Exploring Uncharted Territory: Spectroscopic Evidence on a Novel Tetrel Bond with -C≡C- Triple Bond.

This study presents an investigation of the 2-butynyl alcohol···CO 2 adduct, combining pulsed jet Fourier transform microwave spectroscopy with quantum chemical calculations. Two distinct isomers have been observed in the pulsed jet with a relative population ratio of 3/2. It marks the first instance of microwave spectroscopic evidence, to the best of our knowledge, suggesting the existence of a C CO 2 ···π -C≡C- tetrel bond (π -C≡C- ···π* CO 2 interaction) in both observed isomers. This study highlights the importance of noncovalent interactions involving CO 2 in reactant complexes, paving the way for more efficient applications of CO 2 by understanding the physical basis of these noncovalent bonds.