“Edge-on” orientation of alkyl chains on an iodine-covered Au(1 1 1) surface studied by infrared reflection absorption spectroscopy

The edge-on orientation of alkyl chains, in which the carbon zigzag plane is perpendicular but the chain direction is parallel to the substrate surface, has been detected for specially designed 9,9-dioctadecylfluorene (DOF) molecules on an iodine-covered Au(1 1 1) surface by infrared reflection absorption spectroscopy (IRAS). Using p-polarized light, the methylene symmetric stretching vibrational mode with transition dipole moment μ parallel to the carbon plane has been observed predominantly at 2852 cm−1 compared to the methylene antisymmetric stretching mode with μ perpendicular to the plane.