Supramolecular architectures of metal–organic host–guestcompounds

Metal–organic frameworks are a class of materials with new and interesting properties (Angew Chem Int Ed 43:2334, 2004; Coorg Chem Rev 38:1213, 2009; Adv Mater 23:249, 2011). In particular, porous metal organic systems are attracting considerable interest because of their potential use as sensors, catalysts and, in general, in host–guest chemistry (Acc Chem Res 43:1115, 2010). The so-called ‘‘wheel and axle’’ compounds play an important role in the developing of supramolecular chemistry and there are a lot of studies dealing with their inclusion properties and host–guest chemistry (Comprehensive supramolecular chemistry, 1996). Classical ‘‘wheel and axle’’ molecules have a long, thin, central part (the axle) with two bulky ends (the wheels). Here, new compounds with host properties are described, that we called ‘‘wheel and axle metal–organic’’ diols (WAMOD), that are decorated with OH groups in the wheel. In particular, their clathration properties are discussed in connection with their crystal structures. A modular strategy is applied to obtain WAMODs: coordination chemistry is used together with soft interactions (H-bond, p–p interaction), with the aim to realize a dynamic framework that is able to reversibly capture and release a guest. The coordination bond is robust and permits to obtain WAMODs with different arrangements of the axle; the hydrogen bonds and/or the other soft interactions are responsible for the thin adjustments in the crystal packing that allow reversible adsorption/desorption of the guest.