Facile synthesis of benzothiadiazole-based chromophores for enhanced performance of second-order nonlinear optical materials

Abstract

Novel benzothiadiazole-based second-order nonlinear optical (NLO) chromophores with different push–pull structures were developed. Incorporation of benzothiadiazole (BTD) as a bridge for improving the electro-optic (EO) coefficient (r₃₃) of bulky materials has not been well investigated, despite its extensive application in other photonic materials as electron acceptor. NMR and MS have been used to characterize the structure of synthesized chromophores 5–7. Optical properties have been investigated by UV-vis spectra. Density functional theory calculations have been used to calculate the first-order hyperpolarizability (β) of chromophores r1, 5a, 7a and 5b. Moreover, the poling results of guest–host EO polymers, 5a/PC and 5b/PC, afforded good r₃₃ values of 67 pm V⁻¹ and 45 pm V⁻¹, respectively. All the results demonstrated an improvement in both micro- and macroscopic nonlinearity after incorporation of BTD into chromophores.