Preparation and Spectroscopic Characterization of Cyclopenta[l,2-a: 3,4,5-b'c']dicoronene

Dicoronylene Isomers, UV/VIS Absorption Spectra, Fluorescence Spectra The non-alternant hydrocarbon cyclopenta[l,2-a:3,4,5-b'c']dicoronene (3) has been pre­ pared by aluminium chloride catalyzed dimerization o f coronene (1). The UV/VIS absorption spectrum, fluorescence spectrum and fluorescence quantum yield o f 3 is reported and com ­ pared with that o f the alternant isomer benzo[l,2,3-bc:4,5,6-b'c']dicoronene (2). Relationships observed in the UV/VIS absorption spectra o f alternant and non-alternant polycyclic aromatic hydrocarbons and preliminary theoretical investigations (PMO calculations) on two model systems (C, E) are also reported.