1,3-Benzenedicarboxylic acid, 5,5'-(5,7-dihydro-1,3,5,7-tetraoxobenzo[1,2-c:4,5-c']dipyrrole-2,6(1H,3H)-diyl)bis-

5,5-(1,3,5,7-tetraoxopyrrolo(3,4-f)isoindole-2,6-diyl)diisophthalic acid