Nonlinear optical, optical limiting and structural properties of tetrastyryl derivatives with pyrene and bithiophene

Two tetrastyryl derivatives (S1, S2) were designed and synthesized by Schiff base reaction. The structure and properties of the compounds were characterized by FT-IR, UV–Vis, TG and Z-scan. The structure-activity relationship of S1 and S2 was studied in detail. The combination of large π conjugation and charge transfer gives the two tetrastyryl derivatives strong nonlinear optical properties. Under picosecond pulse excitation at 532 nm with 3 μJ energy, the nonlinear absorption coefficients of S1 and S2 are 6.5 × 10⁻¹² m/W, 9 × 10⁻¹² m/W, respectively. The third harmonic intensities of S1 and S2 are 215 and 25 times that of SiO₂, respectively. S1 and S2 can be used as nonlinear optical materials and have a certain application prospect in the field of laser protection and frequency conversion.