White Phosphorus Is Air-Stable Within a Self-Assembled Tetrahedral Capsule

The air-sensitive nature of white phosphorus underlies its destructive effect as a munition: Tetrahedral P₄ molecules readily react with atmospheric dioxygen, leading this form of the element to spontaneously combust upon exposure to air. Here, we show that hydrophobic P₄ molecules are rendered air-stable and water-soluble within the hydrophobic hollows of self-assembled tetrahedral container molecules, which form in water from simple organic subcomponents and iron(II) ions. This stabilization is not achieved through hermetic exclusion of O₂ but rather by constriction of individual P₄ molecules; the addition of oxygen atoms to P₄ would result in the formation of oxidized species too large for their containers. The phosphorus can be released in controlled fashion without disrupting the cage by adding the competing guest benzene.