From dicopper acetylide to carbyne

Abstract

Freshly prepared dicopper acetylide, air-aged and Cu 2+ oxidized samples have been studied by FTIR and electronic spectroscopy. There is some evidence about the polymeric and semiconductive nature of dicopper acetylide, and it is proposed to represent this compound by the general formula (Cu2 C2 · nH2O)x in which n=0.5–1 and x is unknown but large. It has been found that upon oxidation, the acetylide ion C22+ in copper acetylide undergoes a coupling reaction with formation of a diacetylene derivative and/or its higher homologues. No definitive evidence about the presence of cumulenic isomers has been found. After hydrolysis of dicopper acetylide in HCl, acetylene (the main product) together with a mixture of polyynes having the general formula H(CC)nH with n=1, 2, 3, 4, 5, 6 has been identified by electronic spectroscopy. The carbonaceous insoluble matter, obtained from aged/oxidized dicopper acetylide, hydrolyzed in HCl is carbyne as indicated by the FTIR band at 2200 cm−1. It has been shown that carbyne is also formed by oxidizing dicopper acetylide with H2O2 in aqueous ammonia suspension (FTIR bands at 2203 and 2139 cm−1), and is recovered as insoluble carbonaceous matter. Carbyne is also formed by thermal decomposition of dicopper acetylide in vacuo. Under these conditions, carbyne is a fluffy, very fine carbon powder having a high tint strength, whose FTIR spectrum shows bands at 2220 and 2200 cm−1 due to triple bond stretching vibrations. Volatile compounds are sublimable from carbyne and have been studied by electronic spectroscopy. © 1999 Society of Chemical Industry