Unravelling the origin of strong non-reciprocal chiroptical features in thin films of a chiral diketopyrrolo[3,4-c]pyrrole dye

The development of chiral organic materials with strong non-reciprocal chiroptical features may have major implications for cutting-edge technological applications. In this work, a new ad hoc synthesized chiral 1,4-diketo-3,6-dithienylpyrrolo[3,4-c]pyrrole dye, bearing two (S)-3,7-dimethyl-1-octyl alkyl chains on the lactam moieties and functionalized with two lateral 9-anthracenyl π-conjugated units, exhibited strong non-reciprocal chiroptical properties in thin films, with some important differences between samples prepared by drop casting and spin coating. A detailed study was performed to unravel the intimate structure-property relationship, involving computational analysis, different microscopy techniques and synchrotron radiation Mueller matrix polarimetry imaging (SR-MMPi) investigation. Through SR-MMPi, exploiting the highly collimated synchrotron radiation (SR) light of Diamond Light Source B23 beamline, we determined the size of the linear contributions responsible for the strong non-reciprocal features, and how they manifest in the various 2D chiral meso-domains.