Density function B3LYP method has been used to optimize the geometries of the luteolin, cytosine and luteolin-cytosine complexes at 6-31＋G* basis. The vibrational frequencies have been studied at the same level to analyze these twelve complexes, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes was corrected by basis set superposition error (BSSE). By the analysis of complexes interaction energy, charge density, second-order interaction energies E(2), the C-6 is the most stable structure.

Key words: density functional theory, hydrogen bond, basis set superposition error, cytosine, luteolin