Synthesis and nonlinear optical properties of 4-phenylethylene derivatives based on a large π conjugated structure

4-phenylethylene derivatives (B1, B2 and B3) with π conjugated systems were designed and synthesized by Sonogashira coupling reaction and Schiff base reaction. Under the ns laser source, the nonlinear absorption coefficients (β) of B2 and B3 are 1.85 × 10⁻¹⁰ m/W and 1.9 × 10⁻¹⁰ m/W. B2 and B3 have good light limit performance. Furthermore, the third harmonic strength of B2 and B3 is 181 and 215 times that of SiO₂, respectively. The optical limiting threshold and third harmonic signal show that 4-phenylethylene derivatives will have good application potential in laser protection and frequency conversion.