Self-Assembled Spiral Nanoarchitecture and Supramolecular Chirality in Langmuir-Blodgett Films of an Achiral Amphiphilic Barbituric Acid
Xin Huang, Chao Li, Siguang Jiang, Xuesong Wang, Baowen Zhang, and Minghua Liu*,
Langmuir-Blodgett films of an achiral molecule, an amphiphilic derivative of barbituric acid, were observed to form arrays of spiral structures. Monolayers of the molecule was formed at the air/water interface and showed a clear phase transition. After the phase transfer region, the monolayer was transferred onto solid substrates and the circular dichroism spectra and atomic force microscope (AFM) was measured. It was found that although the amphiphile itself was achiral, it formed chiral assemblies. Furthermore, a spiral structure was observed in the AFM pictures. It was suggested that the close packing of the aromatic rings of the head groups and the directionality of hydrogen bonding interactions induced a preferential tilting of neighboring molecules and thus produced the chirality and spirals.