Anchor group influence on molecule-metal oxide interfaces: Periodic hybrid DFT study of pyridine bound to TiO2 via carboxylic and phosphonic acid

Adsorption of pyridine to TiO2 anatase(1 0 1) surfaces via carboxylic acid and phosphonic acid anchor groups has been investigated using periodic DFT calculations. Stronger adsorption is observed for pyridine-4-phosphonic acid than for pyridine-4-carboxylic acid. Periodic molecular orbitals are visualized, and surface electron transfer properties are interpreted in terms of the orbital mixing. More pronounced electronic interactions of the π* level with the TiO2 conduction band is observed for the pyridine-4-carboxylic acid than for the pyridine-4-phosphonic acid. This suggests that surface electron injection times via the carboxylic anchor group can be twice as fast as via the phosphonic anchor group.