Molecular aggregation and photochemical Z/E isomerization of 1-methy-2-[2-(9-phenantheryl)ethenyl] benzothiazolium iodide

The steady state absorption and fluorescence spectra of a hemicyanine dye namely, 1-methy-2-[2-(9-phenantheryl)ethenyl] benzothiazolium iodide (9-PhEBI), were measured in different solvents of various polarity including; H2O, MeOH, EtOH, CH3CN, CH2Cl2 and CHCl3. The photochemical and thermal reactivities were studied in MeOH, EtOH and CH3CN solvents. The molecular aggregation of 9-PhEBI and formation of J-aggregates was observed in the used solvents even at low concentrations. Further aggregation, with changing the color of the dye from pale yellow to violet, was observed in water. Quantum chemical calculations were employed in order to investigate the intramolecular charge transfer (ICT) process and some quantum chemical parameters. A good agreement between the experimental and theoretical results was found.

Graphical abstractThe photochemical and thermal reactivities of a hemicyanine dye, 1-methy-2-[2-(9-phenantheryl)ethenyl] benzothiazolium iodide (9-PhEBI), were studied. The molecular aggregation of 9-PhEBI and formation of J-aggregates was observed in the used solvents even at low concentrations. Further aggregation, with changing the color of the dye from pale yellow to violet, was observed in water. Quantum chemical calculations were employed in order to investigate the direction of the intramolecular charge transfer (ICT) process and some quantum chemical parameters.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights• A hemicyanine dye (9-PhEBI) has been synthesized and investigated spectrophotometrically and theoretically. • 9-PhEBI dye undergoes the formation of molecular aggregates of the J-type in different solvents and adsorbs strongly from aqueous solutions on the glassware, so it may be used as photo-sensitizer in photographic industry. • The quantum chemical calculations have been employed to explain and support the experimental findings.