Polyethynylated cyclic π-systems: scaffoldings for novel two and three-dimensional carbon networks

All-carbon materials with novel topologies are of interest in regard to their materials properties. These novel structures include graphite-like two-dimensional networks as well as fullerene-like three-dimensional cages. This article reviews recent developments in the synthesis of scaffolds for novel forms of carbon made of a core π-system carrying alkyne appendages, such as hexaethynylbenzene and its derivatives, pentaethynylcyclopentadienyl metal complexes, and tetraethynylcyclobutadiene metal complexes. Also included are the syntheses and properties of macrocyclic π-systems derived of these units which represent important substructures for the infinite lattices of novel carbon allotropes.