Photophysics and luminescence switching properties of a series of photochromic styrylbenzene-terpyridine conjugate: Experimental and DFT/TD-DFT investigation

Abstract Joint experimental and computational investigation have been carried out in this work with regard to photophysical and photo-isomerization behavior of a series of photochromic terpyridine derivatives covalently coupled with styrylbenzene unit. Several electron-donating and electron-accepting groups were incorporated in the compound, tpy-pvp-X (X = H, Me, Cl, NO 2 , and Ph) to tune their photophysical as well photo-isomerization behaviors. All the compounds underwent trans- to- cis isomerization upon interaction with UV light with substantial changes in their absorption and luminescence spectra. Reversal of cis to trans forms were also achieved upon interacting with visible light. Trans- to- cis isomerization leads quenching of luminescence, while backward cis- to- trans isomerization gives rise to restoration of the original luminescence. Thus, "on-off" and "off-on" emission switching was made possible upon alternate interaction of the compounds with UV and visible light. Interestingly, the photochromic and photo-isomerization behaviors of the compounds are strongly influenced by the presence of acid. Detailed kinetic and thermodynamic aspects of the photo-isomerization process were also addressed in this study.