Highly Polarized Benzo[k]fluoranthene Imide Derivatives: Large Solvatofluorochromism, Dual Fluorescence and Aggregation Induced Emission Associated with Excited-State Intramolecular Charge Transfer.

The highly conjugated imides, 9-diphenyl-aminobenzo[k]fluoranthene imide and N-phenylcarbazo[2,3-k]fluoranthene imide, were produced by Buchwald-Hartwig reaction of N-octyl-9,10-dibromobenzo[k]fluoranthene imide with diphenylamine. In a similar manner, reaction of the N-ethylhexyl-9,10-dibromo derivative with carbazole leads to formation of 9-(N-carbazoyl)benzo[k]fluoranthene imide. All the benzo[k]fluoranthene imide (BFI) derivatives in solution show remarkable solvatofluorochromism. Diphenylamino and 9-(N-carbazoyl) derivatives, having twisted structures, exhibit fluorescence bands at short wavelengths in highly polar solvents, and they emit dual fluorescence in acetone. Moreover, the 9-(N-carbazoyl) derivative displays aggregation-induced emission in highly aqueous acetone solutions. The results of density functional theory calculations demonstrate that a considerable spatial separation exists between the HOMO and LUMO coefficients of the N-arylamine substituted BFIs. The results indicate that the ground-to-excited state transitions of these compounds have intramolecular charge transfer character.

Is death-feigning adaptive? Heritable variation in fitness difference of death-feigning behaviour.

The adaptation of death-feigning (thanatosis), a subject that has been overlooked in evolutionary biology, was inferred in a model prey-and-predator system. We studied phenotypic variation among individuals, fitness differences, and the inheritance of death-feigning behaviour in the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Two-way artificial selections for the duration of death-feigning, over 10 generations, showed a clear direct response in the trait and a correlated response in the frequency of death-feigning, thus indicating variation and inheritance of death-feigning behaviour. A comparison of the two selected strains with divergent frequencies of death-feigning showed a significant difference in the fitness for survival when a model predator, a female Adanson jumper spider, Hasarius adansoni Audouin (Araneomophae: Salticidae), was presented to the beetles. The frequency of predation was lower among beetles from strains selected for long-duration than among those for short-duration death-feigning. The results indicate the possibility of the evolution of death-feigning under natural selection.