Theoretical investigation of the nature of hydrogen bonds and cooperativity effect in methanol-water and ethanol-water clusters

ABSTRACT

This study aims to cast light on the nature of hydrogen bonds and their cooperativity that exists in alcohol-water ($\text{ROH}({\text{H}}_2\text{O}{)}_{\text{n}}$) ($\text{R}=-\text{C}{\text{H}}_3\left(-\text{Me}\right),-\text{C}{\text{H}}_2\text{C}{\text{H}}_3\left(-\text{Et}\right)$) (n = 1–10) clusters using atoms in molecules (AIM) theory and symmetry-adapted perturbation theory (SAPT). The investigation of optimum structures suggests that alcohol ($\text{ROH}$) forms two hydrogen bonds, one primary hydrogen bond $\left(\text{O}-\text{H}\cdot \cdot \cdot \text{O}\right)$, and one secondary hydrogen bond $\left(\text{C}-\text{H}\cdot \cdot \cdot \text{O}\right)$ Two types of hydrogen bonds are addressed in these studies, where alcohol works as the hydrogen bond donor $\left(\text{ROH}\cdot \cdot \cdot \text{O}{\text{H}}_2\right)$ and hydrogen bond acceptor $\left(\text{RHO}\cdot \cdot \cdot \text{HOH}\right)$. The AIM results reveal that $\text{RHO}\cdot \cdot \cdot \text{HOH}$ and $\text{ROH}\cdot \cdot \cdot \text{O}{\text{H}}_2$ hydrogen bonds are partially covalent. The SAPT study demonstrates that in all the clusters studied herein, the electrostatic interaction between alcohol and water is the main attractive force, and its contribution may be two times larger than the separate corresponding contributions from the dispersion and the induction terms. The electron density (ρ) at the bond critical point (BCP) is a suitable parameter to assess the strength of the interaction. The current study shows the strength and nature of $\text{ROH}\cdot \cdot \cdot \text{O}{\text{H}}_2$ and $\text{RHO}\cdot \cdot \cdot \text{HOH}$ hydrogen bond, and cooperative effect in ($\text{ROH}({\text{H}}_2\text{O}{)}_{\text{n}}$) ($\text{R}=-\text{C}{\text{H}}_3\left(-\text{Me}\right),-\text{C}{\text{H}}_2\text{C}{\text{H}}_3\left(-\text{Et}\right)$.) (n = 1–10).

GRAPHICAL ABSTRACT

KEYWORDS:

• Cooperativity
• covalent bond
• electron density
• interaction energy
• symmetry-adapted perturbation theory

Acknowledgment

The author thanks the Indian Institute of Technology Patna for providing research facilities at IIT Patna.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Council of Scientific and Industrial Research of India (Grant No.01 (2890)/17/EMR-11) and the Prime Minister Research Fellowship (Id-2702447) Ministry of India.