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.