- Varying the electronic structure of surface-bound ruthenium(II) polypyridyl complexes
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In the design of light-harvesting chromophores for use in dye-sensitized photoelectrosynthesis cells (DSPECs), surface binding to metal oxides in aqueous solutions is often inhibited by synthetic difficulties. We report here a systematic synthesis approach for preparing a family of Ru(II) polypyridyl complexes of the type [Ru(4,4′-R2-bpy)2(4,4′-(PO3H2)2-bpy)]2+ (4,4′(PO3H2)2-bpy = [2,2′-bipyridine]-4,4′-diylbis(phosphonic acid); 4,4′-R2-bpy = 4,4′-R2-2,2′-bipyridine; and R = OCH3, CH3, H, or Br). In this series, the nature of the 4,4′-R2-bpy ligand is modified through the incorporation of electron-donating (R = OCH3 or CH3) or electron-withdrawing (R = Br) functionalities to tune redox potentials and excited-state energies. Electrochemical measurements show that the ground-state potentials, E′(Ru3+/2+), vary from 1.08 to 1.45 V (vs NHE) when the complexes are immobilized on TiO2 electrodes in aqueous HClO4 (0.1 M) as a result of increased Ru dπ-π back-bonding caused by the lowering of the π orbitals on the 4,4′-R2-bpy ligand. The same ligand variations cause a negligible shift in the metal-to-ligand charge-transfer absorption energies. Emission energies decrease from max = 644 to 708 nm across the series. Excited-state redox potentials are derived from single-mode Franck-Condon analyses of room-temperature emission spectra and are discussed in the context of DSPEC applications.
- Ashford, Dennis L.,Brennaman, M. Kyle,Brown, Robert J.,Keinan, Shahar,Concepcion, Javier J.,Papanikolas, John M.,Templeton, Joseph L.,Meyer, Thomas J.
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p. 460 - 469
(2015/01/30)
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- Phosphonic acid anchored ruthenium complexes for ZnO-based dye-sensitized solar cells
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We report on the development of ruthenium dyes for the application in flexible ZnO based dye-sensitized solar cells. The ZnO based solar cells were prepared by electrodeposition using eosin Y as a structure-directing agent. The newly synthesized ruthenium dyes differed in the complexity of the extended π-donor-system and in their anchor moieties. As alternatives to carboxylic acids as anchor groups, dyes carrying phosphonic acids were studied. Comparison of the dyes contrary to what could be expected showed that the phosphonic acid anchored dyes were not superior to the carboxylic anchored dyes. A surprising second effect was that the dyes with the least sophisticated ligands performed best. Exploring possible reasons we established a simple model that allows pre-evaluation of the applicability of the dyes before testing them in real solar cells.
- Neuthe, Katja,Bittner, Florian,Stiemke, Frank,Ziem, Benjamin,Du, Juan,Zellner, Monika,Wark, Michael,Schubert, Thomas,Haag, Rainer
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- Facile and efficient syntheses of 2,2'-bipyridine-based bis(phosphonic) acids
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The synthesis and characterization of new 2,2'-bipyridine ligands bearing two phosphonic acid groups either on the (4,4'), (5,5') or (6,6') positions are described.
- Penicaud, Virginie,Odobel, Fabrice,Bujoli, Bruno
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p. 3689 - 3692
(2007/10/03)
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