Investigating Copper-Thiophene Binding Interactions: Impact on the Desulfurization of Hydrocarbon Fuels by Adsorption Processes John T. York, Department of Chemistry, Stetson University The binding of thiophene and benzothiophenes to copper(I) centers is an important step in adsorption processes in which copper salts remove sulfur-containing impurities from petroleum fuels. We are using both density functional theory and synthetic chemistry to help understand factors that affect bonding in organometallic copper-thiophene complexes. To determine the impact of ligand basicity on the binding of thiophene to copper(I) centers, DFT calculations were performed on [(L)CuI(thiophene)]+ adducts where L = substituted 1,10-phenanthroline ligands. Figure 2. DFT-calculated variation in [(L)Cu]+- thiophene interaction energy with ligand pKa. Energy decomposition analysis (EDA) methods, which calculate total interaction energy between the [(L)Cu]+ fragment and thiophene, predict that increasing ligand basicity will reduce overall favorable interactions between the two fragments, largely due to the lowering of favorable electrostatic attractive forces (Figure 2). This knowledge could have important implications in the design of materials for adsorption processes. Figure 1. DFT-optimized geometries of [(L)Cu(h2-thiophene)]+ complexes.