Using a non-labile Co (III) metal template and click reaction followed by de-metalation, synthesis of [2], linear [3], and radial [4] catenane has been achieved. Synthesized templated linear [2] catenane has an additional metal binding site for the synthesis of higher-order catenane through post-functionalization.

Abstract

Design and synthesis of higher order catenane are unexpectedly complex and involve precise cooperation among the precursors overcoming competing and opposing interactions. We achieved synthesis of [2], linear [3], radial [4] in a one-pot reaction by consecutive ring closing through click reactions. This synthesis gave three isolable products due to two, four, and six-click reactions between suitable coupling partners. Yields of the isolate templated-catenane decrease from lower to higher-ordered catenane (40 %, 12 %, and 4 %), probably due to the bite angle as well as the flexibility of the reacting partners. Removal of templating cobalt(III) ion leads to the formation of fully organic [2], linear [3], and radial [4]catenane. These synthesized catenanes were purified by column chromatography and characterized by ¹H-NMR, ¹³C-NMR, and ESI-MS spectroscopy. The synthesized catenanes have free binding sites suitable for post-functionalization and may be used for the synthesis of higher-ordered catenane.