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

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