LAUSR

Abstract Hydrogen-bonded complexes of acetylene (C 2 H 2 ) and the benzonitrile (C 6 H 5 CN) have been investigated using matrix isolation infrared spectroscopy and DFT computations. The structure of the complexes and the energies were computed at B3LYP and B3LYP+D3 levels of theory using 6–311++G (d, p) and aug-cc-pVDZ basis sets. DFT computations indicated two minima corresponding to the C-H⋯N (global) and C-H⋯π interactions (local) of 1:1 C 2 H 2 -C 6 H 5 CN complexes, where C 2 H 2 is the proton donor in both complexes. Experimentally, the 1:1 C-H⋯N complex identified from the shifts in the C-H and C N stretching modes corresponding to the C 2 H 2 and C 6 H 5 CN sub-molecules in N 2 and Ar matrices. Atoms in Molecules and Natural Bond Orbital analyses were performed to understand the nature of interaction and to unravel the reasons for red-shifting of the C-H stretching frequency in these complexes. Energy decomposition analysis was carried out to discern the various stabilizing and destabilizing components as a result of hydrogen bonding in the C 2 H 2 -C 6 H 5 CN complexes.