The first chemical modification on the endohedral HF@C60 is reported. In particular, the isomerization from optically pure (2S,5S)-cis-pyrrolidinofullerene 2b to (2S,5R)-trans-pyrrolidinofullerene 2b has been studied and compared with empty C60 (2a) and endo-hedral H2O@C60 (3). Interestingly, the incarcerated HF molecule contributes to increase the isomerization rate through a H-bonding assistance involving weak hydrogen bonding without affecting the final cis-trans ratio or promoting the loss of enantioselective control through the retro-cycloaddition reaction. The comparative study shows a kinetic order for the isomerization process of H2O@C60 ˃ HF@C60 ˃ C60, thus confirming the effect of the incarcerated species on the zwitterionic intermediate stability

This work was supported by the European Research Council ERC-320441-Chirallcarbon, Ministerio de Economía y Competitividad (MINECO) of Spain (project CTQ2014-52045-R) and the CAM (FOTOCARBON project S2013/MIT-2841). R.J.W. and S.A. thank the Engineering and Physical Sciences Research Council (UK) for funding this work (EP/1029451, M001962, M001970) including core capability (EP/K039466). M.I. thanks to Ministerio de Economía y Competitividad (MINECO) of Spain (Juan de la Cierva-Incorporación IJCI-2014-19320). We are also grateful for financial support from the Spanish MINECO (CTQ2014-54306-P, CTQ2014-59212-P, and RyC contract RYC-2014-16846 to S.O.), the Catalan DIUE (2014SGR931, ICREA Academia 2014 Award to M.S. and XRQTC), and the FEDER fund (UNGI10-4E-801). M.G.-B. thanks the Ramón Areces Foundation for a Postdoctoral Fellowship and S.O. the European Commission for CIG project (FP7-PEOPLE-2013-CIG630978), and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (ERC-2015-StG-679001). Excellent service from computational centers CSUC and BSC-CNS is acknowledged. NM thanks to EC FP7 ITN “MOLESCO” Project No. 606728