Coalescence reactions of fullerenes

Abstract

THE production of fullerene molecules typically involves extreme high-temperature conditions (electric arcs¹, flames² or resistive heating³), and the reactive processes involved are poorly understood. Once separated^4,5, these molecules can undergo several important reactions, including formation of charge-transfer^6,7 and adduct^8,9 compounds, and the encapsulation of atoms^10–12. Here we present evidence for coalescence reactions between fullerene molecules: mass spectrometric measurements on hot, dense vapours of small fullerenes (C₆₀ and C₇₀) reveal the formation of stable higher fullerenes which are multiples of the initial masses. The heat of coalescence is released through emission of small, even-numbered fragments which, in a very dense vapour, are efficiently captured by other coalesced fullerenes. These findings have implications for the mechanisms of fullerene formation and growth, and may open the way to new synthetic routes to selected higher fullerenes and encapsulation compounds.