Fluorescence enhancement from self-assembled aggregates: Substituent effects on self-assembly of azobenzenes

The preparation of a simple azobenzene derivatives para-substituted with electrons-donating (EDGs) or electron-donating groups (EWGs) to get insight into the determinants of spontaneous self-assembly of azobenzene is presented. The azobenzene compounds began to display blue fluorescence as the azobenzene solution was continuously exposed to ultraviolet (UV) radiation at 365 nm. The formation of self-assembly aggregates resulted in significant changes in UV-vis absorption spectra before and after UV light irradiation. The results show that UV-exposedazobenzene molecules increases with increasing electron-donating abilities of the substituents, and the fluorescence enhancement is attributed to the light-driven self-assembly of cis-azobenzenes showing sufficient lifetime and a larger dipole moment.