Multivalent-Anion-Induced Inversion of Chiroptical Signals in a Cyanine Dye Bound to Nanotubular Supramolecular Assemblies
Year: 2026
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide In this study, we investigated the effect of salts on the induced chirality of the cyanine dye NK2707 when bound to supramolecular assemblies formed by cationic glutamide lipids (G-Py + ). NK2707 bound to G-Py + self-assembled structures formed diverse aggregates and exhibited exceptionally large circular dichroism (CD) signals. The J -aggregates of NK2707 showed an unusually intense R -chiral-induced CD signal attributable to Davydov splitting; this signal reversed to an S -chiral CD response upon addition of the sodium salt of a multivalent anion. This inversion of a CD signal at the 10 6 level is unprecedented. In contrast, NaCl addition produced no appreciable spectral change, suggesting that this effect strongly depends on anion valence. We attribute the CD inversion to multivalent-anion bridging of pyridinium groups, which alters and stabilizes the chiral orientation of G-Py + and, in turn, reverses the induced CD. Furthermore, although molecular orientation typically decreases above the gel–liquid-crystal phase transition temperature, Na 2 SO 4 addition enabled G-Py + to retain its chiral orientation even in the liquid-crystal state. Na 2 SO 4 promoted J -aggregate formation in the gel state and H -aggregate formation in the liquid-crystal state, maintaining a CD peak on the order of 10 6 while shifting the wavelength by approximately 200 nm. Overall, the G-Py + /NK2707 system can be dynamically modulated by multivalent anions and temperature, providing a versatile platform for controlling chiroptical properties through salt-induced changes in molecular orientation.
Source: Langmuir
Institution: Kumamoto University
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W7167014498