Luminescent Co-Assemblies of Donor-Acceptor Dimeric Cyanostilbenes with (Bio)Anionic Polymeric Templates.

Amphiphilic dimeric cyanostilbenes with two donor-acceptor moieties connected through variable aliphatic linkers displayed aggregation in aqueous media to produce red emissive nano-assemblies. In the presence of anionic biopolymers such as ctDNA and heparin, they formed electrostatically driven co-assemblies with enhanced luminescence. Moreover, due to the chiral nature of the bio-templates DNA and heparin, the co-assemblies demonstrated induced chirality features. Although the central double bond in cyanostilbenes is known to undergo various photochemical conversions, these dimeric donor-acceptor cyanostilbenes, in their self-assembled state, essentially remained photoinactive under UV irradiation. However, in the bio-templated co-assemblies, they showed comparatively higher photo-reactivity, which was especially prominent for the ctDNA based co-assemblies. We also found that these co-assemblies can be used as artificial light-harvesting systems by incorporating acceptor dyes and this led to the generation of amplified emission from the acceptor dyes in the NIR range of the spectrum. Furthermore, the co-assemblies demonstrated selective fluorescence quenching in the presence of metal ions such as Cu and Fe, highlighting their potential for metal-ion sensing applications.