A Three‐Dimensional Dynamic Supramolecular “Sticky Fingers” Organic Framework

Engineering high‐recognition host–guest materials is a burgeoning area in basic and applied research. The challenge of exploring novel porous materials with advanced functionalities prompted us to develop dynamic crystalline structures promoted by soft interactions. The first example of a pure molecular dynamic crystalline framework is demonstrated, which is held together by means of weak “sticky fingers” van der Waals interactions. The presented organic‐fullerene‐based material exhibits a non‐porous dynamic crystalline structure capable of undergoing single‐crystal‐to‐single‐crystal reactions. Exposure to hydrazine vapors induces structural and chemical changes that manifest as toposelective hydrogenation of alternating rings on the surface of the [60]fullerene. Control experiments confirm that the same reaction does not occur when performed in solution. Easy‐to‐detect changes in the macroscopic properties of the sample suggest utility as molecular sensors or energy‐storage materials.     

Subvalenz bei elektropositiven s‐Block‐Metallen. Unmögliches möglich gemacht

The preparation of subvalent electropositive metal compounds succeeds in general by means of three different concepts: i) Stabilization can be achieved by delocalization of electrons in metallic matrices. A formal subvalence results from the total formula, whereas on closer examination of the bonding situation an expected “normal” valence of the metal atoms according to the octet rule can be concluded. ii) According the rules of determination of the oxidation state a formal subvalence arises from the formation of homonuclear element‐element bonds or metal clusters. However, in the case of M₂²⁺ units a normal valence is realized (which is well‐known in the chemistry of mercury as Hg₂²⁺, e.g. calomel Hg₂Cl₂). iii) The stabilization of subvalent metals with the aid of expanded π*‐systems of aren ligands succeeds when the energy lies between the two first ionization energies of the alkaline earth metal.