This award in the Chemical Synthesis (SYN) program supports work by Professor Lisa F. Szczepura at Illinois State University to carry out fundamental studies to determine the scope and mechanism of small molecule activation by octahedral hexanuclear metal complexes. The reactions of interest are [2+3] dipolar cycloadditions and nucleophilic additions involving nitriles, isonitriles, and azides. The reactivity of different terminal ligands will be investigated, and a study of the mechanistic aspects of these reactions will be performed. These investigations will result in a deeper understanding of the factors that influence small molecule activation by these cluster cores. In addition, these studies will help probe potential applications of octahedral cluster complexes as catalysts and as building blocks in new solid state materials. By incorporating successful concepts from the Enrichment Workshop Program, developed with funds from a CAREER award, into her mentoring and research efforts, the PI hopes to generate well trained, motivated, underrepresented scientists at the undergraduate and graduate levels. In particular, mentorship of freshman or sophomore students from groups that are underrepresented in the sciences will help increase the retention and success rate of these students at Illinois State University.
These studies will provide a better understanding of the activation of small organic molecules by transition metal clusters and will lend insight into the mechanistic aspects of this activation. Small molecule activation involves the formation of a number of fundamentally important compounds that play key roles in organic synthesis, and in a number of different industries including: pharmaceuticals, explosives, dyes and agriculture.
An important application of transition metal complexes is their use in aiding the transformation of small organic molecules for use in pharmaceuticals, plastics, flavors and fragrances. Most of the metal complexes currently employed as catalysts consist of single-metal systems. The Szczepura group works with multi-metal systems, often referred to as clusters since the metal atoms are closely grouped together in a regular fashion. Metal clusters containing transition metals (e.g. iron, copper, cobalt) have held a special place in inorganic chemistry because these systems have been shown to demonstrate unique reactivity compared to the more common single-metal complexes. In 2007, Szczepura and coworkers reported that some clusters containing six rhenium (transition) metals could activate small molecules to react. Intellectual Merit. The aims of this grant were directed at exploring the scope and mechanism of small molecule activation by rhenium based clusters with a focus on addition and cycloaddition reactions. Different methods that could be used to remove these rings from the metal center were also examined. Towards this end, a total of 16 new cluster complexes were prepared and studied. The results obtained demonstrate a number of novel reactions taking place at the cluster core. These studies provided a much better understanding of the chemistry of these cluster complexes which may one day enable the use of these systems in applications such as catalysis. In addition, the ability of these complexes to luminesce (emit light upon excitation) was also investigated. While rhenium based clusters have been known to display this property, some interesting interplay between the new cycloaddition products and the light-emitting properties of the clusters was discovered. Broader Impacts. The Department of Chemistry at Illinois State University does not offer a doctoral program in chemistry. Therefore, training students is an important aspect of this research because all data is collected by BS and MS level students. Professor Szczepura makes an effort to train and mentor students from diverse socioeconomic backgrounds in her research group. Three MS students worked on the research described above. One of these graduates is now working in the chemical industry and the other two are pursuing doctoral degrees. Eight undergraduate students have also gained substantial laboratory experience by working on the research described above. Four of these have made significant contributions to the scholarly outcomes of this award. Of those students who have graduated, all but one are pursuing an advanced degree in chemistry. In addition, another six undergraduates who are considered underrepresented minorities (African American, American Indian and Hispanic) were mentored through this project. Notably, many of these students conducted experimental research and all but one has graduated (or is on track to graduate) with a degree in science.
