Supramolecular Chemistry of Carbenes and Nitrenes

Carbenes are highly reactive intermediates. The carbon atom in a carbene contains only two instead of the normal four bonds. It is the driving force of such a divalent carbon to gain back its tetravalency and fill up its electron octet which makes this species so reactive. Six decades of divalent carbon chemistry have provided us with a vast repertoire of new and unusual reactions. It is important to harness and put to work these highly reactive species to achieve difficult synthetic tasks other reactive intermediates cannot easily perform. Supramolecular chemistry is a science still in its infancy. We generate carbenes (guests) within the confinement of other molecules (hosts) such as cyclodextrins (a class of complex cyclic sugars), and zeolites (various natural or synthesized silicates with cavities). First a carbene precursor has to be included into the host. After formation of this guest-host complex, the carbene is generated by photolysis. Nitrenes are the nitrogen containing relatives of carbenes. Since the lifetime of both reactive species is enhanced due to the surrounding confinement and the lowered chance to meet with another molecule, the reactions can become more selective. Even reactions take place which are not observed in solution. While nature very often does chemistry in confined spaces in the solid state, until now organic chemistry is mostly performed in solution. This leads to less selective reactions. In addition we study the structural microenvironment guest and host experience with sensitive analytical tools. This project in its broader sense belongs to the field of "molecular life sciences" with our activities focussed on studies on reactivity and molecular recognition in supramolecular systems.