Designing Enhanced Dispersion Force Effects Into Inorganic and Organometallic Molecules

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The Chemical Synthesis Program of the Chemistry Division supports the project by Professor Power. Professor Power and his group are developing new classes of compounds to demonstrate the interaction of the groups (ligands) within a metal complex. The new compounds differ from those currently known because they are designed to display enhanced attractive London Dispersion Forces(LDFs) between molecules. London Dispersion Forces strengthen the bonding and hence the stability of their extended structures. The London Dispersion Forces describe interactions between molecules rather than interactions between two atoms (covalent bonds). To date, such forces have not generally been incorporated into molecular design. The project is aimed at obtaining a fundamental understanding of how such forces can be manipulated and exploited in chemical synthesis. The project lies at the interface of inorganic, organic, and organometallic chemistry. A variety of spectroscopic, structural, and computational techniques are used to characterize the new compounds obtained. Besides training in synthesis, the project exposes students to a variety of physico-chemical and theoretical methods. The research project also includes outreach activities designed to broaden the participation of underrepresented minorities in scientific research.The basic scientific objective of the research is to design enhanced London Dispersion Forces into molecules so that their effects can be calculated, measured, and used to synthesize previously-unknown classes of molecules. The Power group plans to focus investigations on alkyl boranes with rigid hydrocarbon substituents derived from inexpensive natural products. They have already shown that the extended structures display Lewis acidic properties very different from regular alkyl boranes as a result of the attractive London Dispersion Force interactions. In addition, the Power group investigates a variety of disproportionation and dissociation reactions in both the main group and transition elements that are strongly influenced by LDF. Examples involve the synthesis of the first stable, two-coordinate copper(II) derivative. Normally, low-coordinate copper(II) compounds are unstable due to auto-reduction to copper(I) species or copper metal. Using a ligand that favors LDF interactions, the reverse reaction, auto oxidation, occurs so that a stable two-coordinate copper(II) species is obtained from a copper(I) starting material. A similar effect enables the synthesis of the first two-coordinate vanadium(II) compound. The investigations have also shown that LDF effects are important for the multiple-bonded heavier main group compounds, where such effects usually exceed the weak element-element bonding. LDFs are responsible for the stability of numerous multiple bonded heavier main group compounds. Undergraduates, graduate students, and post-doctoral fellows are supported through this award. The knowledge gained may be fundamental to our understanding of bonding and how more complex structures are built.