chapter  Chapter 30
7 Pages


WithFranco Cataldo

In general, polyynes are produced with a limited chain length which at most can reach 30 carbon atoms or so, and the chain must be end-capped by end groups. Bulkier (in sterical sense) end-groups ensure higher length and stability to the acetylenic carbon chains. Nonlinear optical properties were found on polyynes and this property can be enhanced by attaching different end groups one electron donor and the other electron acceptor in a push-pull arrangement leading also to hyper-polarizability. Polyynes are important key models to test and applying the surface enhanced Raman spectroscopy. Diphenylpolyynes were synthesized as dinaphthylpolyynes and employed to investigate the charge transfer with metal nanoparticles. Polyynes are thought to be the precursors of fullerenes not only in the carbon arc under helium or in laser ablation experiments. Indeed polyynes and cyanopolyynes were detected by radioastronomy in the circumstellar shell of late-type carbon-rich stars.