Sunlight-Induced Covalent Marriage of Two Triply Interlocked Pd₆ Cages and Their Facile Thermal Separation

Abstract

A template-free triply interlocked Pd₆ cage (<b>2</b>) was synthesized by two-component self-assembly of <i>cis</i>-blocked 90° acceptor <i>cis-</i>(tmen)­Pd­(NO₃)₂ (<b>M</b>) and 1,3,5-tris­((<i>E</i>)-2-(pyridin-3-yl)­vinyl)­benzene (<b>L</b>). Assembly <b>2</b> was characterized by ¹H NMR and ESI-MS, and the structure was confirmed by X-ray crystallography, which revealed a parallel conformation of the olefin double bonds belonging to the adjacent cages in the solid state at a distance of 3.656 Å, thereby indicating the feasibility of [2+2] photochemical reaction. Two adjacent interlocked cages were covalently married together by intermolecular [2+2] cycloaddition in a single crystal-to-single crystal fashion upon exposure to sunlight/UV irradiation. Most surprisingly, the covalently married pair was easily separated thermally in aqueous medium under mild reaction conditions