A quasiracemic strategy for controlling the guest-inclusion capability of metal–organic structures

Coordination polymers that precisely incorporate two closely related ligands differing only in their substituents are often difficult to construct because such ligands tend to be randomly distributed within the framework. In this study, we demonstrate a quasiracemic strategy that enables well-defined incorporation of differently substituted ligands into a single coordination polymer. Given that racemates crystallize more readily than single enantiomers owing to the complementary of mirror-imaged structures, a quasiracemic pairs of methyl- and ethyl-substituted bis(4-pyridyl) ligands assembles with Cu(I) iodide to form a double-bridged polymer containing acetonitrile molecules within its channel structure. Intriguingly, this polymer constructed from the quasiracemic ligands exhibits unique adsorption behavior toward benzonitrile compared with the analogue polymers constructed from the corresponding racemic methyl- or ethyl-substituted ligands. This study provides a new design principle for controlling guest inclusion capability of metal–organic structures.