Effect of the metal on the organization of tetraamidometallophthalocyanines in Langmuir-Blodgett films

Metallophthalocyanines (MPc's) [M being one of the following metal ions: Co(II), Ni(II), Cu(II), or Zn(TT)], bearing amide side chains and being highly soluble in organic solvents, have been synthesized by starting from the corresponding phthalonitrile. All four compounds can form Langmuir and Langmuir-Blodgett films, but interestingly, their behavior as monolayers was shown to be very much dependent on the central metal ion. The study of Pi-A isotherms, low-angle X-ray diffraction patterns, and IR dichroism allowed us to elucidate these behaviors, Cobalt and zinc phthalocyanines are coordinated with water molecules and therefore orient with art angle of around 60 degrees with the normal to the air-water interface or to the substrate. On the other hand, nickel phthalocyanine is not coordinated with water; Pi-Pi interactions become possible, and the molecules can orient more vertically at the air-water interface; they form columns that orient in the transfer direction during the deposition process. Finally, the copper phthalocyanine is an intermediate ease. For low surface pressures, it behaves like Co and Zn compounds: the square planar copper(II) is certainly liganded with water molecules. At higher surface pressures, the water molecules are ejected and the macrocycles can orient more vertically (angle of around 30 degrees between macrocycle and normal to the air-water interface) and form oriented columnar structures when deposited onto substrates.