Squaraine dyes are well knownf or their strong absorption in the visible regime. Reports on chiral squaraine dyes are, however,s carce. 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. Ad etailed chiroptical study shows that thin films formed by co-assembling the chiral dye with its achiral counterparte xhibit exceptionalp hotophysical properties. The circulard ichroism (CD) of the co-assembled structures reaches am aximum when just 25 %o ft he chiral dye are present in the mixture. The solid structures with the highestr elative CD effect are achieved when the chiral dye is used solely as ad irector,r ather than the structural component. The chiroptical data are further supported by selected spin-filtering measurements using mc-AFM.T hese findings provideapromisingp latform for investigating the relationship between the dissymmetry of as upramolecular structure and emerging material properties rather than ac omparison between ac hiral molecular structure and an achiral counterpart.
The conformational
analysis of a 2,4-bis(4-dialkylamino-2-amido)phenyl
squaraine dye revealed the presence of two rotational isomers at room
temperature. Combination of spectroscopic and computational techniques
showed that the rotational barrier is influenced by hydrogen bonds
between the amido substituents and the oxygen atoms at the quadratic
core. Even small amounts of trifluoroacetic acid interfered with the
intramolecular hydrogen bond formation and accelerated the interconversion
of the conformers.
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