Second harmonic generation and the photoelectric property studies on a new dye, (E)-N-octadecyl-4-[2-(4-dimethylaminophenyl) enamine] pyridinium iodide

According to quantum chemistry calculation, a Schiff-base (E)-N-octadecyl-4-[2-(4-dimethylaminophenyl) enamine] pyridinium iodide with a large dipole moment difference between the excited state and the ground state (Δμ), is designed and synthesized as a second-order non-linear optical material. Its second-order susceptibility (χ_zzz⁽²⁾) is evaluated to be 279.4 pm V^-1, which is larger than that of the hemicyanine which is known as one of the best dyes in the second harmonic generation (SHG) behavior. Its LB film formation properties were studied. The photoelectric conversion property is not as good as expected. According to the experiments and the results of the quantum chemistry calculation, an explanation of this phenomenon is proposed.