Molecular Electronic Effects on the Thermal Grafting of Aryl Iodides to TiO2 Surfaces

Abstract

Recent studies have shown that aromatic iodides can readily graft to hydroxylated surfaces of TiO2 and other metal oxides, forming a convenient route to molecular functionalization of metal oxides. While these reactions appear similar to the Williamson ether synthesis of organic chemistry, the SN2 mechanism typically invoked in solution phase reactions is less accessible on surfaces, and the mechanism of the surface reactions is poorly understood. We have undertaken a combined experimental and computational study in an effort to understand how the molecular electronic structure impacts the surface reactivity. Computational studies of reaction enthalpies were compared were used to generate Hammett plots that were then compared to experimental measurements of surface grafting rate for molecules with different substituent groups. Our results show that there is poor correlation between Hammett parameters and surface reactivity. Additional experiments were conducted to evaluate the impact of molecular hydropho...