chemistry or other science/engineering-related fields. New materials for the PI's graduate and undergraduate courses have been developed through this grant. A module exposing students to the use of the Cambridge Crystallographic Database is now fully integrated into the PI's graduate course, and modules about greenhouse gases and global energy use are now incorporated into the PI's undergraduate classes. The PI maintains a publicly-accessible database of diamagnetic correction factors that are extremely important for measurements of the magnetic properties of materials. This database is highly used, and highly cited.
