Stoichiometric complexes between cyclic phenylazomethines and a dialkyl phosphate for molecular tiling at the air-water interface

The molecular tiling method is proposed as a novel methodology to provide an artificial molecular arrangement at the air-water interface by assembling rigid amphiphilic units like the pieces. In this study, the mixed monolayers of cyclic phenylazomethine (CPA) as a rigid triangle basement and dihexaciecyl phosphate (DHP) as a monolayer-forming component were investigated by pi-A isotherm measurement and Fourier transform infrared (FTIR) spectroscopy in the reflection-absorption mode in order to provide basic knowledge of molecular tiling design. Although the CPA molecules alone cannot form a stable monolayer on water, monolayers of DHP/CPA mixtures showed two-step condensed phases that reflect two kinds of assembling modes of alkyl chains of these components. FTIR spectra of the transferred monolayers indicated specific interaction of the amine part in CPA and the phosphate moiety of DHR pi-A isotherms of the systematic change in the mixing ratio revealed the binding stoichiometry between DHP and the CPA to be 3:1. Interaction of DHP molecules to three basic sites of CPA and matching in cross-sectional area between three DHP molecules and CPA core would result in the stable formation of the 3:1 complex.