Delayed Fluorescence by Triplet-Triplet Annihilation from Columnar Liquid Crystal Films.

Delayed fluorescence (DF) by triplet-triplet annihilation (TTA) is observed in solutions of a benzoperylene-imidoester mesogen that shows a hexagonal columnar mesophase at room temperature in the neat state. A similar benzoperylene-imide with a slightly smaller HOMO-LUMO gap, that also is hexagonal columnar liquid crystalline at room temperature, does not show DF in solution, and mixtures of the two mesogens show no DF in solution either, because of collisional quenching of the excited triplet states on the imidoester by the imide. In contrast, DF by TTA from the imide but not from the imidoester is observed in condensed films of such mixtures, even though neat films of either single material are not displaying DF.

Columnar Liquid-Crystalline Dibenzopentacenodithiophenes by Photocyclization.

The twofold glyoxylic Perkin reaction of perylene-3,9-diglyoxylic acid with thiophene-diacetic acid followed by oxidative photocylization and reaction with α-branched primary alkylamines yields columnar liquid-crystalline diimides with two sulfur atoms in the condensed arene system. A broad temperature range of the hexagonal columnar mesophase is induced by racemic doubly branched alkyl chains. The HOMO and LUMO energy levels of these thiophene-derived diimides qualify them as electron donors with respect to perylene diimides.