Orientation of carboxylates on TiO2(1 1 0)

C K-edge NEXAFS has been used to examine the orientation of formate, acetate and propanate in their 2×1 overlayers on TiO2(1 1 0) at 300 K. These data indicate that the carboxylate planes are more or less perpendicular to the surface. The off-normal tilt angles from NEXAFS are 20±10°, 0±5° and 14±10° for formate, acetate and propanate, respectively. The corresponding apparent twist angles out of the [0 0 1] azimuth are 29±10°, 26±5° and 39±10°, indicating a bond geometry essentially independent of the alkyl chain length. The apparent twist angles probably arise from averaging of majority and minority species.