Functionalization of Fullerenes with Cyclopentadienyl and Anthracenyl Capped Polymeric Building Blocks via Diels-Alder Chemistry.

Cyclopentadienyl (Cp) capped polymers [polyethylene glycols (PEGs), $\overline M _{\rm n}$ = 2 000 g · mol(-1) ], react readily with fullerenes in a 1:1 molar ratio (relative to the amount of fullerenes and Cp-end groups) at ambient temperature within 5 min in the absence of any catalyst in a Diels-Alder (DA) reaction to provide fullerene-PEG hybrids. Similarly, anthracenyl capped PEGs react with fullerenes (in a 1:3 molar ratio) in DA reactions to yield the corresponding hybrids, albeit over a period of 1.5 h at 80 °C and a lesser conversion. The efficiency of the transformation is monitored via electrospray ionization mass spectrometry (ESI-MS), demonstrating that the fullerenes can be transformed into polymer hybrids; most efficiently when Cp-functional polymer is used as the diene. In addition, the obtained hybrids were subjected to UV/Vis as well as thermogravimetric analysis further underpinning the formation of mono-substituted C(60) -PEG hybrids [wt.-%(exp) 70 ± 5 (PEG), 30 ± 5 (C(60) ), wt.-%(theo) 68 (PEG), 32 (C(60) )].