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Supramolecular chemistry studies the weak, non-covalent inter-molecular interactions. Many biological processes, such as the folding of DNA-double helix is based on these reversible interactions. In supramolecular chemistry weak interactions are for example utilized to develop host-guest systems, where the larger host molecule binds the smaller target molecule, the guest. Suitable host molecules can have applications in extraction, ion transport or in sensing.

In this dissertation three different receptors and their ability to bind anions was studied. Pyridine[4]arene had already shown affinity towards anions in previous studies.  Erroneously it was commonly thought that the binding of the anion would take place inside the hydrogen-bonded dimeric capsule of pyridinearene. However, in this work it was shown that the binding of the anion takes place outside the cavity. Pyridinearene was also observed to bind several guest molecules simultaneously. Neutral and cationic guests are bound inside the pyridinearene capsule, while the anionic guests are bound outside. Ion-mobility mass spectrometry had an important role in revealing the binding site of the guest molecules.

Thermodynamics favor the formation of larger capsules

The ability of pyridinearene to form hexameric capsules was also observed for the first time in gas phase and in solid state, as previously they have been detected only in solution. A more detailed study in solution by NMR spectroscopy showed that the larger hexameric capsule is a thermodynamic product, while the dimer is only a kinetic product.

Another studied receptor, cyclohexylhemicucurbit[8]uril showed to bind anions inside its cavity, with especially strong affinity towards toxic SbF6- anion. This receptor showed to be selective, as the bound anions needed to have a suitable size, shape and charge distribution. In the third type of receptors, the crown ether -urea receptors, the binding of the guest was demonstrated as an ion pair, which is energetically more favorable than binding of a single ion. These designed receptors showed to bind an ion pair, but their affinity towards anions was still lower than with cyclohexylhemicucurbitu[8]uril.

The reseaarch is published JYU Dissertations series, 2019, number 137, ISSN 2489-9003; 137, ISBN 978-951-39-7855-6 (PDF)  Link to publication:

M.Sc  Anniina Kiesilä defends her doctoral dissertation in Organic Chemistry "Supramolecular chemistry of anion binding receptors based on concave macrocycles" on Friday 11th of October 2019 at the Department of Chemistry lecture hall KEM4 at 12 o'clock. Opponent Professor is David V. Dearden from Brigham Young University, USA and Custos is Academy Research Fellow Elina Kalenius from the Ä¢¹½Ö±²¥. The doctoral dissertation is held in English.

For further information:
M.Sc Anniina Kiesilä, anniina.m.kiesila@jyu.fi
Communications officer Tanja Heikkinen, tanja.s.heikkinen@jyu.fi, puh. +358 581 3751
The Faculty of Mathematics and Science: /science/en
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