A Mixed Fullerene-Ferrocene Thermotropic Liquid Crystal: Synthesis, Liquid-Crystalline Properties, Supramolecular Organization and Photoinduced Electron Transfer

Grafting of a ferrocene-containing liquid-crystalline malonate derivative to C₆₀ led to the mixed fullerene-ferrocene material <b>1</b> which gave rise to a smectic A phase. Cholesterol was used as liquid-crystalline promoter. X-ray diffraction experiments and volumetric measurements indicated that <b>1</b> is organized in double layered structures. The corresponding supramolecular organization within the mesomorphic lamellar phase is characterized by a microsegregation of the different units (ferrocene, fullerene, and cholesterol) in distinct sublayers. In such a smectic A phase, C₆₀ imposes the arrangement of the other molecular moieties. Photophysical studies revealed that electron transfer occurs from the donor ferrocene to the electron accepting fullerene. The formation of a long-lived radical pair, with lifetimes of the order of several hundred nanoseconds, was confirmed by time-resolved spectrometry, especially in the near infrared region, in which the radical anion of the fullerene moiety displays its characteristic fingerprint absorption.