Recently, we reported the synthesis of a new dicationic macrocycle that is derived from the condensation of dipyrazoles and several substituted glycoluril diethers to complete the cyclisation.1,2 The molecular skeleton of the simplest of these macrocycles has a structure in a form that resembles the form of a tiara, where the C=O groups represent the jewels at the front and the dipyrazolium the band at the back (Scheme 1). In view of the resemblance, we named this family of molecules tiara[n]uril.
These macrocycles are highly water-soluble, however, as we introduce substitution at the R group their properties can be modified. The macrocycles have molecular host properties which are dissimilar to their cucurbituril molecular relatives due to the cationic walls, with some surprises. The arc of C=O’s at the top and bottom of each portal and the known characteristic feature of the concave face of the glycoluril moieties within a cavity, but opposite a diffuse cationic wall suggested a potential for lipophilic, H-bonding and electronegative molecules as guests. The types of molecular guests that can be encapsulated will be discussed.
Adding aliphatic chains at the R group, imparts an amphiphilic nature to these macrocycles, which show micelle formation in the presence of drugs in some variation. Some other self-assembled structures are neither micelles nor vesicles and these will also be discussed.