Reaction of 5,8-Diphenyl-5,8-dihydroanthra[1,9-bc:4,10-b'c']diquinoline or its Endoperoxide with Trifluoroacetic Acid

5, 8-Diphenyl-5, 8-dihydroanthra[1, 9-bc:4, 10-b′c′]diquinoline (ADQ, 3) and its endoperoxide (ADQepo, 4) were photochromic compounds with high heat stability. By heating above 100°C, colorless ADQepo (4) was slowly converted to green ADQ (3) in toluene. Reaction of ADQepo with some protic acid gave ADQ (3) at room temperature. The mechanism of this reaction was proposed based on the measurement of electronic spectrum.