The QTAIM Analysis of the Hydrogen Bonded Structures Between Ethylene Glycol and Hydrochlorothiazide Drug

The quantum theory of atoms in molecule (QTAIM) analyses were performed on the two optimized hydrogen bonded structures formed between an antihypertensive drug (hydrochlorothiazide) and ethylene glycol as a drug carrier. The DFT computations at the B3LYP/6-31+G* level of theory was used to optimize the structures. It was found that complex 1 is much more stable than complex 2 because the ΔE(H-bonding) is greater for 1. The hydrogen bonding formations in both complexes 1 and 2 are exergonic interactions because the ΔG(H-bonding) are negative meaning they are spontaneous intereactions. The ΔH(H-bonding) values are negative indicating the exothermic nature of these H-bonds. According to the results, it is suggested that complex 1 with a much higher ΔE(H-bonding) can possibly be more appropriately formed compared with complex 2. The QTAIM analysis revealed that there are intramolecular electrostatic C-H…O=S, Cl…NH2 and Cl…O=S interactions as well as a six-membered ring formed by two strong intermolecular O-H…O=S and N-H…O-C hydrogen bonds in 1. The QTAIM graph of complex 2 shows two intramolecular C-H…O=S and Cl…O=S interactions together with a six-membered ring formed by the formation of two strong intermolecular hydrogen bonds including C-H…O-C and N-H…O-C hydrogen bonds