Ultrathin polymer films incorporating a ruthenium trisbipyridine (Ru) complex as an electron donor, and viologen as an electron acceptor, or a related redox pair, and their self-assembled monolayers were fabricated. Photochemical and/or photoelectric conversion using these film assemblies were carried out. The Ru complex incorporated in the polymer film showed a photocatalytic activity. Interfacial electron-transfer and electron accumulation were verified in the dye-polymer composite films.
Self-assembled monolayers of the Ru complex-viologen pair were fabricated on electrodes. The photocurrent efficiency profoundly depended on the donor-acceptor and acceptor-electrode distances as well as the donor : acceptor ratio. Multistructure assemblies using gold nanoparticles and supramolecular assemblies using surface sol-gel process were also proposed as photoelectric conversion devices.

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Photo-energy conversion is very important not only as a source of new clean energy, but also as a means of information processing. Several attempts were made to improve the efficiency of photoinduced charge separation by using interfacial electric fields of micelles and bilayer membranes, a good electron mediator, electron exchange reactions between redox chromophores aligned in molecular assemblies in aqueous solutions. Langmuir-Blodgett films have been employed to achieve unique properties such as amplified fluorescence quenching, anisotropic and molecularly controlled photoconduction. Photoresponsive thin solid films have been employed to achieve photon-mode super-resolution based on transient bleaching, ultrafast color changes due to photoinduced electron transfer reaction in ion-pair charge transfer complexes, ultrafast optical parallel processing based on complex refractive index changes in guided wave geometry consisted of a thin metal film and a thin polymer film containing organic dyes.

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The ready availability of [60] fullerene (C₆₀) and its homologues has increasingly invited exploration of their outstanding new physical and chemical properties. Among them, one of the most important applications is the medicinal use : for example, they act as a singlet oxygen (¹O₂) photosensitizer to cleave DNA and as an inhibitor to suppress the HIV protease activity. In spite of their high potentials, however, the applications have been very limited because of their poor water-solubility. Several lines of effort have so far been devoted toward compensation for this drawback, for example, by introduction of water-soluble substituents, mixing with water-soluble polymers, solubilization in γ-cyclodextrin (γ-CD), and water-soluble calix [8] arenes. We considered that among these methods, the host-guest method should be superior to others because (i) one can directly use “unmodified C₆₀” which can act as electron pool more efficiently than other C₆₀ derivatives, (ii) one can suppress undesired photo-dimerization of C₆₀ and (iii) dioxygen or substrates can collide with C₆₀ more efficiently. With these objects in mind, we designed a new water-soluble cationic homooxacalix [3] arene with a cone conformation. The homooxacalix [3] arene solubilized C₆₀ into water and the C₆₀ · homooxacalix [3] arene complex acted as an efficient DNA photocleavage reagent. On the other hand, the homooxacalix [3] arene- [60] fullerene complex can be deposited on an anion-coated gold surface as a monolayer (or at least as a monolayer-liked ultra-thin film). This membrane efficiently shows a redox response in cyclic voltammometry and a photoelectrochemical response under visible light irradiation.

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