Perylene

Overview
Perylene or perilene is a polycyclic aromatic hydrocarbon with chemical formula 2012 and CAS number, occurring as a brown solid. It or its derivatives may be carcinogenic, and it is considered to be a hazardous pollutant. In cell membrane cytochemistry, perylene is used as a fluorescent lipid probe.

Emission
Perylene displays blue fluorescence. It is used as a blue-emitting dopant material in OLEDs, either pure or substituted. Perylene can be also used as an organic photoconductor. It has an absorption maximum at 434nm, and as with all polycyclic aromatic compounds, low water solubility (1.2 x 10-5 mmol/l). Perylene has a molar extinction coefficient of 38,500 M-1cm-1 at 435.75 nm.

Structure
The perylene molecule consists of two naphthalene molecules connected by a carbon-carbon bond at the 1 and 8 positions on both molecules. All of the carbon atoms in perylene are sp2 hybridized. When drawing the structure of perylene, it is important not to represent the center ring as a fifth benzene ring. By doing so, this would cause two of the carbons to become sp3 hybridized causing part of the molecule to lose its aromaticity, and therefore its ability to fluoresce. The structure of perylene has been extensively studied by X-ray crystallography.