Fullerene- and porphyrin-appended crown ethers: Synthesis and preparation of stable Langmuir and Langmuir-Blodgett films

The synthesis of a series (1–5) of fullerene and Zn(II)-porphyrin amphiphiles with polar dibenzo[24]crown-8 headgroups is described. Their ability to form Langmuir monolayers at the air-water interface was investigated in a systematic study. The Langmuir films were characterized by their surface pressure versus molecular area isotherms, compression and expansion cycles, and Brewsterangle microscopy. Complexation of larger alkali metal cations (K⁺ and Cs⁺) by the polar headgroups leads to higher molecular area requirements and a better anchoring to the aqueous subphase. The monolayers of the porphyrin-(dibenzo[24]crown-8) conjugates were transferred as Langmuir—Blodgett films onto glass slides and the films characterized by UV-vis spectroscopy and grazing-incidence X-ray diffraction. Good evidence was obtained that the porphyrin-fullerene-crown ether triad 5 adopts a sandwich geometry in the LB films. In such an arrangement, the electron-attracting carbon sphere benefits from attractive interactions with the sandwiching electron-rich porphyrin and crown ether chromophores. The described films could have potential applications as functional materials in optical and electronic technology.