A tetrameric cage with D2h symmetry through alkyne metathesis

Abstract

Shape-persistent covalent organic polyhedrons (COPs) with ethynylene linkers are usually prepared through kinetically controlled cross-coupling reactions. The high-yielding synthesis of ethynylene-linked rigid tetrameric cages via one-step alkyne metathesis from readily accessible triyne precursors is presented. The tetrameric cage contains two macrocyclic panels and exhibits D2h symmetry. The assembly of such a COP is a thermodynamically controlled process, which involves the initial formation of macrocycles as key intermediates followed by the connection of two macrocycles with ethynylene linkages. With a large internal cavity, the cage exhibits a high binding selectivity toward C70 (K=3.9×103 Lmol-1) over C60 (no noticeable binding). Clever cages: A tetrameric cage with a D2h symmetry was prepared from a C3-symmetric triyne monomer through a one-step alkyne metathesis. The tetramer consisting of two macrocyclic panels has a large internal cavity, which can selectively host C70 over C60.