C-symmetric phosphangulene derivatives feature planar chirality with high inversion barrier due to the phosphorus atom. Chiral phosphangulenes have been extensively studied in recent years and have been reported to show exceptionally characteristic chiroptical properties, which are extraordinarily large values of anisotropy factor. In this study, phosphangulenes having three azobenzene moieties were designed and synthesized and their chiroptical properties were controlled upon photoisomerization of azobenzenes. The phosphangulenes having three azobenzene moieties exhibit the significant decrease of the Cotton effect upon trans-to-cis photoisomerization. This decrease was not merely due to a reduction in absorbance; calculation of the anisotropy factor revealed that the intrinsic chiral properties themselves had changed. TD-DFT calculations indicated that the observed circular dichroism originates from exciton coupling among the three azobenzene moieties. In addition, the effect of exciton coupling was found to decrease markedly upon isomerization of azobenzene to the cis form. In particular, exciton coupling implies a synergistic interaction among multiple azobenzene units, suggesting that the chiroptical properties change nonlinearly as the number of cis isomers increases due to this synergistic effect.
Keywords: TD DFT, azobenzene, circular dichroism, exciton coupling, phosphangulene, photoisomerization, planar chirality
Chirality
Journal Article
English
41999180
Guideline Central and select third party use “cookies” on this website to enhance the user experience.
This technology helps us gather statistical and analytical information to optimize the relevant content for you.
The user also has the option to opt-out which may have an effect on the browsing experience.