Growth Pattern, Stability, and Properties of Complexes of C₂H₅OH and nCO₂ (n = 1-5) Molecules: A Theoretical Study

This work is dedicated to theoretically investigate the formation process of C₂H₅OH···nCO₂ (n = 1-5) complexes and to shed light on the nature of interactions formed under the variation of CO₂ concentration. It is found that CO₂ molecules tend to locate around the polarized -OH group to interact with the lone pairs of the O atom. The interaction of ethanol with three CO₂ molecules (C₂H₅OH···3CO₂) induces the most stable structure in the sequence considered. The atoms in molecules (AIM), NCIplot, and natural bond orbital (NBO) analyses point out that the O_ethanol···C_CO tetrel bond overcomes hydrogen, chalcogen, and CO₂···CO₂ tetrel-bonded interactions and mainly contributes to the strength of C₂H₅OH···nCO₂ (n = 1-5) complexes. All intermolecular interactions in the examined complexes are weakly noncovalent, and their positive cooperativity is evaluated to be slightly weaker than that of CO₂ pure systems. SAPT2+ and molecular electrostatic potential (MEP) calculations indicate that the electrostatic force is the main factor underlying the attractive interplay in the complexes of C₂H₅OH and CO₂.