Supramolecular nanowires formed by amphiphilic self-assembly of NAD with cyanine dyes and their redox properties

We have searched for cationic chromophores that form aggregates in the presence of nicotinamide adenine dinucleotide (NAD), and came across a cyanine dye 1. It gives a monomeric absorption peak in methanol at 577 nm. On the other hand, a blue shifted peak is appeared at 520 nm in water, indicating the formation of H-aggregates of the dyes. Addition of NAD⁺ caused decrease in absorption intensity at 520 nm, and a new absorption peak is appeared at 647 nm (J-band) with a strong fluorescence. Transmission electron microscopy (TEM) reveals the formation of developed nanowires with bundled 1/NAD⁺ complexes (width; ca. 6-8 nm, length; several microns). On the other hand, such assemblies are not formed from the pair of 1/NADH. The present supramolecular systems would be applicable to the redox-switched formation of fluorescent nanowires.