This CAREER award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports work by Professor Papish at Drexel University to synthesize and study new ligands and complexes; the goal is to mimic the structure and function of important metalloenzymes. In particular, the Papish group is interested in modeling phosphotriesterase (PTE) because PTE catalyzes the hydrolysis of both pesticides and nerve gases. New ligands will be designed to mimic the secondary coordination sphere and provide water-solubility, properties that should lead to fast catalysis of important hydrolysis reactions. The scope of potential research applications is large and includes modeling various esterases, carbonic anhydrase and oxygenases. Model complexes could provide catalysts for green chemistry applications, including the breakdown of environmental toxins, the harnessing of oxygen as an abundant and environmentally benign oxidant, and the development of a class of ligands that is compatible with water as an alternative to the use of organic solvents. This research project will be used as a means of educating and motivating high school, undergraduate and graduate students to study science by directly involving students in the research. To illustrate that science and research are viable career paths for currently underrepresented groups, a workshop on 'Careers in Chemistry' that features women and minority chemists will be established. This workshop will create an informal network of peer and professional role models for students; members of this network can serve as mentors. In addition, they will describe the series of decisions that led them to become successful scientists.
Our NSF sponsored work led to the development of new tripodal ligands that can be tuned by hydrogen bonding interactions and protonation. Specifically, we synthesized and studied bulky tris(triazolyl)borate (Ttz) and other new tripodal N3 donor ligands that offer protonation sites in metal complexes. Reactivity studies led to two important accomplishments. 1) Protonation of the CuI bound Ttz ligand changes the catalytic reactivity and increases yields of C-H activation products; this new approach to C-H activation shows the intellectual merit of our work. 2) Ttz protonation in CuII complexes changes the redox potentials and can facilitate biomimetic nitrite reduction. Our bioinorganic Ttz work resulted in 10 published and 2 manuscripts. This demonstrates our experience with using earth abundant first row metals for catalysis. The de novo design and synthesis of ligands that place hydrogen bonds near the metal center was an explicit goal of my NSF CAREER proposal, and some of the new ligands (including 6,6’-dihydroxybipyridine) have found a multitude of unanticipated uses. Organometallic hydrogenation studies have become a promising application of the ligands designed with NSF CAREER support. Eight publications (6 papers and 2 patent applications) have involved catalytic transfer hydrogenation and anticancer applications. Three publications and one patent have resulted from water oxidation studies using Ir, Ru, and Cu catalysts. Hydrogenation and water oxidation reactions use ligands that provide hydrogen bonds or sites for protonation and deprotonation. Intellectual Merit of Work Done with NSF Support - In summary, 18 papers (plus 2 that are to be submitted) and 2 patent applications in total resulted from NSF support. All of these studies used hydrogen bonding or proton responsive ligands, but they clustered around three themes: biomimetic inorganic chemistry, hydrogenation, and water oxidation, with the last area being a recent focus of work in my group. Most of these papers have been published in high impact journals and have been highly cited; three of our papers were in invited issues. The use of Ttz ligands in proton responsive metal complexes has allowed the Papish group to develop new approaches to catalysis of nitrite reduction and C-H activation. These developments have been well received in the community, with the PI receiving invitations to speak. Most notably, water oxidation studies with dhbp complexes made the cover of Inorg. Chem., and on this topic and related hydrogenation reactions we filed a patent. Our iridium water oxidation precatalysts are among the most active catalysts in the literature, as described by us and others. Broader Impacts of Work Done with NSF Support - The Papish group has included 20 undergraduates (UG), 7 MS students, 6 PhD students, and 4 postdoctoral scholars during the period of NSF CAREER support (at both Drexel U. and University of Alabama, some of whom received university support). The group has been diverse, at 49% female and 12 % underrepresented minorities, with diversity at all levels. Three NSF REU supplements have funded six summer research experiences, which included two students that did their summer research as part of a spring-summer co-operative work experience and one public school teacher’s summer research experience. Two REU students were from LaSalle and Villanova Universities which are primarily undergraduate institutions. Education and motivation of students through research has been successful (13 papers with UG coauthors, many as lead author) and of the 8 Papish group UGs that have gone on to graduate school 3 have already received PhDs. In 2013, Dr. Papish and Lauren Reuther, a former UG student, were honored with the ACS Division of Inorganic Chemistry’s Award for undergraduate research, awarded in part due to Lauren’s contributions to two papers in which she performed thermodynamic acidity measurements and further analysis in a highly creative and independent fashion. Lauren presented her research at the fall 2013 National ACS meeting where she received her award. The PI has also mentored those outside our group that are interested in science. The PI hosted at Drexel University two Workshops on "Careers in Chemistry" and one seminar that featured academic, industrial, and alternative career scientists, and allowed the invited students (at the HS, UG and graduate levels, from Drexel and 15 area colleges) sufficient time to network with the scientists. The workshops included an audience (~40 students at each event) of which 46% self identified as being "underrepresented in science". Dr. Papish has spoken at local high schools and gave a workshop twice at the "Catalyst" conference for middle school girls, hosted by Swarthmore College (in total impacting ~100 students). Dr. Papish published a book chapter in "Tips on Getting an Academic Position." In 2011-2012, Dr. Papish hosted a seminar series supported by Drexel University on "Big Picture Issues: Green Chemistry and Sustainability" which discussed how inorganic chemistry targets these issues; this series featured prominent scientists and invited local students to gain career advice from them.
