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···CO2 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 CCO2···π-C≡C- tetrel bond (π-C≡C-···π*CO2 interaction) in both observed isomers. This study highlights the importance of noncovalent interactions involving CO2 in reactant complexes, paving the way for more efficient applications of CO2 by understanding the physical basis of these noncovalent bonds.