The molecular modeling analysis via density functional theory is performed on all the formed complexes from interaction between mono and divalent metal cations (Li+, Na+, K+, Be2+, Mg2+, and Ca2+) with acetaminophen. The interaction energies are calculated at B3LYP/6-311++G** level using the Gaussian 03 program package. The investigated structures are analyzed by topological parameters in terms of electron density (?) and its Laplacian (?2?) at the bond critical point (BCP) using the atoms in molecules (AIM) methodology. The obtained results from DFT and AIM calculations suggest that the strongest interaction and the highest electron density at BCP is related to the Be2+ complex.
In addition, the natural bond orbital (NBO) analysis is performed to analyze the charge distribution in the related complexes. The influence of cation–? interaction on the strength and nature of C–H???C intramolecular hydrogen bond are also analyzed in the studied complexes. The results show that the C–H???C hydrogen bond are strengthened by the cation–? interactions in the monovalent complexes. The quantum molecular descriptors such as energy gap, chemical potential, global hardness, softness and electrophilicity index are also calculated. In addition, the MEP is given the visual representation of the chemically active sites and comparative reactivity of atoms