Lalith P. Samankumara, M. Zeller, J. Krause
Mar 31, 2010
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Organic & biomolecular chemistry
Abstract
The refined syntheses, modification, and first X-ray structural characterization of meso-tetraarylporphyrin-derived beta-tetraolbacteriochlorins are described. These investigations assign the relative stereochemistry of their two isomers (both cis-vic-diol pairs on the same or opposite sides of the porphyrin plane), an assignment that could not be provided by NMR, UV-vis or fluorescence spectroscopy, or mass spectrometry. Moreover, the first crystal structures of a 2-hydroxychlorin and a 2,3-dihydroxychlorin, as its dimethylether, are reported. Dihydroxylation and diimide reduction of the dimethoxychlorin result in the formation of stable mixed-functionality bacteriochlorins. The photophysical properties (UV-vis absorption and fluorescence emission) of all chromophores are contrasted against each other, delineating the electronic effects of diol substitution and conformational modulation. Lastly, the acid-induced dehydration/demethoxylation of the tetraol-, dioldimethoxy-, and tetramethoxybacteriochlorins to provide chlorins is delineated.