Roald Hoffmann is supported by the Macromolecular, Supramolecular and Nanochemistry Program in research that melds chemical and physical approaches to the prediction of new structures, properties and reactivity across the periodic table, and especially matter under extreme conditions of pressure. The problems being explored range across all of chemistry, from hydrogen to astatine. In the realm of high pressure, the work is exploring the possible stability of SiO (not familiar quartz, SiO2), the potential superconductivity of species as diverse as AuO (with a so-called mixed valence transition between two forms of gold in the structure), and Li- or H-doped NbN, to molecular acetylenes and ferrocene under pressure. In order to gain further insight into the world in-between the molecular and the macro, the work is exploring the interplay of polarity and dimensionality in low-dimensional CdSe and NaCl arrays, looking at how to stabilize the silicon analogue of graphene, and exploring potential metallic micelles. Since prediction is the best test of understanding, the research sets out to design as yet unmade molecular and extended systems, including some nonclassical organometallics, untypical organoiodides, novel networks containing both tetrahedral and square-planar main group atoms, and the possible formation of O-O bonds in oxides.
Chemistry is to be found in the properties of persistent groupings of atoms, of molecules. From their changeable combinations comes the incredible variety of organic and inorganic chemistry at the center of the art, craft, business and science of chemistry. And moving out from this center one encounters the still greater richness of biological function and materials with unusual properties, as chemistry touches and affects the rest of the world. The molecular science continues to surprise in the shape of one molecule, in the reactivity of another, in the unusual electric or magnetic properties of a third. But we have a way to go to understanding, in the qualitative yet productive way chemists have of parlaying experience into the making of the new. The proposed research addresses this need for understanding, especially in the behavior of matter under pressures such as those at the center of the earth (attainable in a few laboratories as well). Addressing a range of bonding situations across the periodic table, from hydrogen to the actinides, this proposal uses quite specific bonding puzzles as a springboard to build frameworks of understanding that chemists and physicists can take away and themselves design new molecules and new extended structures (of the type found in minerals, diamond, metals). Such molecules might have interesting and important properties, high temperature superconductivity just one of them. Risky, specific, predictions of the existence of molecules and extended systems, and their structures and properties -- the best test of real understanding in chemistry is a hallmark of the work being performed.
