Azopyrimidine photoswitches and their interactions with cyclodextrins

Researchers led by Eliška Procházková from IOCB Prague have found that azopyrimidine photoswitches become encapsulated into β-cyclodextrin (CD) cavity selectively via their phenyl ring. The strength of the complex is tuned by structural modification of azopyrimidine.

In the strongest complexes, the trans-to-cis isomerization proceeds inside the CD cavity. In the weak complexes, azopyrimidine in the trans isomer is complexed via the narrower primary portal and released from the CD cavity upon irradiation. Consequently, the resulting cis isomer is re-complexed through the wider secondary portal.

This research highlights the applicability of these and similar types of supramolecular assemblies as a function of the interaction strength and mutual orientation of host and guest molecules, which have been studied for the first time in cases of cyclodextrin-azenyl couples by a combined NMR spectroscopy-capillary electrophoresis-quantum chemistry approach.