Molecules, perethynylated

This article summarizes efforts undertaken towards the synthesis of the cyclo[ ]carbons, the first molecular carbon allotropes for which a rational preparative access has been worked out. Subsequently, a diversity of perethynylated molecules will be reviewed together, they compose a large molecular construction kit for acetylenic molecular scaffolding in one, two and three dimensions. Finally, progress in the construction and properties of oligomers and polymers with a poly(triacetylene) backbone, the third linearly conjugated, non-aromatic all-carbon backbone, will be reviewed. 

Tetraethynylethenes, Fully Cross-Conjugated n-Electron Chromophores, and Other Perethynylated Molecules... 

In Section 13-4, it will be shown that tetraethynylethenes are potential monomers for the construction of all-carbon networks [1]. Other perethynylated compounds have been reported, which could also serve as building blocks for infinite two- and three-dimensional carbon nets [46]. They all represent fascinating small molecules of substantial structural and electronic interest [1, 2, 47]. 

Scheme 13-9 Synthesis of perethynylated molecules and transition metal complexes as potential precursors to carbon networks.

Radialenes (49) are a homologous series of all-eA o-methylenecycloalkanes of molecular formula C H (Fig. 13-3) [60], Upon insertion of butadiynyl moieties into the cyclic framework between each pair of vicinal ejto-methylene units, the carbon-rich expanded radialenes 50 (C3 H ) are obtained. Starting from suitable protected tetraethynylethenes, the perethynylated expanded radialenes 51-53 were prepared via 54, as shown in Scheme 13-11 [41], They possess large carbon cores with silyl-protected peripheral valences and can be viewed as C40 + 8 (/Pr)3Si (51), Cjo + 10 (iPr)3Si (52), and C , + 12 (/Pr)3Si (53). The diameters of these large carbon-rich molecules are in the nanometer range with values of = 17 A (for 51), 19 A (for 52), and 22 A (for 53). 

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