Conformational equilibria in acrolein-CO2: The crucial contribution of n → π* interactions unveiled by rotational spectroscopy

Abstract

Using gas phase Fourier-transform microwave spectroscopy complemented by theoretical analysis, this study delivers a comprehensive depiction of the physical origin of the “n → π* interaction” between CO2 with acrolein, one of the most reactive aldehydes. Three distinct isomers of the acrolein-CO2 complex, linked through a C···O tetrel bond (or n → π* interaction) and a C-H···O hydrogen bond, have been unambiguously identified in the pusled jet. Relative intensity measurements allowed estimation on the population ratio of the three isomers to be T1/T2/C1 ≈ 25/5/1. Advanced theoretical analyses were employed to elucidate the intricacies of the noncovalent interactions within the examined complex. This study not only sheds light on the molecular underpinnings of n → π* interactions but also paves the way for future exploration in carbon dioxide capture and utilization, leveraging the fundamental principles uncovered in the study of acrolein-carbon dioxide interactions.