Molecular recognition at the air—water interface and Langmuir—Blodgett films

The novel amphiphile 9-octadecyladenine (AdC18), which has an adenine headgroup and a long hydrocarbon chain, was synthesized. Its monolayer behavior and its interactions with three guest molecules were investigated at the air—water interface by means of surface pressure—area isotherms. The structures of multilayer Langmuir—Blodgett (LB) films of AdC18 were characterized by Fourier transform IR spectroscopy. When the monolayer was transferred from a uridine aqueous solution to a solid substrate, the IR spectra varied significantly from the spectrum of the film transferred from the pure water subphase. Shifts of band positions and particularly the appearance of a broadened band demonstrated that guest molecules were transferred to the solid substrate along with the AdC18 monolayer and that hydrogen bonds were formed between complementary nucleobases within the LB films.