Intramolecular Electron Transfer Reactions Observed for Dawson-Type Polyoxometalates Covalently Linked to Porphyrin Residues

被引:102
作者
Harriman, Anthony [1 ]
Elliott, Kristopher J. [1 ]
Alamiry, Mohammed A. H. [1 ]
Le Pleux, Loic [2 ]
Severac, Marjorie [2 ]
Pellegrin, Yann [2 ]
Blart, Errol [2 ]
Fosse, Celine [3 ]
Cannizzo, Caroline [4 ]
Mayer, Cedric R. [5 ]
Odobel, Fabrice [2 ]
机构
[1] Univ Newcastle, Mol Photon Lab, Sch Chem, Bedson Bldg, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[2] Univ Nantes, CNRS, UMR 6230, F-44322 Nantes 3, France
[3] Ecole Natl Super Chim Paris, Lab Spectrometrie Masse, F-75231 Paris 05, France
[4] Ecole Natl Super Chim Paris, Serv Spectrometrie Masse, F-75231 Paris 05, France
[5] Univ Versailles St Quentin, CNRS, Inst Lavoisier Versailles, UMR 8180, F-78035 Versailles, France
关键词
OPTICAL-PROPERTIES; FLASH-PHOTOLYSIS; HYBRID FILMS; METALLOPORPHYRINS; CATALYSIS; WATER; ZINC; COMPLEXES; OXIDATION; REDUCTION;
D O I
10.1021/jp900643m
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Three photoactive, multicomponent supermolecules have been synthesized and characterized whereby a porphyrin unit is covalently linked to a Dawson-type heteropolyphosphotungstate (POM). The connection has been made via a Huisgen reaction, which gives good yields in all cases, and modified to provide linkages that vary in their degree of internal flexibility. Fluorescence from the porphyrin unit is quenched by the appended POM, for which the efficiency increases with increasing flexibility of the linker. Except for the most rigid connection, fluorescence decay profiles are nonexponential and are interpreted in terms of multiple families of conformers that differ in their ability to undergo light-induced electron transfer. The distribution of ground-state conformers was examined by high-pressure emission spectroscopy. Cyclic voltammetry and spectro-electrochemical studies provide quantitative data for the thermodynamic driving forces and spectral data for the redox products. In all cases, the first-excited singlet state resident on the porphyrin is capable of transferring an electron to the POM. The rate of electron transfer is very slow for the corresponding triplet state of the porphyrin. Photolysis of the porphyrin in the presence of triethanolamine, present as a sacrificial electron donor, leads to formation of the porphyrin pi-radical anion. This latter species is able to reduce the POM, but the rate of reaction is remarkably slow. Here, bimolecular electron transfer competes effectively with the intramolecular route, confirming that the triazole linker is a poor conduit for electrons. It was not possible, under these conditions, to load the POM with more than a single electron. The one-electron reduced form of the POM transfers an electron to the singlet-excited-state of the porphyrin so as to form a relatively long-lived charge-shift state.
引用
收藏
页码:5834 / 5842
页数:9
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