Ligands which bind receptors giving stable supramolecular systems are of utmost importance in biotechnology and technological applications. Cucurbituril systems (CB[n], n = 5, 6, 7, 8, 10) have recently been studied as efficient supramolecular receptors for molecular recognition in water. The water environment is a challenge when designing suitable ligands, seeing as they are usually small, hydrophobic organic molecules. The best binding interactions with CB[n] can be accomplished by ligands that combine cationic and hydrophobic subunits in their structure, like for example diamondoid compounds.

We recently discovered that a complex of CB[7] with a permethylated diamantane 4,9-diamine has an association constant of 7.2·10¹⁷ M^-1 in a water solution, making it at the time the most stable cucurbituril complex ever described [1]. This complex is 143 times more stable than the previous strongest known complex of a ligand with CB[7].

In the framework of this project we prepared and characterized several diamondoid amine derivatives that were then tested as ligands for inclusion complexes with CB[n] [2]. We designed the ligands and chose the substituents by taking into account structural characteristics of CB[n], including the size of the ureido carbonyl portals and the dimensions of the hydrophobic cavity. The main goal of the project is to find optimal geometrical parameters and the best diamondoid functionalization pattern in order to realize very strong binding of these supramolecular systems in a water medium.

[1] L. Cao, M. Šekutor, P. Y. Zavalij, K. Mlinarić-Majerski, R. Glaser, L. Isaacs, Cucurbit[7]uril•Guest Pair with an Attomolar Dissociation Constant, Angew. Chem., Int. Ed. 2014, 53, 988‒993. => cover

[2] J. Hostaš, D. Sigwalt, M. Šekutor, H. Ajani, M. Dubecký, J. Řezáč, P. Y. Zavalij, L. Cao, C. Wohlschlager, K. Mlinarić-Majerski, L. Isaacs, R. Glaser, P. Hobza, A Nexus between Theory and Experiment: Non-empirical Quantum Mechanical Computational Methodology Applied to Cucurbit[n]uril•Guest Binding Interactions, Chem. Eur. J. 2016, 22, 17226‒17238. => cover

FINANCIAL SUPPORT

Croatian Academy of Sciences and Arts