Procházková Eliška, Čechová Lucie, Kind Jonas, Janeba Zlatko, Thiele Christina M, Dračínský Martin
Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610, Prague 6, Czech Republic.
Clemens-Schöpf Institut für Organische Chemie und Biochemie, Technische Universität Darmstadt, Alarich-Weiss Strasse 16, 64287, Darmstadt, Germany.
Chemistry. 2018 Jan 9;24(2):492-498. doi: 10.1002/chem.201705146. Epub 2017 Dec 4.
NMR spectroscopy with in situ irradiation uncovered unique photoswitchable intramolecular hydrogen bonds (IMHBs) in 5-phenylazopyrimidines with two hydrogen bond donors. These compounds form two stable rotamers, each with one IMHB, and the rotamer ratio changes reversibly upon UV or visible light irradiation. Strong substituent dependence of photoinduced structural changes was observed; using suitable substituents, orthogonal photoswitching can be achieved. For example, whereas UV irradiation caused switching between the two rotamers of the trans isomer of a compound with electron-donating methoxy substituent, visible light enabled to obtain the cis photoisomer. No cis isomer was detected for compounds with electro-neutral or electron-accepting substituents, but photoswitching between the two trans isomers was observed. On the other hand, compounds without hydrogen-bond donors or with one donor only formed stable cis isomers. A mechanism of the photoswitching was proposed by DFT computations.
原位辐照的核磁共振光谱揭示了具有两个氢键供体的5-苯基偶氮嘧啶中独特的可光开关分子内氢键（IMHBs）。这些化合物形成两种稳定的旋转异构体，每种都有一个IMHB，并且旋转异构体比例在紫外或可见光照射下可逆变化。观察到光诱导结构变化对取代基有强烈依赖性；使用合适的取代基，可以实现正交光开关。例如，具有供电子甲氧基取代基的化合物的反式异构体的两个旋转异构体之间的切换是由紫外光照射引起的，而可见光则能得到顺式光异构体。对于具有电中性或吸电子取代基的化合物，未检测到顺式异构体，但观察到两个反式异构体之间的光开关。另一方面，没有氢键供体或只有一个供体的化合物形成稳定的顺式异构体。密度泛函理论计算提出了光开关的机制。
