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Confirmation of the Structure of Trans ‐Cyclic Azobenzene by X‐Ray Crystallography and Spectroscopic Characterization of Cyclic Azobenzene Analogs
Author(s) -
Jun Meesook,
Joshi Dhruval K.,
Yalagala Ravi S.,
Vanloon Jesse,
Simionescu Razvan,
Lough Alan J.,
Gordon Heather L.,
Yan Hongbin
Publication year - 2018
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201703126
Subject(s) - azobenzene , photoisomerization , photoswitch , chemistry , cis–trans isomerism , crystallography , x ray crystallography , crystal structure , thermal stability , molecule , proton nmr , isomerization , stereochemistry , diffraction , photochemistry , organic chemistry , optics , physics , catalysis
The photoisomerization properties of a series of cyclic azobenzene (cAb) analogs, including non‐substituted, Br‐, CN‐, carboxyl‐, and amino cAb, were compared. While the trans ‐form of these analogs show different degrees of thermal stability, no spectral changes in the absorption wavelengths were observed for amino cAb upon exposure to purple light. The 15 N NMR chemical shifts of cAb in both cis ‐ and trans ‐forms were found to show a large difference from those of aromatic azobenzene; however, the trend of difference in chemical shift is in agreement with that obtained from quantum chemical calculations. More importantly, the structure of the photoisomerization product from cis ‐cAb was confirmed to be, indeed, the trans ‐cAb by X‐ray diffraction experiments. The 15 NMR data of the cAb isomers and confirmation of trans ‐cAb through crystal structure will be of importance for future studies in the design and applications of cAb as a photoswitch.