Competitive And Cooperative N -> Pi* And N -> Sigma* Interactions In Benzaldehyde-Formaldehyde: Rotational Characterization

The rotational spectrum of the 1 : 1 benzaldehyde-formaldehyde complex has been investigated by pulsed jet Fourier transform microwave spectroscopy combined with ab initio calculations. The two most stable isomers were observed, with the relative abundance ratio N-I/N-II approximate to 3/1 estimated with intensity measurements. Both observed isomers are stabilized by one dominating O=C center dot center dot center dot O tetrel bond (n - pi* interaction) and one secondary C-H center dot center dot center dot O hydrogen bond. Natural bond orbital analysis and electron localization function analysis were applied to characterize the nature of the noncovalent interactions in the target complex.