Our research is focused on the synthesis and characterization of organometallic models for the active site of the hydrogen producing enzyme, [Fe-Fe] hydrogenase. In the summer, two undergraduate students worked on the synthesis of new models. This was a continuation of work they did during the academic year. Significant progress has been made on this project.
The students synthesized several thiol ligands and used them to make novel diironhexacarbonyl complexes. Our design of [Fe-Fe] hydrogenase models incorporates electroactive groups (Naphthalimides). We are exploring the use of substituents on the naphthalimides to modulate the electronic and electrochemical properties of the compounds. We have successfully prepared eight new models. The synthesis and isolation of these compounds involved the use of Schlenk line techniques and provided a good opportunity for the students to learn how to do air-sensitive chemistry.
After preparation and isolation, the compounds were characterized using spectroscopic and electrochemical methods. Infrared spectroscopy was used extensively for the identification of the complexes. IR peaks corresponding to the stretching frequencies of terminal metal carbonyls were recorded for all of the compounds between 2000 and 2100 cm-1. The potential of these compounds as hydrogenase mimics have been explored by cyclic voltammetry. The results indicate that these complexes effectively catalyze the electrochemical generation of hydrogen at modest potentials.
Preliminary results of this study were presented by the principal investigator and students at the national ACS meeting in Anaheim CA (March 2011) and the Georgian Bay International Conference on Bioinorganic Chemistry, Parry Sound-Canada (May 2011). The PRF grant provided support such as summer stipend to two students and travel funds to one student to attend the ACS conference. Some pieces of equipment (rotary evaporator and vacuum pump) were purchased for use in this project. The principal investigator and students are deeply grateful for this support that has been crucial for starting a productive undergraduate chemistry research program at Arkansas Tech University.