Synthesis, linear and nonlinear optical properties of a new dimethine cyanine dye derived from phenothiazine

Dimethine cyanine dye (PTZIS) based on phenothiazine as the core donor and indolium salt as the acceptor has been synthesized and fully characterized. UV-Vis absorption and fluorescence properties of PTZIS were studied in different solvents. Absorption spectra revealed a large bathochromic shift of the intramolecular charge transfer (ICT) absorption band of PTZIS compared with those in the non-halogenated solvents. Also, the optical data of PTZIS showed a large Stokes shift compared with those in the non-halogenated solvents, indicating a great influence on the geometry of the emissive excited state. The nonlinear optical properties of PTZIS in ethanol solution at different concentrations and different laser powers have been studied using the Z-scan technique with a continuous wave (cw) argon ion laser at 514.5 nm. The closed aperture Z-scan data was used to estimate the nonlinear refractive index n2, while the open aperture scan provided the nonlinear absorption coefficient β. The values obtained are relatively very high and vary linearly with concentration.