摘要:
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: DELTA-epsilon-408max-122.5, DELTA-epsilon-360max+95 (1 in CH2Cl2) and DELTA-epsilon-318max-88.5, DELTA-epsilon-292max+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[p-(dimethylamino)benzoate ester].