Rotational spectrum and theoretical calculations of pyrazole⋯CO2 complex: Tetrel and hydrogen bond interactions.

The complex between pyrazole and carbon dioxide has been generated in a supersonic jet and characterized using Fourier transform microwave spectroscopy and state of the art CCSD(T) theoretical calculations. The complex presents a planar configuration showing a simultaneous N⋯C=O n → π* tetrel bond and a NH⋯O hydrogen bond. The TS internal rotation barrier that interconverts the oxygen atoms of CO2 has been calculated to be 10 kJ mol-1 at the CCSD(T) level. The electronic characteristics of the minimum and TS have been analyzed. Machine learning methods have been applied to predict the potential energy surface of the pyrazole⋯carbon dioxide complex.