Investigation of N–H⋅⋅⋅H–M Dihydrogen Bonded Interactions in Adenine, Cytosine, Guanine, and Thymine with H–M (M = Li and Na) Complexes: A DFT Study

In this work, we have investigated the dihydrogen bond interaction of adenine, cytosine, guanine and thymine with H–M (M = Li and Na) complexes to reveal the nature of N–H⋅⋅⋅H–M type using density functional theory (DFT). The structural parameters illustrate that the thymine⋅⋅⋅H–Li complex has the smallest dihydrogen bond distance while the analysis of infrared vibrational frequencies confirmed that all the considered structures belong to true local minima. The natural bond orbital (NBO) analysis was done to evaluate the charge delocalization in intermolecular donor-acceptor interaction for all the complexes. The quantum theory of atom in molecule (QTAIM) and non-covalent interaction (NCI)-reduced density gradient (RDG) approaches were used to describe the nature of interaction. Along with molecular electrostatic potential (MEP), we have also studied Mulliken population analysis to explore the existence of dihydrogen bonded interactions. Besides, localized molecular orbital-energy decomposition analysis (LMO-EDA) was also employed to comprehend the dominant energy components and the nature of H⋅⋅⋅H interaction.