Constructing π-Stacked Supramolecular Cage Based Hierarchical Self-Assemblies via π···π Stacking and Hydrogen Bonding.

ABSTRACT

Constructing supramolecular cages with multiple subunits via weak intermolecular interactions is a long-standing challenge in chemistry. So far, π-stacked supramolecular cages still remain unexplored. Here, we report a series of π-stacked cage based hierarchical self-assemblies. The π-stacked cage (π-MX-cage) is assembled from 16 [MXL]+ ions (M = Mn2+, Co2+; X = Br-, SCN-, Cl-; and L = tris(2-benzimidazolylmethyl)amine) via 18 intermolecular π-stacking interactions. The tetrahedral cage, consisting of four [MXL]+ ions as the vertexes and six pairs of [MXL]+ ions as the edges, features 48 exterior N-H hydrogen bond donors for hydrogen bond formation with guest molecules. By variation of the M2+/X- pair, the π-MX-cage demonstrates unique versatility for incorporating a wide variety of species via different hydrogen-bonding modes during the assembly of hierarchical superstructures. In specific, the π-MnBr-cages encapsulate acetonitrile (CH3CN) or cis-1,3,5-cyclohexanetricarbonitrile (cis-HTN) molecules in the central voids, while a core-shell tetrahedral inorganic cluster [Mn(H2O)6]@([Mn(H2O)4]4[Br42-]6) (Mn@Mn4-cage) is captured within the interstitial regions between cages. The π-CoSCN-cages are capable of stabilizing reactive sulfur-containing species, such as S2O42-, S2O62-, and HSO3- ions, in the hierarchical superstructure. Finally, H2PO4- ions are incorporated between π-CoCl-cages, resulting in an inorganic mesoporous framework. These results provide insights into further exploring the chemistry and hierarchical assembly of supramolecular cages based on π-π stacking intermolecular interactions.