Parallel synthesis and rapid photochemical screening of organosoluble Ru(II) photosensitizers

Ru(II) complexes of heteroaromatic ligands are photosensitizers of interest in such applications as photovoltaic cells. Their bulk preparation is tedious, time-consuming, and expensive. Their assessments, by measurement of the individual excited-state lifetimes, is incomplete and requires specialized equipment and expertise, as well as time. 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 paper 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. The protocol was tested with a small set of bidentate ligands, generating 20 possible complexes, many of which are known. The protocol was found to produce predominantly the desired species in all cases except those with three different ligands. The batch screening results for the remaining 16 complexes were entirely consistent with those obtained with pure samples of the most promising materials prepared in bulk and were consistent with known photophysical properties.