title: A new approach for the photosynthetic antenna-reaction center complex with a model organized around an s-triazine linker.
abstract: Two new artificial mimics of the photosynthetic antenna-reaction center complex have been designed and synthesized (BDP-H2 P-C60 and BDP-ZnP-C60). The resulting electron-donor/acceptor conjugates contain a porphyrin (either in its free-base form (H2P) or as Zn-metalated complex (ZnP)), a boron dipyrrin (BDP), and a fulleropyrrolidine possessing, as substituent of the pyrrolidine nitrogen, an ethylene glycol chain terminating in an amino group C60-X-NH2 (X=spacer). In both cases, the three different components were connected by s-triazine through stepwise substitution reactions of cyanuric chloride. In addition to the facile synthesis, the star-type arrangement of the three photo- and redox-active components around the central s-triazine unit permits direct interaction between one another, in contrast to reported examples in which the three components are arranged in a linear fashion. The energy- and electron-transfer properties of the resulting electron-donor/acceptor conjugates were investigated by using UV/Vis absorption and emission spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. Comparison of the absorption spectra and cyclic voltammograms of BDP-H2P-C60 and BDP-ZnP-C60 with those of BDP-H2P, BDP-ZnP and BDP-C60, which were used as references, showed that the spectroscopic and electrochemical properties of the individual constituents are basically retained, although some appreciable shifts in terms of absorption indicate some interactions in the ground state. Fluorescence lifetime measurements and transient absorption experiments helped to elucidate the antenna function of BDP, which upon selective excitation undergoes a rapid and efficient energy transfer from BDP to H2P or ZnP. This is then followed by an electron transfer to C60, yielding the formation of the singlet charge-separated states, namely BDP-H2(·+) -C60(·-) and BDP-ZnP(·+)-C60(·-). As such, the sequence of energy transfer and electron transfer in the present models mimics the events of natural photosynthesis.
authors.affiliation: Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Egerlandstr. 3, 91058 Erlangen (Germany).
authors.forename: Susanne
authors.initials: S
authors.lastname: Kuhri
authors.forename: Georgios
authors.initials: G
authors.lastname: Charalambidis
authors.forename: Panagiotis A
authors.initials: PA
authors.lastname: Angaridis
authors.forename: Theodore
authors.initials: T
authors.lastname: Lazarides
authors.forename: Georgia
authors.initials: G
authors.lastname: Pagona
authors.forename: Nikos
authors.initials: N
authors.lastname: Tagmatarchis
authors.forename: Athanassios G
authors.initials: AG
authors.lastname: Coutsolelos
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
mesh_terms: D001895:Boron / Q000737:chemistry; D055664:Electrochemical Techniques; D004579:Electron Transport; D019855:Ethylene Glycol / Q000737:chemistry; D037741:Fullerenes / Q000737:chemistry; D008665:Metalloporphyrins / Q000737:chemistry; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D011759:Pyrrolidines / Q000737:chemistry; D014227:Triazines / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
chemical_list: D037741:Fullerenes; D008665:Metalloporphyrins; D045322:Photosynthetic Reaction Center Complex Proteins; D011166:Porphyrins; D011759:Pyrrolidines; D014227:Triazines; D019855:Ethylene Glycol; D015032:Zinc; C032519:pyrrolidine; D001895:Boron
keywords: cyclic voltammetry; electron transfer; energy transfer; photosynthesis; synthetic methods