Molecular recognition of adenine, adenosine and ATP at the air–water interface by a uracil appended fullerene

A new C60-uracil adduct capable of hydrogen bonding, via complimentary base pairing, of adenine, adenosine, and adenosine 5′-triphosphate (ATP) was synthesized and characterized by UV-visible and 1H NMR spectroscopy, cyclic voltammetry and differential pulse voltammetry, as well as ESI-mass spectrometry. Molecular modeling by ab initio B3LYP/3–21G(*) calculations revealed the Watson–Crick type base pairing. Stable “expanded liquid” Langmuir films of the C60-uracil–adenine, C60-uracil–adenosine and C60-uracil–ATP complexes were prepared and characterized by isotherms of surface pressure versus area per molecule as well as the Brewster angle microscopy imaging. The area per molecule at infinite adduct dilution in the film was dependent on composition of the subphase solution and increased in the order: water < adenine < adenosine < ATP solution. Comparison of experimental and calculated areas per molecule and dipole moment components normal to the subphase–air interface indicated prevailing horizontal orientation of the complexes in the films. The Langmuir films were transferred, by using the Langmuir–Blodgett technique, onto quartz slides and characterized by the UV-visible spectroscopy.