Fluorescent J-type aggregates and thermotropic columnar mesophases of perylene bisimide dyes

A series of perylene tetracarboxylic acid bisimides 3a-e bearing 3,4,5-trid odecyloxyphenyl substituents on the imide N atoms and zero, two, or four ph enoxy-type substituents in the bay positions of the perylene core were synt hesized. From investigations of their spectroscopic properties and aggregat ion behavior in low-polarity solvents by absorption and fluorescence optica l spectroscopy, not only were these compounds found to form fluorescent J-t ype aggregates, but also binding constants for aggregation could be derived which reflect the number and steric demand of the phenoxy substituents for bisimides 3a-d. In the pristine state, 3a-d form thermotropic hexagonal co lumnar mesophases which exist over a broad temperature range from below -30 degreesC to over 300 degreesC. For the tetraphenoxy-substituted compound 3 e, however, a layered crystalline structure was found. This difference in b ehavior can be explained by the concept of microphase segregation of the ar omatic cores of the molecules and the alkyl chains at the periphery. The hi gh stability and bright fluorescence of the mesophase of several of the com pounds make them promising for applications as polarizers or components in (opto)electronic devices.