The rotational spectrum of the 1:1 benzaldehyde-CO2 complex has been investigated by pulsed-jet Fourier transform microwave spectroscopy complemented with quantum chemical calculations. Two isomers, both characterized by one C···O tetrel...

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The rotational spectrum of 2‐methoxypyridine⋅⋅⋅CO2 was recorded and analysed employing a cavity‐based Fourier transform microwave spectrometer, complemented with quantum chemical calculations which predicted three possible isomers within energies less than 1000 cm−1. The two most stable isomers were observed in the pulsed jet, which are stabilized by a network of C⋅⋅⋅N/O tetrel and C−H⋅⋅⋅O weak hydrogen bonds. The relative population ratio of the two detected isomers was estimated to be NI/NII≈2.5. The competition and cooperation of the present non‐covalent interactions in both isomers are discussed within the framework of Bader's quantum theory of atoms in molecules and Johnson's non‐covalent interaction analyses. The study shows, that when looking for CO2 adsorbents, one might prefer candidates with multiple interactions in one site over candidates with few but strong interactions.

The rotational spectrum of acetoin (3-hydroxy-2-butanone) was measured by using Fourier transform microwave spectroscopy with the aid of quantum chemical calculations. Only one conformer of acetoin was detected in the pulsed jet, whose spectrum featured the splittings raised from the internal rotation of the methyl top linking to the CO group. Based on the spectroscopic result, radio-astronomical searches for acetoin were carried out toward the massive star-forming region Sgr B2­(N) using the Shanghai Tianma 65 m and IRAM 30 m radio telescopes. No lines belonging to acetoin were detected toward Sgr B2­(N). Its upper limit of column density was calculated.