A computational comparison into the cation–π interaction and its effect on the intramolecular hydrogen bond in the different complexes of 5-Aminosalicylic acid with its thio analogous

The effects of non-covalent interactions on the strength and nature of the 5-Aminosalicylic acid complexes and its thio analogous are investigated at the ωB97XD/6-311++G(d,p) level of theory. The atoms in molecules and the natural bond orbital analyses are applied for a better understanding of these interactions. The results show that the cation-π interactions in the monovalent complexes have a stronger influence on the HB strength with respect to those in the divalent complexes. The replacement of oxygen by sulfur atoms increases the hydrogen bond strength in the complexes. Based on the molecular orbital data, the Li+ complexes with the larger energy gap are more stable and harder, while the Mg2+ complexes with the lower energy gap are more reactive and thus softer.