title: Supramolecular Surface Photochemistry: Cascade Energy Transfer between Encapsulated Dyes Aligned on a Clay Nanosheet Surface.
abstract: Three coumarin derivatives (7-propoxy coumarin, coumarin-480, and coumarin-540a, 2, 3, and 4, respectively) having different absorption and emission spectra were encapsulated within a water-soluble organic capsule formed by the two positively charged ammonium-functionalized cavitand octaamine (OAm, 1). Guests 2, 3, and 4 absorb in ultraviolet, violet, and blue regions and emit in violet, blue, and green regions, respectively. Energy transfer between the above three coumarin@(OAm)2 complexes assembled on the surface of a saponite clay nanosheet was investigated by steady-state and time-resolved emission techniques. Judging from their emission and excitation spectra, we concluded that the singlet-singlet energy transfer proceeded from 2 to 3, from 2 to 4, and from 3 to 4 when OAm-encapsulated 2, 3, and 4 were aligned on a clay surface as two-component systems. Under such conditions, the energy transfer efficiencies for the paths 2* to 3, 2* to 4, and 3* to 4 were calculated to be 33, 36, and 50% in two-component systems. When all three coumarins were assembled on the surface and 2 was excited, the energy transfer efficiencies for the paths 2* to 3, 2* to 4, and 3* to 4 were estimated to be 32, 34, and 33%. A comparison of energy transfer efficiencies of the two-component and three-component systems revealed that excitation of 2 leads to emission from 4. Successful merging of supramolecular chemistry and surface chemistry by demonstrating novel multi-step energy transfer in a three-component dye encapsulated system on a clay surface opens up newer opportunities for exploring such systems in an artificial light-harvesting phenomenon.
authors.affiliation: Department of Chemistry, Graduate School of Science, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.|Japan Society for the Promotion of Science (JSPS) , Ichibancho, Chiyoda-ku, Tokyo 102-8471, Japan.
authors.forename: Takamasa
authors.initials: T
authors.lastname: Tsukamoto
authors.affiliation: Department of Chemistry, University of Miami , Coral Gables, Florida 33146-0431, United States.
authors.forename: Elamparuthi
authors.initials: E
authors.lastname: Ramasamy
authors.affiliation: Department of Applied Chemistry, Graduate Course of Urban Environmental Sciences, Tokyo Metropolitan University , 1-1, Minami-ohsawa, Hachiohji-shi, Tokyo 192-0397, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Shimada
authors.affiliation: Department of Applied Chemistry, Graduate Course of Urban Environmental Sciences, Tokyo Metropolitan University , 1-1, Minami-ohsawa, Hachiohji-shi, Tokyo 192-0397, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Takagi
authors.affiliation: Department of Chemistry, University of Miami , Coral Gables, Florida 33146-0431, United States.
authors.forename: V
authors.initials: V
authors.lastname: Ramamurthy
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D003374:Coumarins / Q000737:chemistry*; D004735:Energy Transfer; D004988:Ethers, Cyclic / Q000737:chemistry; D008027:Light; D049329:Nanostructures / Q000737:chemistry*; D055668:Photochemical Processes; D012118:Resorcinols / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D004396:Coloring Agents; D003374:Coumarins; D004988:Ethers, Cyclic; D012118:Resorcinols; C099453:saponite