Efficient Photoinduced Electron Transfer in a Porphyrin Tripod-Fullerene Supramolecular Complex via π-π Interactions in Nonpolar Media Atsuro Takai, † Mohammed Chkounda, ‡ Antoine Eggenspiller, ‡ Claude P. Gros, ‡ Mohammed Lachkar, § Jean-Michel Barbe,* ,‡ and Shunichi Fukuzumi* ,†,| Department of Material and Life Science, DiVision of AdVanced Science and Biotechnology, Graduate School of Engineering, Osaka UniVersity, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan, ICMUB, UMR CNRS 5260, UniVersite ´ de Bourgogne, 9 AVenue Alain SaVary, BP 47870, 21078 Dijon Cedex, France, UniVersite ´ Sidi Mohamed Ben Abdellah, Faculte ´ des Sciences Dhar El Mahraz, Laboratoire d’Inge ´nierie des Mate ´riaux Organome ´talliques et Mole ´culaires “L.I.M.O.M.”, De ´partement de Chimie, B.P. 1796 (Atlas), 30000 Fe `s, Maroc, Department of Bioinspired Science, Ewha Womans UniVersity, Seoul 120-750, Korea Received January 9, 2010; E-mail: fukuzumi@chem.eng.osaka-u.ac.jp; Jean-Michel.Barbe@u-bourgogne.fr Abstract: A novel porphyrin tripod (TPZn 3 ) was synthesized via “click chemistry”. Three porphyrin moieties of TPZn 3 are geometrically close and linked by a flexible linker. The electron-transfer oxidation of TPZn 3 results in intramolecular π-dimer formation between porphyrin moieties as indicated by electrochemical, vis-NIR, and ESR measurements. The cyclic voltammogram of TPZn 3 exhibited stepwise one-electron oxidation processes of three porphyrin moieties in the range from 0.58 to 0.73 V (vs SCE in CH 2 Cl 2 ). When TPZn 3 was oxidized by tris(2,2′-bipyridyl)-ruthenium(III) ([Ru(bpy) 3 ] 3+ ), the oxidized species (TPZn 3 ) n+ (0 < n e 3) exhibited a charge resonance band in the NIR region due to the π-dimer formation between porphyrin moieties. A supramolecular electron donor-acceptor system was also constructed using TPZn 3 . The flexible conformation of TPZn 3 makes it possible to capture a fullerene derivative containing a pyridine moiety (PyC 60 ) inside the cavity by π-π interactions as well as the coordination bond between Zn 2+ and the pyridine moiety. The formation of a 1:1 supramolecular complex of TPZn 3 with PyC 60 (TPZn 3 -PyC 60 ) was indicated in the UV-vis and 1 H NMR spectra in nonpolar solvents. The association constant of TPZn 3 with PyC 60 (1.1 × 10 5 M -1 in toluene) is much larger as compared with those of the corresponding monomer (MPZn) and dimer porphyrin (DPZn 2 ). The dynamics of photoinduced electron transfer from the singlet excited state of TPZn 3 to PyC 60 was examined by laser flash photolysis measurements. The efficient intracomplex photoinduced electron transfer in TPZn 3 -PyC 60 occurred in nonpolar solvents, resulting from the π-π interactions between the porphyrin and fullerene moieties, together with intramolecular π-bond formation between the porphyrin radical cation and the neutral porphyrin in TPZn 3 •+ . Introduction In the initial photosynthetic process, the light energy collected by chlorophyll assemblies, light-harvesting antenna, is funneled into photosynthetic reaction center. 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