Mentor: Prof. Jonas Goldsmith
It is possible to functionalize various surfaces by attaching various different types of organic ligands to them. The organic ligands are able to form complexes with transition metals, and an electrode composed of the surface material in question is placed into a solution containing a low concentration of the aforementioned metal complex. The interactions of various ligands with metal and carbon surfaces can be analyzed electrochemically, and in this manner the rate at which these ligands adhere to the surface, based on varying concentration, can be examined.
During this summer research period, we will synthesize 4-methyl-4-(5-bromobutyl)-2,2’-bipyridine and 4-methyl-4-(5-bromononyl)-2,2’-bipyridine. The alkyl halide will be replaced with an amine group (see Fig. 1), and then an amide group (see Fig. 1) attached to a polyaromatic moity, such as pyrene, as seen in figure 3. The purity of each synthesized compound will be determined through Nuclear Magnetic Resonance and Mass Spectrometry. Due to the nature of the experiments, it is necessary that each step of the synthesis produce a particularly pure product. We will then complex this molecule with a transition metal, such as cobalt or ruthenium, as seen in figure 3. Due to the chelate effect, the preference for the formation of a transition metal complex with a bidentate ligand, the bipyridine molecule will form particularly strong complexes. The extended pi electron system which the polyaromatic group possesses will cause it to adsorb strongly to a graphite surface, which has a similar extended pi electron system. Due to this affinity for adsorption, we can use a graphite electrode to observe this process.
We will also examine, electrochemically, the interactions of 4-methyl-4-(5-thiobutyl)-2,2’-bipyridine and 4-methyl-4-(5-thiononyl)-2,2’-bipyridine with gold surfaces. The thiol group (see Fig. 1), which, as with the amine group, replaces the alkyl halide, has strong affinity for gold surfaces. This affinity will cause the thiol group to adsorb strongly to the surface of the gold electrode, and we will be able to examine the interactions of transition metal complexes containing this ligand, as shown in figure 2, with a gold electrode.