Donor–acceptor molecules based on benzothiadiazole: Synthesis, X-ray crystal structures, linear and third-order nonlinear optical properties

Abstract

Three π-conjugated donor–acceptor molecules containing either N,N-dimethylaniline or carbazole as the electron donor and 2,1,3-benzothiadiazole as the electron acceptor were synthesized through either Suzuki or Sonogashira cross-coupling reactions. Their X-ray crystal structural, optical, electrochemical properties were investigated. These compounds showed blue-shifted emission in the solid state compared with those in organic solvents. HOMO–LUMO gaps of these compounds estimated from cyclic voltammetry experiments correlated well with those obtained from theoretical calculation results. The nonlinear optical properties of the three D–A molecules were studied using the top-hat Z-scan technique with 21 ps laser pulses at 532 nm. The compound with N,N-dimethylaniline as the donor featuring a more planar configuration makes π-electrons more delocalized, which exhibited large third-order nonlinear absorption and refraction effect.