Photophysical properties of Schiff’s bases from 3-(1,3-benzothiazol-2-yl)-2-hydroxy naphthalene-1-carbaldehyde

• Synthesis of Schiff’s bases from 3-(1,3-Benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde.
• Photophysical properties of all Schiff’s bases have been studied experimentally in different solvents.
• Photophysical properties of Schiff’s base 6a have been investigated theoretically and correlated to the experimental results.
• DFT and TD-DFT computation have been used to investigate the structural parameters and geometry of 6a.

A series of novel Schiff’s bases have been synthesized from 3-(1,3-benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde. The presence of hydroxyl group ortho to the benzothiazolyl group as well as the imine linkage lead to the occurrence of excited state intramolecular proton transfer process. The computational strategy was used to study the ESIPT process of the synthesized Schiff’s bases, which revealed surprisingly that the keto form predominantly exists in the ground state contradicting the ESIPT process. Density functional theory and time dependent density functional theory have been used to investigate the structural parameters and photophysical properties in different solvents of one of the Schiff’s bases. The experimental results correlate well with the computed results. All Schiff’s bases show good thermal stability.

Presence of hydroxyl group at ortho position to benzothiazole ring as well as imine linkage may lead to the existence of ESIPT process. But computational study of one of the Schiff’s bases reveals that keto form is more stable than enol form at ground state in gas as well as in solvent phase. Thus ESIPT process does not exist in synthesized Schiff’s bases.Figure optionsDownload as PowerPoint slide