A combinatorial approach and multinuclear, organo-soluble ruthenium(II) photosensitizers

This thesis is divided into three parts. In the first part, we develop a method of assessing the photosensitization ability of Ru(II) complexes, since Ru(II) complexes of heteroaromatic ligands are photosensitizers of interest in such applications as photovoltaic cells. When samples containing a photosensitizer such as Ru(bpy)32+ (bpy is 2,2'-bipyridine), methyl viologen (MV2+) and the sacrificial reductant triethanolamine (TEOA) are exposed to white light, the blue colour of the methyl viologen cation radical (MV·+) develops by oxidative quenching of the sensitizer's excited state. This occurs even if the samples are not degassed, that is in spite of the known quenching of MV·+ by O2. In degassed media, however, a second pathway of MV+ formation occurs, known to involve the reduction of MV2+ by the oxidized and deprotonated form of TEOA (H-1TEOA) that arises from its function as a sacrificial reductant.;In the third part, we explore new catechol-bearing complexes of Ru(II) and the means by which they might be joined into linear arrays in a pseudo-combinatorial approach to the discovery of new, more efficient photosensitizers and photovoltaic materials. A new tridentate ligand with a peripheral catechol grouping in protected form, 4-(3,4-methylenedioxyphenyl)-2,6-dipyrazinylpyridine, was prepared in good yield in a one-pot reaction. Its homoleptic and heteroleptic Ru(II) complexes were prepared in good yields, and tested as photosensitizers against previously known analogues. The photosensitization abilities were explainable in terms of mechanism and driving force. (Abstract shortened by UMI.);In the second part, we devise a combinatorial protocol for the identification of promising Ru(II) sensitizers that uses the screening method developed in the first part. The bulk preparation of Ru(II) sensitizers is tedious, time-consuming and expensive. The identification of new, promising photosensitizers would therefore greatly benefit from any time- and cost-saving protocol, if absolute purity is not required for assessment. This part details a protocol for the fairly rapid preparation, in parallel and on a small scale, of organosoluble Ru(II) complexes in a state ready for screening for photosensitization ability.