American Chemical Society
ja7b09568_si_005.pdf (3.71 MB)

Toward Fractioning of Isomers through Binding-Induced Acceleration of Azobenzene Switching

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journal contribution
posted on 2017-10-24, 00:00 authored by Rosaria Vulcano, Paolo Pengo, Simone Velari, Johan Wouters, Alessandro De Vita, Paolo Tecilla, Davide Bonifazi
The E/Z isomerization process of a uracil–azobenzene derivative in which the nucleobase is conjugated to a phenyldiazene tail is studied in view of its ability to form triply H-bonded complexes with a suitably complementary 2,6-diacetylamino-4-pyridine ligand. UV–vis and 1H NMR investigations of the photochemical and thermal isomerization kinetics show that the thermal ZE interconversion is 4-fold accelerated upon formation of the H-bonded complex. DFT calculations show that the formation of triple H-bonds triggers a significant elongation of the NN double bond, caused by an increase of its πg* antibonding character. This results in a reduction of the NN torsional barrier and thus in accelerated thermal ZE isomerization. Combined with light-controlled EZ isomerization, this enables controllable fractional tuning of the two configurational isomers.