In 2013, a photoswitchable antibiotic based on merging the structure of quinolones and azobenzenes was synthesized by Feringa and coworkers. The azobenzene moiety of this molecule preserved the photoisomerization ability between cis and trans forms. The tridimensional arrangement of the atoms of the cis isomers allows the quinolone moiety to bind its biological target to exhibit antibiotic activity. In contrast, the trans isomers are biologically inactive and thermodynamically more stable. Upon absorption of light with wavelength of 365 nm, the photoisomerization from trans to cis takes place and the antibiotic activity is observed for 2.08 h before disappearing. The geometries of twelve cis and four trans conformers were located and characterized. Conformational isomerization path between cis conformers is more accessible energetically through the concerted rotation of D1 and D2, while the pathway along the individual rotation of D3 has higher barriers. The transcis isomerization path on the GS is given mainly through inversion mechanisms of A1 and A2 angles, being the most likely the one along the A2 angle. The four transition states in each inversion path were located are characterized. The TSs along the inversion of A2 are connected with two minima in each side of the relaxation path, two cis and two trans isomers. The photochemical trans↔cis isomerization is associated to the deactivation pathway of the n->π* excited state through an extended seam S1/S0. The isomerization mechanism seems to be dominated by an inversion assisted rotation.

Estudio del estado fundamental y singletes excitados de un antibiótico azoquinolona activado con luz mediante la teoría del funcional de la densidad

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