title: Remarkably efficient photocurrent generation based on a [60]fullerene-triosmium cluster/Zn-porphyrin/boron-dipyrrin triad SAM.
abstract: A new artificial photosynthetic triad array, a [60]fullerene-triosmium cluster/zinc-porphyrin/boron-dipyrrin complex (1, Os(3)C(60)/ZnP/Bodipy), has been prepared by decarbonylation of Os(3)(CO)(8)(CN(CH(2))(3)Si(OEt)(3))(mu(3)-eta(2):eta(2):eta(2)-C(60)) (6) with Me(3)NO/MeCN and subsequent reaction with the isocyanide ligand CNZnP/Bodipy (5) containing zinc porphyrin (ZnP) and boron dipyrrin (Bodipy) moieties. Triad 1 has been characterized by various spectroscopic methods (MS, NMR, IR, UV/Vis, photoluminescence, and transient absorption spectroscopy). The electrochemical properties of 1 in chlorobenzene (CB) have been examined by cyclic voltammetry; the general feature of the cyclic voltammogram of 1 is nine reversible one-electron redox couples, that is, the sum of those of 5 and 6. DFT has been applied to study the molecular and electronic structures of 1. On the basis of fluorescence-lifetime measurements and transient absorption spectroscopic data, 1 undergoes an efficient energy transfer from Bodipy to ZnP and a fast electron transfer from ZnP to C(60); the detailed kinetics involved in both events have been elucidated. The SAM of triad 1 (1/ITO; ITO=indium-tin oxide) has been prepared by immersion of an ITO electrode in a CB solution of 1 and diazabicyclo-octane (2:1 equiv), and characterized by UV/Vis absorption spectroscopy, water contact angle, X-ray photoelectron spectroscopy, and cyclic voltammetry. The photoelectrochemical properties of 1/ITO have been investigated by a standard three-electrode system in the presence of an ascorbic acid sacrificial electron donor. The quantum yield of the photoelectrochemical cell has been estimated to be 29 % based on the number of photons absorbed by the chromophores. Our triad 1 is unique when compared to previously reported photoinduced electron-transfer arrays, in that C(60) is linked by pi bonding with little perturbation of the C(60) electron delocalization.
authors.affiliation: Department of Chemistry and School of Molecular Science, Korea Advanced Institute of Science and Technology, Daejeon, 305-701 Korea.
authors.forename: Chang Yeon
authors.initials: CY
authors.lastname: Lee
authors.forename: Jae Kwon
authors.initials: JK
authors.lastname: Jang
authors.forename: Chul Hoon
authors.initials: CH
authors.lastname: Kim
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Jung
authors.forename: Bo Keun
authors.initials: BK
authors.lastname: Park
authors.forename: Jihee
authors.initials: J
authors.lastname: Park
authors.forename: Wonyong
authors.initials: W
authors.lastname: Choi
authors.forename: Young-Kyu
authors.initials: YK
authors.lastname: Han
authors.forename: Taiha
authors.initials: T
authors.lastname: Joo
authors.forename: Joon T
authors.initials: JT
authors.lastname: Park