Tunable Photoswitching in Norbornadiene (NBD)/Quadricyclane (QC) - Fullerene Hybrids
P Lorenz and F Wullschlager and A Ruter and B Meyer and A Hirsch, CHEMISTRY-A EUROPEAN JOURNAL, 27, 14501-14507 (2021).
With respect to molecular switches, initializing the quadricyclane (QC) to norbornadiene (NBD) back-reaction by light is highly desirable. Our previous publication provided a unique solution for this purpose by utilizing covalently bound C-60. In this work, the fundamental processes within these hybrids has been investigated. Variation of the linker unit connecting the NBD/QC moiety with the fullerene core is used as a tool to tune the properties of the resulting hybrids. Utilizing the Prato reaction, two unprecedented NBD/QC - fullerene hybrids having a long- rigid and a short-rigid linker were synthesized. Molecular dynamics simulations revealed that this results in an average QC-C-60 distance of up to 14.2 angstrom. By comparing the NBD-QC switching of these derivatives with the already established one having a flexible linker, valuable mechanistic insights were gained. Most importantly, spatial convergence of the QC moiety and the fullerene core is inevitable for an efficient back-reaction.
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