title: Photoinduced electron transfer and excitation energy transfer in directly linked zinc porphyrin/zinc phthalocyanine composite.
abstract: Photoinduced electron transfer (ET) and excitation energy transfer (ENT) reactions in monomer and slipped-cofacial dimer systems of a directly linked Zn porphyrin (Por)-Zn phthalocyanine (Pc) heterodyad, ZnPc-ZnPor, were investigated by means of the picosecond and femtosecond transient absorption spectroscopies. In the dimer dyad system of two heterodyads connected through the coordination bond between two imidazolyl-substituted ZnPor bearing ZnPc, ZnPc-ZnPor(D), the rapid ENT from the ZnPor to ZnPc in the subpicosecond time region was followed by photoinduced charge separation (CS) and charge recombination (CR) with time constants of 47 and 510 ps, respectively. On the other hand in the monomer dyad system, no clear charge-separated state was observed although the CS with a time constant of 200 ps and CR with < or =70 ps were estimated. These results indicated that the dimer slipped-cofacial arrangement of pair porphyrins is advantageous for the effective production of the CS state. This advantage was discussed from the viewpoint of a decrease in the reorganization energy of the dimer relative to that of the monomer system. In addition, the electrochemical measurements indicated that the strong interaction between ZnPc and ZnPor moieties also contributed to the fast CS process despite the marginal driving force for the CS process. The dimer dyad of ZnPc-ZnPor provides full advantages in efficiencies of the light harvesting and the CS state production.
authors.affiliation: Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. f-ito@cstf.kyushu-u.ac.jp
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Ito
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Ishibashi
authors.forename: Sazzadur Rahman
authors.initials: SR
authors.lastname: Khan
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyasaka
authors.forename: Kazuya
authors.initials: K
authors.lastname: Kameyama
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Morisue
authors.forename: Akiharu
authors.initials: A
authors.lastname: Satake
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ogawa
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kobuke