Synthesis and Tuning Optical Nonlinear Properties of Molecular Crystals of Benzothiadiazole

We described the synthesis and characterization of four kinds of donor−acceptor systems of benzothiadiazole derivatives (BTDs). The crystal packing styles of BTDs can be tuned from the centrosymmetric triclinic crystal system to the noncentrosymmetric orthorhombic system. The nonlinear absorption and nonlinear refraction of BTDs were studied by using the Z-scan technique at 532 nm at 4 ns pulse. The results indicated that all of them exhibit third-order nonlinear optical properties including nonlinear absorption and refractive effects.