A dithieno[2,3-b:3',2'-d]thiophene bridged D-A compound, (E)-N-4-(2-(5-dicyanovinly-dithieno[2,3-b:3',2'-d]thiophene-2-yl)-ethenyl)-N,N-diphenylamine (TPA-DCST) was synthesized and its spectroscopic behaviors were studied. In the section of synthesis, TPA-DCST was synthesized by Wittig reaction between two moieties of triphenyl amine and dithieno[2,3-b:3',2'-d]thiophene-2-carbaldehyde, and the following formylation of dithieno[2,3-b:3',2'-d]thiophene moiety and Knoevenagel condensation with malononitrile. The target compound TPA-DCST was fully characterized by 1HNMR, 13CNMR, IR and HRMS. In the section of the spectroscopic behaviors, both absorption and emission behaviors of TPA-DCST were studied. The absorption peak at ~412 nm belongs to π-π* transition. TPA-DCST shows an interesting broad emission at 550 nm in diluted hexane solution, which is regarded as an emission from molecular aggregation, and confirmed by its single peak emission at 460 nm in CTAB micelle solution ([c]=1.02×10-2 mol/L). No ICT emission was observed in different polar solvents, because the conjugation bridge, dithieno[2,3-b:3',2'-d]thiophene does not show the effective function of conjugation due to the molecular structure itself. Both concentration effect and temperature effect show that TPA-DCST molecules are easy to give the emission from molecular aggregation. In THF-H2O binary mixture solution, TPA-DCST shows typical AIE state emission at 692 nm. With increasing aggregation of TPA-DCST molecules, the emission peak shows strong bathochromic shift, from 550 nm in hexane solution to 710 nm in solid. The driving force of the aggregation may be from hydrophobic effect and dipole-dipole interaction of TPA-DCST molecules.
