The Chemical Structure, Dynamics and Mechanisms Program supports the work of Professor Malcolm H. Chisholm of The Ohio State University for the investigation of metal-metal (where metal, M, is molybdenum or tungsten) quadruplly-bonded compounds. Particular emphasis is given to alpha-alpha'-linked thienyl units attached to the M2 center by carboxylate, thiocarboxylate or amidinate groups. The chemical synthesis and fundamental physico-chemical studies contribute to the "intelligent design" of metallated organic polymers that enhance device characteristics of organic photovoltaics, OPV, by spectral expansion. The electronic coupling of the M2 quadruply bonded centers is modified by controlling the distance between the two metal atoms, their orbital energy matching, conformation and/or chemical charge. These molecular systems can be viewed as molecular rheostats and rectifiers as they act as signals and switches to report on their environments and redox states. The electronic spectra of the complexes are studied by ultra-fast spectroscopy (femtosecond- and nanosecond-transient absorption, IR and Raman) to examine the charge delocalization as a function of time.
Sunlight is one of the few renewable energy sources available on a large enough scale to address the world's long-term energy needs. This research examines new chemical structures that are capable of capturing sunlight for further conversion into electrical energy. In collaboration with Professors Epstein in Physics and Berger in Electrical Engineering, the Chisholm group examines the use of the MM quadruply bonded complexes as light "harvesters" for solar cells and light emitting devices (LEDs). These metal complexes are modified and optimized to absorb large portions of the available solar light and to transfer this light into forms of energy that can be transported or stored. Undergraduate and graduate students interact with groups in physics, electrical engineering and material science. This multidisciplinary program provides an outstanding educational background for careers in science, particularly in the development of alternative energy technologies. Particularly noteworthy is the connection with the Ohio Photovoltaic Initiative for Commercialization which provides students with opportunities for internships and future employment as well as providing a ready platform for the commercialization of devices that arise from these fundamental laboratory studies.
The sun provides the energy to power our planet and is indeed responsible for sustaining life. Ultimate fossil fuels will be exhausted and we must come to rely on solar power for photon harvesting in the production of both electricity and fuels. Our research work focusses on what happens when light is absorbed by organic materials incorporating metal atoms. Upon phonton absorption these new materials, synthesized in our laboratory, promote an electron from the metal to the organic material. This may be described as a separated electron-hole pair. The lifetimes of these photo excited states range from 10-12 to 10-5 of a second and in this time it is possible to separtate the electron and hole and have them migrate to electrodes to form a photo current. We are working to fascilate this electric current by studying the factors that favor charge separation and electron-hole transport in organic media for the construction of flexible inexpensive photo-voltaic devices. We are also designing materials that will absorp light across the entire solar emission spectrum which will thus enhance our ability to utilize solar radiation more efficiently. Students trained in this research have received their doctorate degrees and gone on to the workforce in research in industry, government labs and into teaching positions in universities and 4-year colleges. They are experienced in chemistry and material science.
