Theoretical aspects of cooperativity and hydrogen bond in complexes of adenine and two formaldehyde molecules

Abstract

AbstractIn the present work, we use quantum chemical calculations to investigate the strength, origin and role of hydrogen bonds as well as their cooperativity in complexes of adenine with two formaldehyde molecules. Eight stable structures of complexes are determined on potential energy surface at the B3LYP/aug‐cc‐pVDZ level of theory. The interaction energies of complexes with ZPE and BSSE corrections range from ‐4.45 to ‐9.45 kcal.mol‐1. The NBO and AIM analyses indicate that the strength of complexes is mainly governed by the N‐H‧‧‧O hydrogen bonds predominating O=C‧‧‧O and C‐H‧‧‧O/N intermolecular interactions. Besides, the C‐H‧‧‧O/N contacts are blue shifting hydrogen bonds, while the red shift of N‐H stretching frequency occurs in N‐H‧‧‧O hydrogen bonds in the complexes investigated. Noticeably, it is found that the positive cooperativity makes an increase in the complex stability and the C‐H blue shift of stretching frequency in C‐H‧‧‧O hydrogen bonds upon complexation.