Host-Guest Chemistry of M12L8 Poly-[n]-catenanes: Inclusion Process by Switchable ''losed-Open'' ynamic Channels

Direct guest exchange reactions in one-dimensional (1D) poly-[n]-catenanes self-assembled by elusive M12L8 large nanocages (similar to 2600 angstrom(3) of internal volume) have never been documented. Herein, we report for the first time the guest behavior of a TPB poly-[n]-catenane (1) self-assembled from M12L8 icosahedral nanocages in the absence of permanent communicating voids. High-resolution synchrotron X-ray data obtained by means of crystal-to-crystal guest exchange reactions unambiguously demonstrate the uptake of o-dichlorobenzene and p-chloroanisole. Density functional theory calculations aimed at studying local interaction energy variation among 1D chains of catenated M12L8 cages provided insights that help us further understand the intrinsic dynamic behavior of the 1D porous rods. The guest uptake by the icosahedral M12L8 nanocages is rationalized via a switchable closed-open process considering both the weak interchain interactions and the stronger intrachain mechanical bond. Mechanistic aspects of the molecular exchange consider both the sliding motion of the 1D chains of interlocked M12L8 nanocages and the dynamic aspects of single M12L8 cages within the 1D chains (i.e., cage compression/extension) in a concerted cooperative dynamic behavior. Thermal treatment of the ZnBr2-TPB poly-[n]-catenane demonstrates that the mechanical bond remains up to similar to 500 K. The exceptional structural properties of 1 have been studied for potential applications such as selectivity of chlorobenzenes. The labile nature of the Zn-N coordination bond allows the recyclability of the TPB ligand in water, thus making these materials candidates in green chemistry applications.