Benzimidazole-thiazole based NLOphoric styryl dyes with solid state emission – Synthesis, photophysical, hyperpolarizability and TD-DFT studies

• Novel push–pull type of styryl derivatives from thiazole carbaldehyde.
• Photophysical properties of styryl derivatives supported by TD-DFT computational data.
• Dye 6b shows good fluorescence intensity in solid state, dye 6c shows red shifted absorption and emission.
• Non-linear optical properties using solvatochromic method and density functional theory in different polarities of solvent.

Multi-step synthesis was achieved to obtain new generation push–pull dyes containing benzimidazole fluorophore and thiazole unit. A largest Stokes shift of 114 nm in acetonitrile is observed in extended styryl among all the dyes. Density functional theory and time dependent-density functional theory computations have been used for comparative study with the experimental data and also to understand the substitution or steric effect on structural, molecular, electronic and photophysical parameters of the benzimidazole fluorophore of the thiazole based styryl dyes. First-order hyperpolarizability, using solvatochromism and solvent dependent shifts in emission wavelengths and the transition dipole moments were used to characterize and evaluate the second-order nonlinear optical performances of the styryl dyes in different organic solvents. The density functional theory method was also employed to investigate the non-linear optical properties of the styryl dyes in different solvent media. The substituted benzimidazolyl thiazolestyryl dyes possess good non-linear optical properties.

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