Synthesis of Linear Acetylenic Carbon

Abstract

A new carbon allotrope based “sp” hybridization contaning alternating triple and single bonds (an acetylenic or linear carbon allotrope) has been prepared. Studies of small (8 to 28 carbon atoms) acetylenic carbon model compounds show that such species are quitestable (130-140°C) provided that nonreactive terminal groups or end caps, such as t-butyl, triethylsilyl, phenyl, trifluoromethyl, or nitrile groups, are present to stabilize these molecules against further reactions. Using laser based synthetic techniques in the presenceof end capping groups, similar to the conditions normally used to generate fullerenes, thermally stable acetylenic carbon species cappedwith trifluoromethyl or nitrile groups have been prepared with chain lengths in excess of 300 carbon atoms. Under these conditions, the production of fullerenes is suppressed and only a negligible quantity of fullerenes is produced. Acetylenic carbon compoundsare not particularly moisture or oxygen sensitive but are moderately light sensitive. Carbon (13C) nuclear magnetic resonance (NMR), infrared (IR) spectroscopy, and laser desorption mass spectroscopy are used to characterize these carbon chain speciesand confirm that capped acetylenic chain polymers, (-C≡C-C≡-) n, join graphite, diamond and fullerenes-nanotubes as the fourthallotrope of the element carbon.