π‐hole driven N⋅⋅⋅O/N⋅⋅⋅π Pnicogen and C⋅⋅⋅O Tetrel Bonding inNitromethane‐Carbonyl Dimers: Comprehensive Study using Matrix Isolation Infrared Spectroscopy and Quantum Chemical Computations

Abstract

The geometries of nitromethane‐carbonyl dimers were investigated comprehensively with formaldehyde, acetaldehyde and acetone as model Lewis bases. Pnicogen bonding involving nitrogen of nitromethane was discerned to be a stabilizing interaction along with hydrogen and tetrel (carbon) bonding interactions in all these dimers. The structures of the dimers generated at low temperatures under isolated conditions were established using infrared spectroscopy with the aid of ab initio and DFT computations. The existence of C−H⋅⋅⋅O hydrogen, O=N⋅⋅⋅O, O=N⋅⋅⋅π pnicogen and O=C⋅⋅⋅O tetrel bonding was asserted from Quantum Theory of Atoms In Molecules (QTAIM), Natural Bond Orbital (NBO), Electrostatic Potential (ESP) mapping and Non‐Covalent Interaction (NCI) analyses. Methyl substitution on formaldehyde results in the instigation of steric effect which was found to have a profound influence on the geometries of heterodimers of nitromethane‐acetaldehyde and nitromethane‐acetone. The plausible role of steric effect on pnicogen and tetrel bonding was probed through the analysis of nature of interactions in these nitromethane‐carbonyl dimer systems.