Synthesis, structure and thermal properties of copper and silver polyynides and acetylides

Abstract

Polyynes or oligoynes having general formula H-(C≡C) n-H with n = 1,2,3,4,..., are a class of molecules that has become easily accessible in recent years due to new synthetic approaches. These molecules form copper and silver salts, which have been called, respectively, Cu-polyynides and Ag-polyynides. Here we show the synthesis of these salts and discuss their FT-IR spectra and thermal behaviour, which is studied by Differential Scanning Calorimetry (DSC). These properties are compared to the spectra and thermal behaviour of Cu 2C 2 and Ag 2C 2. It is shown that Cu 2C 2 can be oxidized to Cu-polyynides thereby loosing its original structure and becoming a polymeric coordinative structure. The structural changes make Cu-polyynides no more explosive than the parent Cu 2C 2. Similarly, Ag-polyynides, which decompose exothermally when heated, are not explosive compared to Ag 2C 2. The explosive decomposition of Cu 2C 2 occurs at 127°C (DSC) whereas Ag 2C 2 decomposes explosively at 169°C under the same conditions. Conversely, Cu-polyynides, when heated in the DSC, show a broad exothermal peak at about 243°C. Ag-polyynides decompose near 94°C and the release of energy is sufficiently gradual that no explosion is detected. © 2007 Springer Science+Business Media, LLC.