Synthesis, modelling, and solvatochromic properties of a phenothiazine derivative

Abstract

A new A-π-D-π-A phenothiazine derivative, 2,2'-((10-octyl-10H-phenothiazine-3,7-diyl)bis (ethene-2,1-diyl))bis(1-ethyl-3,3-dimethyl-3H-indol-1-ium)iodide (PTZ-BEI) was prepared and fully characterized using infra-red (IR), ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, ultraviolet-visible light and mass spectra. Electronic spectra of PTZ-BEI solutions in solvents with different polarities displayed absorption bands (λ_max ) related to intramolecular charge transfer. In addition, the emission spectra of PTZ-BEI solutions were strongly solvent dependent for both wavelength and intensity. Stokes' shift ( $\Delta \overline{\nu })$ increased with increasing solvent polarity up to 4105 cm^-1 in the most polar solvent, dimethylformamide. The linear solvation-energy relationship was utilized to investigate solvent dependency of the Stokes' shifts. Relative quantum yield (φ) of PTZ-BEI was calculated. Finally, density functional theory was employed at the B3LYP level for geometrical optimization and simulation of electron spectra for the PTZ derivative in gaseous and solvated states to explore the solvent effect.

Keywords: PTZ-BEI; fluorescence; modelling; solvatochromic.