Abstract
[n]Annulenes (n ≥12) condensed with
2-4 aromatic ring systems (benzenes, naphthalenes, anthracenes,
phenanthrenes, chrysenes, pyrenes) can be prepared by cyclocondensation
reactions or ring transformations. Due to the local arene aromaticity,
the molecules can be regarded as aromatic islands, which are connected by
olefinic bridges. The compounds are non-planar, but the majority of
the systems shows a fast inversion of the central macrocyclic ring,
so that the molecules appear on average as large planar discs, which
consist of extended π systems. The aggregation tendency
(π stacking) of the compounds can be strengthened by the
attachment of flexible saturated chains on the periphery. The discs
represent then mesogens for columnar (or nematic) discotic LC phases.
Because of the stilbenoid character, the compounds show a variety
of interesting photophysical and photochemical properties. They
can be applied in photoconductive liquid crystalline phases Colh and
in radiation-induced imaging techniques.
Key words
annulenes - condensation - ring closure - aggregation - photochemistry
