The photochemistry of 6-phenanthridinecarbonitrile I. Product analysis [1]

Article abstract of DOI:10.1002/jhet.5570370212

When 6-phenanthridinecarbonitrile (3) is irradiated at 2537 A in neutral 9:1 2-propanol/water, three major products are formed. These are dimethyl-(6-phenanthridinyl)methanol (4), phenanthridine (5) and 6,6'- biphenanthridine (6). When benzophenone is present in the reaction mixture, diphenyl-(6-phenanthridinyl)methanol is also formed. 6-Phenanthridinyl radical which is common to the formation of all these products, is formed by a monophotonic process involving hydrogen atom abstraction from an alcohol molecule by an excited state of 3. Unlike what is generally found with other nitrogen-heterocycles, the photochemistry of 3 appears to involve only a π,π* singlet state. The fluorescence of 3 is quenched with the triplet quencher cis/trans-piperylene as a function of the concentration of the diene without the accompaniment of an exciplex emission.