Probing Near-infrared Absorbance of E and Z Diazene Isomers via Antiaromaticity

The photoswitching behaviors of heteroarylazos and azobenzeneshave attracted considerable interest due to their applications frommaterial science to pharmacology. However, the use of UV light limitstheir application, especially in biomedicine and photopharmacology.In this work, using several aromaticity descriptors, including anisotropyof the induced current density analysis and nucleus-independent chemicalshifts, we systematically investigate the relationship between anti-aromaticityand the absorption of a series of heterocyclic azos. We have demonstratedthat the antiaromatic heterocycles substituted with diazenes enablethe significant red shifts of the n & RARR; & pi;* and & pi;& RARR; & pi;* transition bands of E and Z isomers via density functional theory calculations. Moreover,introducing substituents into heterocycles could further tune theabsorption. Finally, the & lambda;(max) of the first transitionbands of the E (ca. 1026 nm) and Z isomers (ca. 1167 nm) of azos is achieved in the near-infrared region.

Automated summary

The use of UV light limits the applications of heteroarylazos and azobenzenes, especially in biomedicine and photopharmacology. In this study, we systematically investigated the relationship between anti-aromaticity and the absorption spectra of a series of heterocyclic azos using density functional theory calculations. We demonstrated that antiaromatic heterocycles substituted with diazenes enable significant red shifts of the absorption spectra of E and Z isomers, and the introduction of substituents further tunes the absorption. Ultimately, we achieved absorption of the first transition bands of E and Z isomers of azos in the near-infrared region.