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(mu-(NBu)-Bu-t}(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 pi systems of the unsaturated C equivalent to C and C equivalent to 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.