Abstract
Hexaarylbenzenes (HABs) are valuable precursors for the bottom-up synthesis of (nano-)graphene
structures. In this work the synthesis of several bis-pyrimidine substituted HABs
furnished with tert-butyl groups at different sites of the four pendant phenyl rings is reported. The
synthetic procedure is based on modular [4 + 2]-Diels–Alder cycloaddition reactions
followed by decarbonylation. Analysis of the solid-state structures revealed that
the newly synthesized HABs feature a propeller-like arrangement of the six arylic
substituents around the benzene core. Here, the tilt of the aryl rings with respect
to the central ring strongly depends on the intermolecular interactions between the
HABs and co-crystallized solvent molecules. Interestingly, by evading the closest
proximity of the central ring using an alkyne spacer, the distant pyrimidine ring
is oriented in the coplanar geometry with regard to the benzene core, giving rise
to a completely different UV-absorption profile.
Key words
carbon materials - cycloadditions - Diels–Alder reactions - doping - ligand design
- N-heterocycles
