Melting of Hydrogen Bonds in Uracil Derivatives Probed by Infrared Spectroscopy and ab Initio Molecular Dynamics

The thermal response of hydrogen bonds is a crucial aspect in the self-assembly of molecular nanostructures. To gain a detailed understanding of their response, we investigated infrared spectra of monomers and hydrogen-bonded dimers of two uracil-derivative molecules, supported by density functional theory calculations. Matrix isolation spectra of monomers, temperature dependence in the solid state, and ab initio molecular dynamics calculations give a comprehensive picture about the dimer structure and dynamics of such systems as well as a proper assignment of hydrogen-bond affected bands. The evolution of the hydrogen bond melting is followed by calculating the C═O···H–N distance distributions at different temperatures. The result of this calculation yields excellent agreement with the H-bond melting temperature observed by experiment.