Elaboration of Petroleum-Derived Aromatics for the Generation of Conjugated Discotic and Cruciform Structures: Controlling Electronic Properties via Transition Metal Coordination

Reports: UNI1 50058-UNI1: Elaboration of Petroleum-Derived Aromatics for the Generation of Conjugated Discotic and Cruciform Structures: Controlling Electronic Properties via Transition Metal Coordination

Nathan P. Bowling, PhD, University of Wisconsin (Stevens Point)

Our research is motivated by a desire to generate conjugated organic molecules that will complex to select transition metals (Ag(I), Cu(I), Pd(II)), forming metallorganic frameworks with unique electronic properties. At the heart of this project is the development of a novel aryl-ethynyl ligand (1) with coordinating pyridine moieties. This target has been generated and studied by two students. The details of its synthesis and preliminary observations of its complexation behavior were presented by one student at the 2009 American Chemical Society Midwest Regional Meeting and at the 2010 UWSP Undergraduate Research Symposium. This student has now graduated, and is seeking employment in chemical industry. Our current focus, in this project, is to generate greater amounts of material so that we may better characterize the complexation behavior and electronic properties of this system. A second student, who desires to attend medical school upon graduation, is busy scaling up reactions, optimizing yields and attempting to grow crystals of a metal complex (1-M) similar to that shown above.

Using this small conjugated ligand as a building block, we desire to synthesize large conjugated systems that will accommodate multiple equivalents of a transition metal. The two separate types of conjugated molecules that we are interested in pursuing are discotic and cruciform motifs. These projects are synthesis heavy. As is common with these types of projects, my research students are frequently solving and uncovering synthetic challenges. In our attempts to generate discotic structure 2, for instance, we have been able to generate modest amounts of intermediate 2-I. Attempts at deprotection and subsequent coupling to a 3-halopyridine have led to, at best, recovered starting material, and occasionally no identifiable products. A junior student, who desires to one day become an M.D./Ph.D., is sorting out these issues.

To date, this award has supported the research projects of four undergraduate students. The fourth student (the other three mentioned above) has embarked on a journey to generate conjugated cruciform structures that will complex to transition metals (e.g. 3). Although this project is synthetically tedious, she has made astounding progress. The precise details of her successes and the many hurdles she has surmounted are beyond the scope of this report. With some luck, she will be able to report a complete synthesis of this compound by Spring 2010.