A density functional theory study of interaction between formamide and guanine

Abstract

Hydrogen bonding in complexes formed between formamide and guanine molecules was completely investigated using density functional theory (DFT) at the 6-311++G(d, p) level. For comparison, the HF and MP2 methods were also used. Nine stable cyclic structures stabilized by two hydrogen bonds were found. One of these was a six-membered ring, five were seven-membered rings, and the others were eight-membered rings. The eight-membered ring is preferable to the seven-and six-membered ones as follows from H-bond lengths and interaction energies. The FG4 structure was calculated to be the most stable, and another cyclic structure, FG5, was least stable because of the six-membered ring and the weakest interaction. The infrared spectrum frequencies, intensities, and vibrational frequency shifts are also reported.