Benzo[1,2-b:4,3-b']dithiophene-pyridine isomers: Synthesis, self-assembly, photophysical and acidochromic properties

Two benzo[1,2-b:4,3-b']dithiophene-pyridine-based bent shaped isomers (3BDTPy12 and 4BDTPy12) have been synthesized via Suzuki coupling reactions as key steps. They differ themselves in the position of N-atom on the pyridine unit which has generated significant effect on their self-assembly behavior and photophysical properties. 4BDTPy12 with N in the para position in the pyridine ring can self-assemble into a columnar liquid crystalline phase while its isomer 3BDTPy12 with N in the meta position in the pyridine ring is only a crystal. Both compounds can form gels in different organic solvents but with different morphologies. The influence of the solvent polarities and doping agents including chiral L-phenylalanine (L-Phe), trifluoroacetic acid as well as L tartaric acid on their gel morphologies were also studied. The gel of 4BDTPy12 doped with L-tartaric acid could produce enhanced yellow emission which can be used to generate WLED, and such compounds can be used as chemosensors towards volatile acid-base vapors with good reversibility.