Synthesis of Rotaxane Structures with Multitopic Ligands

Molecular switches are of considerable interest due to their potential applications in a wide range of fields, including electronics, sensing or medicine. Rotaxanes, i.e., mechanically interlocked molecules, consisting of a ring-shaped molecule (macrocycle) threaded onto an axle-like molecule (thread), can act as molecular switches in certain cases. Both rotaxane components are kinetically trapped as the bulky groups at both ends of the thread are usually larger than the internal diameter of the macrocycle, and therefore this complex cannot undergo dissociation. Rotaxanes can be also considered as a storage of their ring component, which expands their application potential as a complement to the systems that retain the mechanically interlocked manner. In our work, we designed three generations of ligands for the formation of cucurbit[6]uril (CB6) based rotaxane systems, whose axes are equipped with an additional high-affinity binding motif for another macrocycles, cucurbit[7]uril (CB7) and -cyclodextrin (-CD). First-generation ligands differed in the length of their central binding motif, while terminal motifs for CB6 slippage (isobutyl, IB) and binding of CB7 (1-adamantylmethyl, Ad) remained invariant. The formation of intended rotaxanes was successful only with the ligand featuring a hexyl motif, as the lengths of the others were not ideal for capturing the CB6. Structures representing second-generation ligands carried bulkier neopentyl-derived terminal moiety for CB6 slipping-on. However, these rotaxanes were not prepared either, as the neopentyl motif is too bulky and does not allow the threading of CB6 under any conditions we used. Finally, successfully assembled rotaxanes of the thirdgeneration consisted of an IB end, 1,6-hexanediammonium centre linker and variable Ad-derived terminal moieties. The difference lay in the length of the linker between the Ad cage and the positively charged nitrogen atom (from methylene to phenylenemethyl spacer). By the shortest rotaxane (with methylene linker), this thesis demonstrates that binding of CB7 to the allosteric Ad binding site, significantly increases the energy of the system which is sufficient for the mechanical barrier to be overcome. This means, that the electrostatic repulsion between the portals of the two CBn units can be employed to disassemble a rotaxane to its ring and axle components. Moreover, the kinetics of the slippingoff process can be tuned by the length of the allosteric binding site where the CB7 acts (ethylene, propylene, propenylene spacer). Finally, upon liberation from the rotaxane, the CB6 wheel can be utilized in forming complexes with other guests (i.e., spermine) present in the mixture.

ISBN:	978-80-7678-323-2
EAN:	9788076783232
Počet stran	46 stran
Datum vydání	19. 03. 2025
Pořadí vydání	První
Jazyk	anglický
Vazba	e-kniha - pdf
Autor:	Aneta Závodná
Nakladatelství	Univerzita Tomáše Bati ve Zlíně
Tématická skupina	999 - nezařazeno
	Neprodejná publikace. Publikaci je možné poptávat zde: Volně dostupné na http://hdl.handle.net/10563/56826