Hydrogen-Bond-Directed Formation of Supramolecular Polymers Incorporating Head-to-Tail Oriented Dipolar Merocyanine Dyes

A self-complementary Hamilton-receptor-functionalized merocyanine dye has been synthesized by incorporating a hydrogen bonding receptor site to the donor moiety of a merocyanine chromophore that bears a barbituric acid acceptor unit. The optical and electro-optical properties of monomeric dyes have been studied by UV-vis, fluorescence, and electro-optical absorption spectroscopy in chloroform, 1,4-dioxane, tetrahydrofuran, and dimethyl sulfoxide under dilute condition. The self-assembly properties of this self-complementary merocyanine in solution have been investigated by concentration-and temperature-dependent UV-vis and one- and two-dimensional NMR spectroscopy. These studies revealed that the present merocyanine dyes self-assemble in a head-to-tail fashion by forming six hydrogen bonds. The size of the assemblies in solution was determined by dynamic light scattering and diffusion-ordered spectroscopy NMR investigations. In nonpolar solvent mixtures at high concentrations, this merocyanine dye forms appreciably fluorescent gels (Phi(fl) = 0.17) while the monomeric dye and self-assemblies in solution are only weakly fluorescent (Phi(fl) = 0.07).