Čechová Lucie, Kind Jonas, Dračínský Martin, Filo Juraj, Janeba Zlatko, Thiele Christina M, Cigáň Marek, Procházková Eliška
Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo nám. 2 , Prague 16610 , Czech Republic.
Clemens-Schöpf-Institut für Organische Chemie und Biochemie , Technische Universität Darmstadt , Alarich-Weiss-Strasse 16 , Darmstadt 64287 , Germany.
J Org Chem. 2018 Jun 1;83(11):5986-5998. doi: 10.1021/acs.joc.8b00569. Epub 2018 May 11.
The photoswitching behavior of 5-phenylazopyrimidines was investigated by optical methods and NMR spectroscopy with in situ irradiation sustained by mathematical modeling and DFT calculations. Irradiation of various compounds with electron-donating groups on the pyrimidine ring and substituents with electron-withdrawing as well as electron-donating substituent in the para-position of the phenyl ring were examined. All compounds could be successfully converted to the cis isomer; this isomerization and the subsequent thermal fading were studied. Switching cycles can be repeated without signs of photodegradation for most of the compounds, which makes them adept to molecular photoswitches. Interestingly, the chloro and cyano derivatives can be switched without UV light, which makes them vis(π → π*)-vis(n → π*) photoswitches. Surprisingly equal trans-to- cis photoisomerization quantum yields for π → π* and n → π* excitation indicate the blocking of the inversion pathway following π → π* excitation. In contrast to that, DFT computations suggest the inversion mechanism for the reverse thermal cis-to- trans isomerization of 5-phenylazopyrimidines.
通过光学方法和核磁共振光谱对5-苯基偶氮嘧啶的光开关行为进行了研究，采用数学建模和密度泛函理论计算实现原位照射。研究了嘧啶环上带有供电子基团以及苯环对位带有吸电子和供电子取代基的各种化合物的照射情况。所有化合物都能成功转化为顺式异构体；对这种异构化以及随后的热褪色进行了研究。对于大多数化合物，开关循环可以重复而无光降解迹象，这使其适用于分子光开关。有趣的是，氯代和氰基衍生物无需紫外光即可切换，这使其成为可见（π→π*）-可见（n→π*）光开关。令人惊讶的是，对于π→π和n→π激发，反式到顺式光异构化量子产率相等，这表明π→π*激发后反转途径受阻。与此相反，密度泛函理论计算表明5-苯基偶氮嘧啶反向热顺式到反式异构化的反转机制。
