Guest Binding via N-H⋅⋅⋅π Bonding and Kinetic Entrapment by an Inorganic Macrocycle

Modern supramolecular chemistry is overwhelmingly based on non-covalent interactions involving organic architectures. However, the question of what happens when you depart from this area to the supramolecular chemistry of structures based on non-carbon frameworks remains largely unanswered, and is an area that potentially provides new directions in molecular activation, host-guest chemistry, and biomimetic chemistry. In this work, we explore the unusual host-guest chemistry of the pentameric macrocycle [{P(μ-N^t Bu}₂ NH]₅ with a range of anionic and neutral guests. The polar coordination site of this host promotes new modes of guest encapsulation via hydrogen bonding with the π systems of the unsaturated C≡C and C≡N bonds of acetylenes and nitriles as well as with the PCO^- anion. Halide guests can be kinetically locked within the structure by oxidation of the phosphorus periphery by oxidation to P^V . Our study underscores the future promise of p-block macrocyclic chemistry.