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

Three pi-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 pi-electrons more delocalized, which exhibited large third-order nonlinear absorption and refraction effect. (C) 2015 Elsevier Ltd. All rights reserved.