Conjugated Thiophene-Fused Isatin Dyes through Intramolecular Direct Arylation

We
report on the design, synthesis, and properties of innovative,
planar, π-conjugated compounds in which a thiophene ring is
fused with the skeleton of the naturally occurring dye isatin. The
synthesis is achieved in high yields making use of an intramolecular
direct arylation reaction as the key step, making the overall process
potentially scalable. The synthetic sequence has been demonstrated
also for an isatin bearing fluorine substituents on the aromatic ring.
NMR and X-ray studies demonstrate the crosstalk occurring between
the fused, coplanar, and conjugated moieties, making these novel dyes
with a donor–acceptor character. Cyclic voltammetry and UV–vis
studies confirm very interesting HOMO–LUMO levels and energy
gaps for the new compounds.