Department of Chemistry, University of Namur (UNamur) , Rue de Bruxelles 61, Namur, 5000, Belgium.
Department of Physics, King's College London , Strand, London WC2R 2LS, United Kingdom.
J Am Chem Soc. 2017 Dec 20;139(50):18271-18280. doi: 10.1021/jacs.7b09568. Epub 2017 Dec 5.
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 H NMR investigations of the photochemical and thermal isomerization kinetics show that the thermal Z → E 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 π* antibonding character. This results in a reduction of the N═N torsional barrier and thus in accelerated thermal Z → E isomerization. Combined with light-controlled E → Z isomerization, this enables controllable fractional tuning of the two configurational isomers.
研究了尿嘧啶-偶氮苯衍生物的 E/Z 异构化过程，该衍生物的碱基与苯二氮尾巴共轭，因为其能够与适当互补的 2,6-二乙酰氨基-4-吡啶配体形成三重氢键复合物。光化学和热异构化动力学的 UV-vis 和 H NMR 研究表明，形成氢键复合物后，热 Z → E 互变异构的速度加快了 4 倍。DFT 计算表明，三重氢键的形成引发了 N=N 双键的显著伸长，这是由于其π*反键性质的增加。这导致 N=N 扭转势垒的降低，从而加速了热 Z → E 异构化。与光控的 E → Z 异构化相结合，这使得两种构象异构体的分数调谐得以控制。
