Incorporating MM Quadruple Bonds (M = Mo, W) into Organic Conjugated Pi-Systems. Fundamental Studies and Applications

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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.