Fluorescent columnar liquid crystalline 3,4,9,10-tetra-(n-alkoxycarbonyl)-perylenes

The title compounds were recently demonstrated to be useful as luminescent electron transport materials in organic light emitting diodes. Here, we pre sent studies of the fluorescence of the homologues with chain lengths betwe en 2 and 10 carbon atoms. Dilute solutions of the investigated compounds sh ow absorption in the range between 410 and 490 nm and fluorescence between 475 and 555 nm. However, the columnar phase of the pure compounds exhibits fluorescence at considerably larger wavelength (550-650 nn) and gives large r fluorescence lifetimes. This behaviour can be explained by the formation of excimers in the mesophase. The phase transitions to the liquid crystal s tate are associated with a distinct change of the fluorescence intensity.