Adsorption of pyridine to TiO2 anatase(101) 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 pi* 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. (c) 2005 Elsevier B.V. All rights reserved.