Exciton Coupling from Dipyrrinone Chromophores

Article abstract of DOI:10.1021/jo00021a013

2,3,7,8-Tetramethyl-(10H)-dipyrrin-1-one-9-carboxylic acid and p-(dimethylamino)benzoic acid are reacted separately with (1R,2R)-cyclohexanediol to form the corresponding diesters (1 and 3, respectively).These diesters exhibit intense bisignate circular dichroism (CD) spectra characteristic of exciton coupling and show a negative exciton chirality: Δε^max₄₀₈ -122.5, Δε^max₃₆₀ +95 (1 in CH2Cl2) and Δε^max₃₁₈ -88.5 , Δε^max₂₉₂ +41.5 (3 in CH2Cl2).In (CH3)2SO solvent the Cotton effect signs become inverted for the bis(dipyrrinone ester) but remain unchanged for the bis.