Photochemical reaction of lucigenin : electron-transfer reduction of 10,10′-dimethyl-9,9′-biacridinediium by counter anions, followed by photocyclization
Lucigenin (1) is a charge-transfer complex between 10,10′-dimethyl-9,9′-biacridinediium (DMBA2+) and two nitrate anions. When the complex (1) was irradiated in the charge-transfer absorption band (>510 nm) in deaerated solutions, DMBA2+ was converted into the reduced form, 10,10′-dimethyl-9,9′-biacridylidene (2). On the other hand, irradiation of (1) with visible light (>420 nm) gave a red product
The photolysis of 10,10′-disubstituted 9,9′(10H,10′H)-biacridinylidenes afforded the corresponding 7,16-dihydrobenzo[1,2,3-kl:6,5,4-k′l′]diacridines. The formation of photocyclized dihydrophenanthrene-type intermediates was confirmed spectroscopically.