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.

In irons bound: Linear diamine and formylpyridine subcomponents form a tetrahedral cage with iron(II) in water (see scheme). This cage traps hydrophobic guests with high specificity within a rigid cavity, isolating them from the aqueous environment. The cage may be broken, releasing the guest, upon the addition of a triamine. It may also be unlocked by adding acid, allowing the guest to be reversibly released until base is added, relocking it within.

A general method for preparing Fe(4)L(4) face-capped tetrahedral cages through subcomponent self-assembly was developed and has been demonstrated using four different C(3)-symmetric triamines, 2-formylpyridine, and iron(II). Three of the triamines were shown also to form Fe(2)L(3) helicates when the appropriate stoichiometry of subcomponents was used. Two of the cages were observed to have nearly identical Fe-Fe distances in the solid state, which enabled their ligands to be coincorporated into a collection of mixed cages. Only one of the cages combined a sufficiently large cavity with the sufficiently small pores required for guest binding, taking up a wide variety of guest species in size- and shape-selective fashion.

With the growing interest in renewable energy and global warming, it is important to minimize the usage of hazardous chemicals in both academic and industrial research, elimination of waste, and possibly recycle them to obtain better results in greener fashion. The studies under the area of mechanochemistry which cover the grinding chemistry to ball milling, sonication, etc. are certainly of interest to the researchers working on the development of green methodologies. In this review, a collection of examples on recent developments in organic bond formation reactions like carbon–carbon (C–C), carbon–nitrogen (C–N), carbon–oxygen (C–O), carbon–halogen (C–X), etc. is documented. Mechanochemical syntheses of heterocyclic rings, multicomponent reactions and organometallic molecules including their catalytic applications are also highlighted.

Lineare Diamin‐ und Formylpyridin‐Einheiten bilden mit Eisen(II) einen tetraedrischen Käfig (siehe Schema), der hydrophobe Gastspezies hoch spezifisch in seinem Hohlraum aufnimmt und von der wässrigen Umgebung abschirmt. Beim Öffnen des Käfigs durch Zusatz eines Triamins wird die eingeschlossene Spezies freigesetzt. Alternativ zerfällt der Käfig bei Zugabe von Säure, doch dieser Prozess kann durch Base rückgängig gemacht werden, sodass die Gastspezies reversibel freigesetzt und eingeschlossen wird.