CYCLIC CONJUGATION IN FLUORANTHENE AND ITS BENZO-DERIVATIVES. PART 1. CATACONDENSED SYSTEMS

Continuing our investigations of π -electron properties of fluoranthene-type polycyclic conjugated compounds [Gutman, ?ur?evi?, Balaban, Polycyclic Aromatic Compounds 29 (2009): 3–11], we studied the energy effects of individual rings in fluoranthene and its catacondensed benzo-derivatives (i.e., benzo-annelated fluoranthenes possessing exactly one internal carbon atom). A number of general regularities were observed: (a) the PCP effect (six-membered rings connected by a single bond to the five-membered ring increase in it the intensity of cyclic conjugation), (b), the retro-PCP effect (the five-membered ring increases the intensity of cyclic conjugation in the six-membered rings to which it is connected by a single bond), (c) the linear effect (six-membered rings, linearly annelated to fluoranthene, decrease the cyclic conjugation in the five-membered ring), (d) the magnitude of the PCP effect differs, depending on whether the six-membered ring belongs to the “male” or “female” benzenoid fragment, and (e) the pattern of cyclic conjugationin of isoarithmic benzofluoranthenes is essentially identical.