First identification of benzo[cd]phenanthro[1,2,3-lm]perylene by high-pressure liquid chromatography with ultraviolet-visible spectroscopy and mass spectrometry

Benzo[cd]phenanthro[1,2,3-lm]perylene has been identified as a product of supercritical 1-methylnaphthalene pyrolysis from an experiment performed at 585 °C, 110 atm, and 140 s in a supercritical fluid flow reactor. The identification of benzo[cd]phenanthro[1,2,3-lm]perylene is based on the product's mass spectrum, HPLC elution time, and UV absorbance spectrum. The mass spectrum of the identified 1-methylnaphthalene pyrolysis product, called component I here, reveals a molecular weight of 426, corresponding to a C34H18 polycyclic aromatic hydrocarbon (PAH). The extremely long HPLC elution time, 20–48 min longer than those of the four other C34H18 PAH components in this product mixture, indicates that component I has a planar structure with a high length-to-breadth ratio. Annellation theory is used to interpret and compare the UV spectrum of component I with those of the C30H16 benzo[cd]naphtho[1,2,3-lm]perylene and the C36H18 teropyrene, structures with one ring less and one ring more, respectively, than that of component I. This analysis of component I's UV spectrum, in conjunction with its mass spectrum and HPLC elution behavior, all lead to the identification of component I as the nine-ring PAH benzo[cd]phenanthro[1,2,3-lm] perylene, a molecule whose existence has never before been documented.