Porous Molecular Crystals by Macrocyclic Coordination Supramolecules

In this study, we show how the combination of metal ions, counter-anions and opportunely functionalized and preorganized ligands gives rise to two distinct supramolecular isomers, coordination polymeric chains and hexameric macrocycles. The hexamers then aggregate to form a cubic structure exhibiting permanent microporosity. The supramolecular assemblies are formed with Ag⁺, thioether functionalized bis­(pirazolyl)­methane ligands and CF₃SO₃^–/PF₆^– as the counter-anions. Five different ligands were prepared by modifying the peripheral thioether moiety with naphthyl, methoxy, <i>m</i>-Me, <i>p</i>-Me and F groups (L^SNf, L^SPhOMe, L^SPhm‑Me, L^SPhp‑Me, and L^SPhF). Helicoidal coordination polymeric chains are formed with CF₃SO₃^– (general formula [Ag­(L)]_<i>n</i>(CF₃SO₃)_<i>n</i>), whereas macrocyclic hexamers are formed with PF₆^– (general formula [Ag­(L)]₆(PF₆)₆). The macrocycles self-assemble into ordered capsules with the shape of a tetrahedron, and the overall framework is sustained by Ag⁺···(PF₆^–)···Ag⁺ contacts. The capsules generate a highly symmetric structural arrangement, which is characterized by permanent microporosity arising from two distinct types of microporous chambers in the structure. The gas absorption isotherms show that the materials can selectively adsorb CO₂ and N₂O over CH₄ and N₂. The modulation of the microporosity of the materials is achieved by the different thioether functionalization of the ligands L^SNf, L^SPhOMe, L^SPhm‑Me, and L^SPhF. The diffusion and localization of the gas molecules within the cavities were investigated by 2D ¹H–¹³C solid state NMR on samples loaded with enriched ¹³CO₂, showing that both types of cavities are accessible to guest molecules from the gas phase