A theoretical study on intermolecular hydrogen bonds of isopropanol-water clusters.

In this work, the possible molecular association structure in isopropanol-water solution has been analyzed by density functional theory (DFT) calculations. The properties of the isopropanol-water clusters with different number of water molecules, including optimal structure, intermolecular hydrogen bonding, binding energy and theoretical Raman spectra, are particularly investigated in the gas phase with B3LYP/6–31 + G (d, p) basis set. According to the simulated optimal structure, we found that the influence of hydration in the molecular configuration of isopropanol is mainly reflected in the O–H bond, which increases with the augment of water molecules. Meanwhile, in terms of the most stable structure, isopropanol-(H2O)5 will show the transition from a two-dimensional planar ring structure to a three-dimensional cage structure. In addition, the position and intensity of intermolecular hydrogen bonds interaction between the isopropanol and water molecules have been investigated by atoms in molecule (AIM) analysis and reduced density gradient (RDG) methods. The theoretical Raman spectra of isopropanol-(H2O)n (n = 1–5) clusters show the redshifts of the O–H bond tensile peak, which indicates that the O–H tensile strength is weakened and the hydrogen bonds interaction is strengthened with the increase in water molecules. [ABSTRACT FROM AUTHOR]