Squaraine dyes are well known for their strong absorption in the visible regime. Reports on chiral squaraine dyes are, however, scarce. To address this gap, we here report two novel chiral squaraine dyes and their achiral counterparts. The presented dyes are aggregated in solution and in thin films. A detailed chiroptical study shows that thin films formed by co-assembling the chiral dye with its achiral counterpart exhibit exceptional photophysical properties. The circular dichroism (CD) of the co-assembled structures reaches a maximum when just 25 % of the chiral dye are present in the mixture. The solid structures with the highest relative CD effect are achieved when the chiral dye is used solely as a director, rather than the structural component. The chiroptical data are further supported by selected spin-filtering measurements using mc-AFM. These findings provide a promising platform for investigating the relationship between the dissymmetry of a supramolecular structure and emerging material properties rather than a comparison between a chiral molecular structure and an achiral counterpart.
The authors acknowledge Chidambar Kulkarni for fruitful discussions. Ralf Bovee is thanked for conducting MALDI‐TOF measurements. We acknowledge funding from the Dutch Ministry of Education, Culture and Science (Gravity program 024.001.035).
|Ministerie van Onderwijs, Cultuur en Wetenschap
- circular dichroism
- helical structures
- squaraine dyes
- supramolecular chemistry