Computational Modeling of Spectral Properties of Azobenzene Derivatives

Azobenzenes have been noted for their ability to undergo isomerization between the straight trans isomer and the bent cis isomer with visible light and UV irradiation, respectively. Their photochemically induced isomerization make them highly useful in optical switching devices. Time-dependent density functional theory (TDDFT) can model highly complex molecules like azobenzenes accurately, efficiently, and cost-effectively. In this study, TDDFT was used for the first time to model the absorption spectra of several azobenzene derivatives. The results show a reasonably good association between the theoretical and experimental values for the absorbance spectra of the azobenzenes. The ultimate goal is to use azobenzenes as terminal functional groups attached to nickel dithiolene metal complexes (which are well known to have an intense near IR absorbance band) to create photoswitchable absorbers with high sensitivity in the near IR region. Such systems are of special interest for liquid crystal device applications for near IR optical switching, modulation, and sensor protection applications.