title: Near-Infrared Photoelectrochemical Conversion via Photoinduced Charge Separation in Supramolecular Complexes of Anionic Phthalocyanines with Li(+)@C60.
abstract: Two phthalocyanines possessing carboxylate groups ((TBA)4H2Pc·1 and (TBA)4H2Pc·2) form 1:2 supramolecular complexes with lithium cation-encapsulated C60 (Li(+)@C60) [H2Pc·1(4-)/(Li(+)@C60)2 and H2Pc·2(4-)/(Li(+)@C60)2] in a polar mixed solvent. From the UV-vis spectral changes, the binding constants (K) were estimated as ca. 10(12) M(-2). Upon the photoexcitation of constructed supramolecular complexes, photoinduced electron transfer occurred to form the charge-separated (CS) state. The lifetime of the CS state was determined to be 1.2 ms for H2Pc·2(4-)/(Li(+)@C60)2, which is the longest CS lifetime among the porphyrinoid/fullerene supramolecular complexes. H2Pc·1(4-)/(Li(+)@C60)2 also afforded the long-lived CS state of 1.0 ms. The spin state of the long-lived CS states was determined to be a triplet, as indicated by the EPR signal at g = 4. The reorganization energy (λ) and the electronic coupling term were determined to be λ = 1.70 eV, V = 0.15 cm(-1) from the temperature dependence of the rate constant for the charge recombination of the CS state of H2Pc·1(4-)/(Li(+)@C60)2. The energy of the CS state (0.49 eV) is much smaller than the reorganization energy, indicating that the back-electron-transfer process is located in the Marcus normal region. The small electronic coupling term results from the spin-forbidden back electron transfer due to the triplet CS state. Supramolecular complexes of anionic zinc phthalocyanines with Li(+)@C60 were also prepared and investigated. The ZnPc·4(4-)/Li(+)@C60 supramolecular nanoclusters were assembled on the optically transparent electrode (OTE) of nanostructured SnO2 (OTE/SnO2) to construct the dye-sensitized solar cell. The IPCE (incident photon-to-photocurrent efficiency) values of OTE/SnO2/(ZnPc·4(4-)/Li(+)@C60)n were much higher than the sum of the two IPCE values of the individual systems OTE/SnO2/(Li(+)@C60)n and OTE/SnO2/(ZnPc·4(4-))n, covering the near-infrared region.
authors.affiliation: †Department of Material and Life Science, Graduate School of Engineering, Osaka University, and ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kawashima
authors.affiliation: †Department of Material and Life Science, Graduate School of Engineering, Osaka University, and ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Ohkubo
authors.affiliation: ‡Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Edificio Vinalopó, Avda. Universidad s/n, Elche E-03202, Spain.
authors.forename: Vicente Manuel
authors.initials: VM
authors.lastname: Blas-Ferrando
authors.affiliation: §Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Sakai
authors.affiliation: ‡Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Edificio Vinalopó, Avda. Universidad s/n, Elche E-03202, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Font-Sanchis
authors.affiliation: ‡Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Edificio Vinalopó, Avda. Universidad s/n, Elche E-03202, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Ortíz
authors.affiliation: ‡Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Edificio Vinalopó, Avda. Universidad s/n, Elche E-03202, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Fernández-Lázaro
authors.affiliation: §Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Hasobe
authors.affiliation: ‡Área de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Edificio Vinalopó, Avda. Universidad s/n, Elche E-03202, Spain.
authors.forename: Ángela
authors.initials: Á
authors.lastname: Sastre-Santos
authors.affiliation: †Department of Material and Life Science, Graduate School of Engineering, Osaka University, and ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
mesh_terms: D000838:Anions / Q000737:chemistry; D055664:Electrochemical Techniques; D004566:Electrodes; D037741:Fullerenes / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D007259:Infrared Rays; D054833:Isoindoles; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D055668:Photochemical Processes
chemical_list: D000838:Anions; D037741:Fullerenes; D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D008094:Lithium; C069837:fullerene C60; C013647:phthalocyanine