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abstracts
"The crystal structures of the salts of para-sulphonatocalix[8]arene with two flexible guest molecules 1,2-bis(4-pyridyl)-ethane (BPE) and 1,3-bis(4-pyridyl)-propane (BPP) are presented. para-Sulphonatocalix[8]arene molecule adopts new types of conformations: ""double facing cone"" in BPP complex and "up-flat-down" in BPE complex. Although the difference between BPE and BPP is only a presence or absence of a single carbon atom in the central bridge, the structures of their complexes with para-sulphonatocalix[8]arene are remarkably different. While the salt with BPE shows true porosity and can be compared to that of an extremely complex zeolite or to a solid state molecular Swiss Cheese, the second structure with BPP shows no porosity and is of the type of organic clay firstly observed for the sodium salt of para-sulphonato-calix[4]arene [1], and can be compared to a Gruyere Cheese. The structure of the para-sulphonatocalix[8]arene with BPE salt (Figure 1) shows a complex network of interconnecting channels of variable size, one of which contains a BPE cation effectively blocking this channel, the others contain water and solvents and are thus accessible. A total of six different channels are observed in this structure. Gas take-up has been demonstrated, to show the porous nature of the solid. The effect of a single carbon atom between the cations on the complexity of the Supramolecular Organic Framework (SOF), is remarkable. Work is currently underway to study other complexes of para-sulphonatocalix[8]arene with rigid and flexible organic cations and to open up the way to novel SOFs. Figure 1. Solvent accessible surface in para-sulphonatocalix[8]arene and 1,2-bis(4-pyridyl)-ethane complex: view along [001] axis."
abstracts
The whole range of interactions can be found between host and guest in supramolecular assemblies from ion-ion interactions, ion-dipole interactions, dipol-dipol interactions through hydrogen bonding, cation-π interactions, π-π stacking to van der Waals forces. Additionally, the same interactions exist between the supramolecular complex and its surrounding, i.e. solvent molecules, neighboring complexes, gases, etc. Recently the interest of scientists in the field of supramolecular chemistry is focused on design and synthesis of water-soluble synthetic macrocyclic ligands which are good receptors for biologically important guest molecules and can mimic the models of biological systems. Studying such complexes may provide new insight into the mechanisms of the formation of similar natural systems and as a consequence will help in better understanding the processes which occur in biological systems and in developing new materials with specific properties and functions. In this presentation the interactions which are stabilizing inclusion complexes of calix[n]arenes and cyclodextrins (host molecules) with guest molecules of biological interest, especially drug molecules will be discussed. This research was partly financed by the European Union within the European Regional Development Fund (POIG.01.01.02-14-102/09)
