X-ray structural studies on weak, non-covalent interactions in supramolecular compounds

Abstract

22 novel crystal structures of organic, supramolecular compounds and their analysis are reported. The structures present examples of a few of the most typical classes of compounds in supramolecular chemistry, i.e. crown ethers, cyclophanes, calix[4]arenes and resorcin[4]arenes. Crown ether structures (original publications I-IV; 14 structures) present an example of host-guest complexes in which hydrogen bonding interactions play a major role but in which other weak interactions also contribute to the complexation. Cyclophane structures incorporating bisphenol A units (publications V and VI; four structures) demonstrate the importance of the preorganisation and the suitable size of the cavity for complexation. The third class of potential, supramolecular macrocyclic host compounds, calix[4]arenes (publications VII and VIII; two structures), showed no molecular or clathrate inclusion of the solvent thus confirming the unsuitability of this type of calix[4]arenes for complexation. However, the crystal structures provided valuable information for the designing of further synthetic steps. The crystal structure of ethyl resorcin[4]arene cocrystallised with melamine (publication IX; two structures) revealed an exceptional guest-induced conformational change of the resorcinarene from crown to boat conformation. Special attention in all these studies has also been paid to the investigation of crystal packing and the weak intermolecular forces affecting it in addition to the sterical effects. As an introduction to the subject a short review of the literature will present the most typical weak interactions and the classes of macrocyclic, supramolecular hosts discussed in the experimental part.