The complexation of Fe-II and Cu-II ions by phenanthroline and terpyridine-based Langmuir films was studied by the effect the added ions in the subphase on the isotherms. We found that CuII had a pronounced effect on the isotherm consisting of phenanthroline moieties forming a square-planar 1:2 (Cu-II/phenanthroline) complex. However, Fe-II affected the isotherm made of 1:1 phenanthroline/terpyridine amphiphiles as a result of forming a pentacoordinate complex.