Spectroscopic Studies of Partially Bound Lewis Acid-Base Complexes

The Experimental Physical Chemistry Program supports Ken Leopold of the University of Minnesota-Twin Cities Campus in his Fourier-transform microwave (FTMW) spectroscopic studies of the structural and electronic properties of Lewis acid-base complexes. In these studies, he will focus on complexes in which the donor-acceptor bond is only partially formed, i.e., a bonding regime intermediate between van der Waals and chemical interactions. In previous work, Prof. Leopold observed that gas phase species which lie in the intermediate regime between van der Waals and chemical bonding undergo enormous changes in structure upon crystallization. In these studies, he will (1) extend this work to a wider number of complexes to investigate the effects of Lewis acidity and basicity on the nature of the donor-acceptor bond, (2) measure dipole moments of partially bonded molecules, and (3) characterize larger clusters containing a partially bonded unit. Partially bonded species are important in a variety of areas of chemistry. One of the most interesting aspects of partially bound systems is their hypersensitivity to a surrounding medium. The phenomenon is most apparent when comparing gas phase species with their crystalline analogues. These studies will provide an experimentally grounded complement for a growing body of theoretical work aimed at further understanding the nature of the electron pair donor-acceptor bond.