Nonlinear Optical Properties of Halogenated Aniline Oligomers

High values of the first (b) and second (g) hyperpolarizabilities were obtained for the halogenated oligomers of the three neutral forms of polyaniline (pernigraniline, emeraldine, and leucoemeraldine). For enhancement of the b and g magnitudes, the t-butyl, t-butoxy, and dimethylamine electron donor groups were introduced into various halogenated oligomers. The effect of the oligomer chain size on the b and g magnitude was also investigated by considering the aniline trimers and hexamers. The highest value of the dynamic b hyperpolarizability (1060 nm) for the second-order harmonic generation (SHG) was found for a pernigraniline hexamer containing fluorine and dimethylamine substituents. The highest g hyperpolarizability magnitudes for the third-order harmonic generation (THG) were observed for all halogenated pernigraniline hexamers containing dimethylamine as a substituent. The AM1/TDHF results show that the halogenated aniline-based molecules are promising candidates for applications in nonlinear optics.