Theoretical studies of interactions between imidazopyridopyrimidines and guanine

The intrinsic contributions to the stabilization of imidazopyridopyrimidine-containing DNA duplexes, which are new, promising unnatural DNA motifs, were discussed. The MP2/6-31 G*(0.25) interaction energies for the optimal HF/6-31G** hydrogen-bonding arrangements of the complexes between the respective imidazopyridopyrimidine derivatives and guanine covered the range from -60.0 to -101.7 kJ/mol. The MP2/6-31 G*(0.25) stacking energies were investigated for a variety of vertical and angular orientations. For some of them, the stacking interaction was found to be competitive to the hydrogen-bonding.