Hydrogen-Bonding Interaction in a Complex of Amino Acid with N,N-Dimethylformamide Studied by DFT Calculations

Abstract

Theoretical studies on hydrogen-bonded complexes between amino acids (glycine, alanine and leucine) and N,N-dimethylformamide (DMF) in gas phase have been carried out using density functional theory (DFT) and ab initio calculations at the B3LYP/6-311++G** and MP2/6-311++G** theory levels. The structures, binding energy, stretching frequency and bond characteristics of the mentioned complexes were calculated. The NH2 and COOH groups of amino acids form different types of hydrogen bonds with the DMF molecule, as well as alkyl side chains. High binding energy suggests multiple hydrogen bonds present in one complex. The nearly linear OH⋅⋅⋅O and NH⋅⋅⋅O contacts are stronger than a conventional hydrogen bond interaction with their H⋅⋅⋅O separation between 1.74 and 2.14 A. The weaker CH⋅⋅⋅O H-bond is also discussed as being a crucial interaction in biological systems involving amino acids. The formation of this interaction results in a blue shift in the CH stretching frequency.