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 and 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 pulsed 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.