Stabilization of reactive sp carbon chains

We describe a novel strategy for stabilizing the long-elusive, condensed-state materials consisting of sp carbon chains. High-level ab initio calculations indicate that covalent attachment of such carbon chains to gold thiolate clusters stabilizes the cumulenic (double bonded [dbnd]C[dbnd]C[dbnd]C[dbnd]) form, whereas a non-covalent interaction stabilizes the polyynic (alternating single/triple bonded –C[tbnd]C–C[tbnd]C-) form. The Raman-active CC stretching mode is a sensitive probe of these bonding differences. This mode occurs at the same frequencies as that of isolated polyynes in non-covalent complexes, but it appears at lower wavenumbers in the covalent complexes. The current work provides a new direction for the synthesis and stabilization of materials containing sp carbon chains.