Effect of N-methylation on both ground and excited states properties of 1-(9-anthryl)-2-(2-benzothiazolyl) ethene

1-(9-Anthryl)-2-(2-benzothiazolyl)ethene and its salt were synthesized to study the effect of quaternarization of the nitrogen atom of benzothiazole moiety on both ground and excited states properties such as spectral characteristics in different solvents and the geometrical and electronic structures. Dual emission was observed in both compounds which originated from the involvement of locally excited (LE) and twisted intramolecular charge transfer (TICT) or intramolecular exciplex formation in excited state. Semiempirical molecular orbital calculations (PM3 and ZINDO/CI) were employed to calculate the geometrical and electronic structures of the investigated compounds in ground and excited states as well as their electronic transitions. The direction of the intramolecular charge transfer was explored via the charge distribution on the individual molecular subunits in both ground and excited states, and from the orbital topologies of the HOMO and LUMO levels of the investigated compounds.