Sharp J-Bands Observed for Xanthone Derivatives in Langmuir and Langmuir–Blodgett Films

The first shorter-molecular-axis polarized electronic absorption band of 7-methylxanthone-2-carboxylic acid octadecyl ester shows a surface pressure dependence in Langmuir films, giving rise to a so-called J-band at higher surface pressures. In contrast, 7-methoxyxanthone-2-carboxylic acid octadecylamide in the Langmuir film exhibits the J-band even at low surface pressures. AFM images of the LB film of this amide show that the alkyl chains are regularly arranged with a spacing of 0.67 nm in accordance with the head-to-tail arrangement of the shorter molecular axes of the xanthone skeleton.