Design and synthesis of multi-component 18π annulenic fluorofullerene ensembles suitable for donor-acceptor applications

A series of trannulene (all-trans annulene) derivatives of [60]fullerene have been prepared by reacting C60F18 with methanetricarboxylate esters that incorporate a range of photoactive functions. All the compounds have the intense emerald-green colour of fullerene trannulenes, characterised by strong bands at ca. 612 and 667 nm. Single crystal X-ray studies show that the packing varies with the nature of the addend, attributable to differing steric effects. UV/vis absorption spectra display transitions of the respective fullerene and addend models, indicating absence of electronic interactions between them in the ground state. These now provide an extensive series for testing photoactive (light-harvesting) properties, with the exceptional properties of having strong visible light absorption. Their exceptional stability is attributed to the 18pi aromatic circuit, inability to undergo nucleophilic substitution without disrupting this circuit, and a curved cage region that is shielded to reagents by the three bulky addends.