Strong Non‐Reciprocal Chiroptical Properties in Thin Films of Chiral Alkylthio‐Decorated 1,4‐Phenylene/Thiophene Dyes

Abstract

In the context of chiral π‐conjugated materials, the use of enantiopure alkylthio appendages represents a valid alternative to conventional alkoxy groups: sulphur atom is bigger and more electron‐rich than oxygen, thus allowing for higher polarizability, greater flexibility, larger bulkiness and lower structural anisotropy. In light of these considerations, here we report two new chiral alkylthio‐decorated 1,4‐phenylene/thiophene dyes, obtained by simple synthetic strategies involving Pd‐catalyzed cross‐coupling protocols, looking for strong non‐reciprocal chiroptical features in thin films. In particular, for the chiral alkylthio‐decorated 1,4‐phenylene–bis(thiophenylpropynone) (Thio‐PTPO) dye, which proved to be the most promising for our purpose, a detailed investigation in thin films was carried out, involving optical and chiroptical spectroscopies in absorption and emission, as well as optical microscopy techniques.