A well-ordered assembly of tridodecylamine (TDA) molecules at the liquid-solid interface has been studied using scanning tunneling microscopy (STM). A significant effect of the applied tunneling bias voltage on the contrast of the amino group was observed in the STM images. In addition, benzoic acid molecules were found exclusively adsorbed onto the TDA assembly at the sites of the amino groups. The observation reveals the feasibility of template-directed adsorption of functional organic molecules with the aid of molecular assemblies.