| Abstract: | Summary. (A) The origin of exciton interaction and examples of its application to organic stereochemistry are presented. (B) N,N -Carbonyl-bridged dipyrrinones constitute a new class of highly fluorescent chromophores suitable for investigations of stereochemistry and absolute configuration. N,N-Carbonylxanthobilirubic acid esters are strongly fluorescent, with a fluorescence quantum yield ( F)  0.8, but produce only weak exciton CD from the trans-1,2-cyclohexanediol template. The ester of an analog with benzoic acid replacing propionic, N,N-carbonyl-8-(4-carboxyphenyl)-3-ethyl-2,7,9-trimethyl-(10H)-dipyrrin-1-one, exhibits strong fluorescence (F=0.68,  em=493 nm, ex=422nm in CHCl3) and UV-Vis absorption ( 21000 at 424nm) in organic solvents. Its diester with (1S,2S)-cyclohexanediol is fluorescent and exhibits exciton circular dichroism ( =+15dm3·mol–1·cm–1, =432nm; =–4dm3·mol–1cm–1, =380nm) that correlates with the Exciton Chirality Rule. |
