The chemistry of metal-diselenolene complexes

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The combination of ligand non-innocence and reversible redox behaviour of metal-dithiolene complexes results in unique electrical, optical, magnetic and conductive properties. Because of these properties dithiolene-containing complexes have been investigated for potential use in the partitioning of spent nuclear fuels, the purification of olefins in the production of polymers, dye-sensitized solar cells, catalysts for the photo splitting of H2O, magnetic materials, chemical microsensors, optical limiting devices, and more recently in the treatment of cancer.Thus, given the rich and diverse chemistry of dithiolene complexes it is not surprising that they remain a subject of high interest. While past research has shown parallels in the chemistry of diselenolene and dithiolene complexes significant difference also exist which warrants further research into diselenolene complexes. However, diselenolene complexes have not been as well studied either experimentally or theoretically. Indeed, a quick search of 'diselenolene' on ISI web of knowledge generates 38 hits whereas a search for 'dithiolene' results in 1,347 hits. Yet, the search for such Se-containing ligands has been active since the 1970s.Hence, using a combination of computational tools the role of these diselenolene complexes in bioinorganic chemistry as well as in materials science will be investigated. In particular, density functional theory (DFT) will be used to investigate the structures, reduction potentials and HOMO-LUMO gap energies of diselenolene complexes. Using time-dependent DFT the photochemistry of diselenolene complexes will be examined. Notably, mixed ligand diimine-metal-dithiolene complexes have been investigated for use in dye-sensitized solar cells and to the photo splitting of H2O to form H2. Regarding dithiolene containing enzymatic systems the biomimetic diselenolene analogues will be investigated using a combined quantum mechanics/molecular mechanics (QM/MM) approach. Natural bonding orbital (NBO) analyses will be performed to provide greater insight into the effect of substituting the S with Se on the electronics of the system.It is noted that with the depletion of fossil fuels it becomes more important for the design of new compounds that can convert solar energy into electrical or chemical energy. Moreover, from the continued burning of fossil fuels the production of CO2 continues. Thus, the design of new catalysts to be used in the sequestration of CO2, is also critical for our future. Importantly, the knowledge gained from this research program will provide insight into chemistry of diselenolene complexes that will lead to the design of new diselenolene containing components for use in dye-sensitized solar cells, catalysts for olefin purification, catalysts for the renewable production of H2 via the photocatalytic splitting of water and the catalytic reduction of CO2 to formate.